Male Hypogonadism

1. Clinical Overview

Summary

Male Hypogonadism is a clinical syndrome resulting from the inability of the testes to produce physiological levels of testosterone (androgen deficiency) and/or a normal number of spermatozoa (impaired spermatogenesis). It is a common but often undiagnosed condition, affecting up to 6-12% of men aged 40-69 years. The condition is classified into Primary (Testicular failure; Hypergonadotropic) and Secondary (Hypothalamic-Pituitary failure; Hypogonadotropic).

Classic presentation involves reduced libido, erectile dysfunction, fatigue, and regression of secondary sexual characteristics. However, the clinical picture is highly variable depending on the age of onset (Pre-pubertal vs Post-pubertal). Key diagnostic criteria require two separate early morning (8-10 am) fasting testosterone levels below the reference range, combined with unequivocal signs or symptoms. Management involves identifying reversible causes (e.g., obesity, opioids) before considering lifelong Testosterone Replacement Therapy (TRT). Special consideration is required for fertility, as exogenous testosterone acts as a contraceptive by suppressing spermatogenesis. [1,2,3]

Key Facts

Clinical Pearls

"Treat the Man, Not the Number": Never treat an isolated low testosterone result without clinical symptoms. We treat the syndrome, not the biochemical value.

"Fat is Estrogenic": Adipose tissue contains aromatase, which converts Testosterone to Estradiol. This suppresses the HPG axis (Secondary Hypogonadism). Weight loss can reverse this ("The best testosterone booster is a treadmill").

"The Contraceptive Paradox": Giving testosterone makes men infertile. It suppresses LH/FSH, shutting down sperm production. Do NOT give TRT to men wanting to conceive. Use hCG or Clomifene instead.

"Morning Matters": Testosterone follows a Circadian Rhythm. It peaks at 8am and troughs at 8pm. An afternoon sample in a young man is clinically useless (often 40% lower) and leads to misdiagnosis.

"The Brain vs The Balls":

• Primary (Balls): The brain is shouting (High LH) but the testes can't hear.
• Secondary (Brain): The testes are waiting, but the brain is silent (Low LH).

"Klinefelter's is Stealthy": 1 in 600 men. Often undiagnosed until fertility clinic. Small, firm ("pea-sized") testes are the hallmark.

"The Opioid Trap": Chronic opioids suppress GnRH. "Opioid-Induced Androgen Deficiency" (OPIAD) affects > 50% of chronic users.

"Don't forget the Bones": Hypogonadism is a leading cause of secondary osteoporosis in men. Always consider a DEXA scan.

"Anabolic Steroids": Former abuse causes prolonged hypogonadism ("ASIH"). Testicles may shrink and take months/years to recover.

"Prolactin Priority": Any Secondary Hypogonadism needs a Prolactin level. A prolactinoma is a "do not miss" diagnosis.

Why This Matters Clinically

Male hypogonadism is not just about libido. It is a multi-system disorder associated with increased mortality, primarily from cardiovascular disease. It causes metabolic dysregulation (Diabetes, Metabolic Syndrome), skeletal fragility (Osteoporosis), and profound psychological distress (Depression, Fatigue). Conversely, inappropriate prescribing of TRT is a growing epidemic ("T-Clinics"). Clinicians must skillfully differentiate between true pathological hypogonadism and functional decline due to lifestyle factors (obesity, stress, sleep), protecting patients from the risks of lifelong therapy (Erythrocytosis, Infertility) when lifestyle modification would be safer and more effective.

Historical Context

Historically termed "Andropause" (a misnomer, as cessation is not abrupt like menopause), the field has evolved from gland grafting in the 1920s to modern transdermal and injectable esters. The 2000s saw a surge in "Low T" marketing, necessitating stricter guidelines (Endocrine Society 2018) to prevent over-medicalisation of normal ageing.

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2. Epidemiology

Incidence & Prevalence

Risk Factors

1. Ageing: T levels decline by 1-2% per year after age 40.
2. Obesity: The strongest modifiable risk factor.
3. Comorbidities: T2DM, COPD, OSA (Obstructive Sleep Apnea).
4. Medications: Opioids, Steroids, Chemotherapy, Antipsychotics (Hyperprolactinemia).
5. Genetics: Family history of delayed puberty.

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3. Pathophysiology: Deep Dive

1. The Hypothalamic-Pituitary-Gonadal (HPG) Axis

The HPG axis is a tightly regulated feedback loop that maintains eugonadal status.

1. Hypothalamus: The "Master Clock".
   • Secretes GnRH (Gonadotropin-Releasing Hormone) in a pulsatile fashion (every 90-120 mins).
   • Clinical Relevance: Continuous GnRH (like Goserelin implants) downregulates receptors, causing "chemical castration". Pulsatility is essential for function.
2. Pituitary (Anterior): The "Relay Station".
   • LH (Luteinizing Hormone): Binds to LH receptors on Leydig cells. It regulates the rate-limiting step of testosterone synthesis (moving cholesterol into mitochondria).
   • FSH (Follicle Stimulating Hormone): Binds to Sertoli cells to nourish sperm.
3. Testes: The "Factory".
   • Leydig Cells (Interstitial): Produce Testosterone (95% of total).
   • Sertoli Cells (Tubular): Support Spermatogenesis and produce Inhibin B.

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2. Steroidogenesis (Biosynthesis)

Testosterone is synthesized from Cholesterol. The pathway involves multiple enzymatic steps within the mitochondria and smooth endoplasmic reticulum of Leydig cells:

1. Cholesterol -> Pregnenolone (via StAR protein & CYP11A1).
2. Pregnenolone -> Progesterone (via 3β-HSD).
3. Progesterone -> Androstenedione (via CYP17A1).
4. Androstenedione -> Testosterone (via 17β-HSD).

Defects in any of these enzymes (Congenital Adrenal Hyperplasias) can cause hypogonadism.

3. Mechanism of Action (Molecular)

Testosterone is a lipophilic steroid hormone.

1. Transport: It circulates bound to SHBG (60-70%) and Albumin (30%). Only ~2% is "Free" and active.
2. Cell Entry: Free T diffuses across the cell membrane.
3. Conversion: Inside target cells (e.g., prostate, hair follicles), 5α-reductase converts T into DHT (Dihydrotestosterone), which is 5x more potent.
4. Receptor Binding: T or DHT binds to the Androgen Receptor (AR) in the cytoplasm.
5. Genomic Action: The AR-complex moves to the nucleus, dimerizes, and binds to Androgen Response Elements (AREs) on DNA, driving transcription of anabolic genes (muscle growth, erythropoiesis).

4. Metabolism & Excretion

• Aromatisation: In adipose tissue and brain, T is converted to Oestradiol by the CYP19A1 (Aromatase) enzyme. This oestradiol is crucial for bone density and libido.
• Hepatic Clearance: T is metabolized in the liver to 17-ketosteroids and excreted in urine.
• Half-life: Free T has a half-life of only 10-20 minutes, which is why we cannot just inject pure testosterone (it would vanish instantly); we must use esters (Enanthate, Undecanoate) or gels to prolong action.

5. Why the Axis Fails

• Primary Failure: The Leydig cells are destroyed (trauma, virus, auto-immunity). The pituitary senses low T and pumps out massive amounts of LH to compensate (Hypergonadotropic).
• Secondary Failure: The GnRH pulse generator in the hypothalamus stops firing (stress, opioids, starvation). The pituitary goes dormant. No LH is released. Leydig cells atrophy from disuse.
• Receptor Resistance: Androgen Insensitivity Syndrome (AIS). The hormone is present, but the receptor is mutated. (XY karyotype, but female phenotype).

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4. Classification & Causes

Primary Hypogonadism (Hypergonadotropic)

Pathology: Testicular Failure (Low T, High LH/FSH)

Secondary Hypogonadism (Hypogonadotropic)

Pathology: Pituitary/Hypothalamic Failure (Low T, Low/Normal LH/FSH)

Combined / Mixed Hypogonadism

• Ageing (LOH): Both testicular function and hypothalamic responsiveness decline.
• Alcohol Excess: Direct toxic effect + Central suppression.
• Systemic Disease: CKD, Liver failure, HIV.

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Genetic Syndromes Causing Hypogonadism

About 1 in 500 men have a genetic cause. Recognition is vital for genetic counselling.

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5. Clinical Presentation & Assessment

Presentation varies dramatically by age of onset.

Pre-Pubertal Onset (Eunuchoidism)

If hypogonadism occurs before puberty, sexual maturation does not occur.

• Micropenis and small testes (less than 2-3ml).
• High Voice (Failure of larynx growth).
• Lack of Body Hair (No beard, axillary, or pubic hair).
• Eunuchoid Proportions: Arm span > Height by > 5cm (Epiphyseal plates don't close).
• Poor Muscle Development.
• Gynecomastia.

Post-Pubertal Onset (Adult)

Regression of previously acquired characteristics is the hallmark.

• Sexual:
  • Loss of Libido (Most specific predictor).
  • Erectile Dysfunction (ED): Often loss of nocturnal (sleep-related) erections first. Spontaneous daytime erections decrease.
  • Delayed Ejaculation or reduced ejaculate volume.
  • Infertility (Azoospermia).
• Physical:
  • Decreased need for shaving (Slow beard growth - often unnoticed for months).
  • Gynecomastia (Breast tenderness/growth).
  • Testicular Atrophy (Soft, small testes).
  • Hot Flushes (Acute severe deficiency, e.g., post-orchidectomy).
  • Central Adiposity (Visceral fat accumulation).
• Psychological:
  • Fatigue / Lethargy ("Tired all the time").
  • Depression / Irritability.
  • "Brain Fog" / Poor concentration.
  • Sleep Disturbance.

Detailed Psychosexual History Framework

1. Libido: "How is your desire for sex? Do you think about it?" (Hypogonadal men often have zero interest).
2. Morning Wood: "Do you wake up with an erection?" (A robust morning erection suggests intact nocturnal testosterone surge and vascular supply).
3. Performance: "Can you get and keep an erection?" (ED is often vascular/diabetes, but low libido + ED suggests hormonal).
4. Relationship: "Is relationship stress causing the lack of interest?"

Validated Screening Tools

While biochemical testing is the gold standard, questionnaires can quantify symptom burden.

1. The ADAM Questionnaire (Androgen Deficiency in the Aging Male) Sensitivity: High (97%); Specificity: Low (30%). Good for ruling OUT.

• 1. Decrease in libido?
• 2. Lack of energy?
• 3. Decrease in strength/endurance?
• 4. Lost height?
• 5. Decreased enjoyment of life?
• 6. Sad/Grumpy?
• 7. Erections less strong?
• 8. Deterioration in sports ability?
• 9. Falling asleep after dinner?
• 10. Decreased work performance? Positive result: Yes to Q1 or Q7, OR any 3 other questions.

2. IIEF-5 (International Index of Erectile Function)

• Focuses purely on erectile mechanics. Validated for ED severity but less specific for hypogonadism.

3. AMS (Aging Males' Symptoms) Scale

• A more comprehensive quality-of-life tool measuring somatic, psychological, and sexual dimensions.

Physical Examination Checklist

6. Investigations

Diagnostic Principle

[!IMPORTANT] The Golden Rules of Testing:

1. Morning Only: Samples must be taken between 08:00 and 10:00 AM (or within 3 hours of waking for shift workers).
2. Fasting: Food (especially glucose) suppresses testosterone by up to 30% for 2-4 hours.
3. Repeat: Diagnostic confirmation requires two low levels at least 4 weeks apart.
4. Well State: Do not test during acute illness (fever, trauma, surgery) as T levels drop transiently ("Sick Euthyroid" equivalent).

Diagnostic Algorithm

Step 1: Screening (First Sample)

• Total Testosterone (Fasting, Morning).
• SHBG & Albumin (To calculate Free T).
• Action: If normal -> Stop. If low/borderline -> Proceed to Step 2.

Step 2: Confirmation (Second Sample)

• Total Testosterone (Repeat).
• LH & FSH (To determine Primary vs Secondary).
• Prolactin (Pituitary screen).
• HbA1c & Lipids (Metabolic screen).
• FBC (Baseline Haematocrit).
• PSA (Baseline Prostate check if > 40y).

Step 3: Cause-Specific Testing

• If LH/FSH High -> Primary Failure (Karyotype, Iron Studies).
• If LH/FSH Low -> Secondary Failure (MRI Pituitary, Iron Studies).

Interpreting Testosterone Levels

Interpreting Gonadotropins (LH/FSH): Advanced Diagnostic Framework

The combination of testosterone and gonadotropin levels provides the diagnostic roadmap. Understanding these patterns is critical for identifying the underlying pathology and directing further investigations.

| LH / FSH | Testosterone | Diagnosis | Next Step | |----------|--------------|-----------|-----------|| | HIGH | LOW | Primary Hypogonadism | Karyotype (XXY?), Scrotal US. | | LOW / NORMAL | LOW | Secondary Hypogonadism | Prolactin, MRI Pituitary, Iron Studies. | | HIGH | NORMAL | Compensated Failure | Monitor. Leydig cells struggling but coping. | | LOW | HIGH | Exogenous Androgens | Patient is taking Steroids/Testosterone. |

The Pathophysiology Behind LH/FSH Patterns

Primary Hypogonadism (Hypergonadotropic): The testes fail to produce testosterone despite adequate pituitary stimulation. The hypothalamic-pituitary axis remains intact and responds appropriately to low testosterone by increasing LH and FSH secretion through loss of negative feedback. LH levels can reach 3-10 times the upper limit of normal in severe testicular failure. FSH elevation is particularly pronounced when spermatogenesis is impaired, as inhibin B (produced by Sertoli cells) normally suppresses FSH. [4,5]

Key Distinguishing Features:

• LH typically > 12 IU/L (normal 1.5-9.3 IU/L)
• FSH typically > 12 IU/L (normal 1.4-18.1 IU/L)
• Testosterone less than 8 nmol/L (less than 230 ng/dL)
• Testicular volume often reduced (less than 15 mL)

Secondary Hypogonadism (Hypogonadotropic): The defect lies in the hypothalamus or pituitary gland, resulting in inadequate gonadotropin secretion. The testes remain functionally capable but unstimulated. LH and FSH levels are inappropriately normal or low in the context of low testosterone. Unlike primary failure, the axis can potentially be reactivated with appropriate hormonal stimulation (hCG, pulsatile GnRH). [6,7]

Key Distinguishing Features:

• LH less than 1.5 IU/L or "low-normal" (3-6 IU/L) despite low T
• FSH similarly suppressed or low-normal
• Testicular volume may be normal or slightly reduced
• Sperm count variable (often oligospermia rather than azoospermia)

Diagnostic Pitfalls:

• Obesity-related hypogonadism: Often shows low-normal LH (2-4 IU/L) despite low testosterone due to increased aromatization and leptin-mediated GnRH suppression
• Aging: Gradual rise in LH with declining testosterone represents compensated primary failure
• Mixed patterns: Chronic systemic illness can cause both testicular damage and hypothalamic suppression [8]

Free Testosterone Calculation

Total testosterone can be misleading if SHBG is abnormal.

• High SHBG (Ageing, Hyperthyroid, HIV): Total T is normal, but Free T is low (Symptomatic).
• Low SHBG (Obesity, Hypothyroid, T2DM): Total T is low, but Free T is normal (Asymptomatic).
• Calculator: Use the Vermeulen formula (Requires Total T, SHBG, Albumin).
• Threshold: Free T less than 0.225 nmol/L (or less than 6.5 ng/dL) supports diagnosis.

Additional Investigations

1. Imaging:

• MRI Pituitary:
  • Indication: Secondary Hypogonadism (Low LH) if T less than 5.2 nmol/L OR Prolactin elevated.
  • Goal: Exclude Prolactinoma, Craniopharyngioma, Empty Sella.
• Scrotal Ultrasound:
  • Indication: Testicular mass, cryptorchidism history, microlithiasis.
  • Goal: Exclude tumour (Seminoma).
• DEXA Bone Scan:
  • Indication: All men with confirmed hypogonadism.
  • Goal: Baseline bone density (Osteoporosis risk).

2. Genetic Testing:

• Karyotype:
  • Indication: Primary Hypogonadism (High FSH), small testes (less than 4ml).
  • Goal: Diagnosis of Klinefelter's (47,XXY).
• Iron Studies:
  • Indication: Primary or Secondary.
  • Goal: Haemochromatosis (Bronze Diabetes).

3. Semen Analysis:

• Indication: Fertility often the primary goal.
• Finding: Azoospermia (Klinefelter's/Primary) or Oligospermia.

The "Symptom Specificity" Problem

Symptoms of low T are non-specific (fatigue, depression, weight gain).

• Specific Symptoms (Strong predictors): Loss of morning erections, low libido, shrinkage of testes.
• Non-Specific Symptoms (Weak predictors): Fatigue, poor concentration, sleep disturbance. Diagnosis hinges on biochemical confirmation, not just symptoms.

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7. Lifestyle Integration & Reversible Factors

Before reaching for the prescription pad, all reversible causes of functional hypogonadism must be aggressively managed.

1. The Obesity-Hypogonadism Cycle (MOSH)

Male Obesity-Secondary Hypogonadism (MOSH) is the most common cause of low T in the modern world.

• Mechanism:
  1. Aromatisation: Visceral fat contains high levels of Aromatase, converting T into Oestradiol. Oestradiol suppresses the pituitary (Low LH).
  2. Inflammation: Adipocytes release pro-inflammatory cytokines (TNF-α, IL-6) which directly inhibit Leydig cell function.
  3. Insulin Resistance: Lowers SHBG, reducing total T.
• Intervention: Weight loss of > 10% can restore T levels to the normal range without drugs.
• Quote for Patients: "The best testosterone booster is a treadmill, not a pill."

2. Sleep Architecture

Testosterone production is sleep-dependent.

• Physiology: The major pulse of GnRH/LH occurs during REM sleep.
• Chronotype: Shift workers and those with fragmented sleep (e.g., Obstructive Sleep Apnea) lose this nocturnal surge.
• Evidence: Restricting sleep to 5 hours/night for 1 week lowers T levels by 15% (to levels seen in men 10-15 years older).
• Action: Screen for OSA (Snoring, choking, daytime sleepiness) - CPAP can improve T levels.

3. Exercise Protocol

Not all exercise is equal for hormones.

• Resistance Training (Weights): Acute upregulation of androgen receptors and T release. Best for T optimization.
• HIIT: Moderate boost.
• Chronic Endurance (Ultra-running): Creates a catabolic cortisol-dominant state that lowers T ("Exercise Hypogonadal Male Condition").
• Prescription: 3-4 sessions of compound lifting (Squats, Deadlifts) per week.

4. Nutritional Support

Supplements are rampant in this space, but few have evidence.

• Zinc: Essential co-factor for steroidogenesis. Supplementation only helps if zinc deficient (common in vegetarians).
• Vitamin D: Leydig cells have Vit D receptors. Correction of deficiency normalises T.
• Magnesium: Increases bioavailability of T by displacing it from SHBG.
• Alcohol: Ethanol is a direct testicular toxin. Chronic intake (> 14 units/week) lowers T and increases Oestradiol.

4. Nutritional Support: The "Testosterone Diet"

Scientific consensus supports specific micronutrients for Leydig cell function.

Foods to Avoid (The "Estrogenic" Diet)

5. Stress Management (Cortisol Steal)

• Physiology: The "Pregnenolone Steal". During chronic stress, cholesterol is diverted to produce Cortisol (survival) instead of Testosterone (reproduction).
• Clinical: High stress = Low Libido. Mindfulness and stress reduction are valid medical interventions here.

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8. Management

Key Principles

[!NOTE] Treatment Goals:

1. Restore physiological testosterone levels (mid-normal range).
2. Alleviate symptoms (Libido, Energy, Mood).
3. Prevent long-term sequelae (Osteoporosis, Metabolic Syndrome).

The "Reversible First" Rule: Always correct obesity, treat sleep apnea, and stop offending medications (opioids) before starting lifelong TRT.

Management Algorithm

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1. Lifestyle Modification (First-Line)

• Weight Loss: Adiposity increases aromatase activity. Losing 10% body weight can raise T by 2-3 nmol/L.
• Sleep Hygiene: Sleep deprivation crashes T levels. Aim for 7-8 hours.
• Resistance Training: Acute boost in T levels.

2. Is Fertility Desired?

• YES: STOP. Do NOT prescribe Testosterone.
  • Refer to Reproductive Endocrinology.
  • Consider hCG (Human Chorionic Gonadotropin) or Clomifene (SERM) to stimulate endogenous production.
• NO: Proceed to Testosterone Replacement Therapy (TRT).

Testosterone Replacement Therapy (TRT) Options: Evidence-Based Formulation Guide

We replace bioidentical testosterone. The choice depends on patient preference, pharmacokinetic profile, cost, and desired steady-state requirements. Modern formulations aim to replicate physiological testosterone patterns while minimizing adverse effects.

Comparative Pharmacokinetics

Transdermal Gel (1% formulation):

• Time to steady state: 2-3 days
• Tmax (peak): 4-6 hours post-application
• Maintains testosterone within physiological range (10-30 nmol/L)
• Dihydrotestosterone (DHT) elevation: Moderate (150-200% of baseline)
• Aromatization to estradiol: Physiological
• Inter-patient variability: High (absorption ranges 9-14% of applied dose)

Testosterone Undecanoate Injection (Nebido):

• Loading phase: 0, 6, 18 weeks, then 12-weekly
• Time to steady state: 33-40 weeks (7-9 months)
• Half-life: 33.9 days (longest ester)
• Maintains trough levels > 12 nmol/L in 85% of patients
• Requires castor oil vehicle (risk of pulmonary oil microembolism - rare)

Testosterone Enanthate/Cypionate:

• Half-life: 4.5 days (Enanthate), 8 days (Cypionate)
• Cmax occurs 24-48h post-injection (often supra-physiological 40-70 nmol/L)
• Trough at day 10-14 (often sub-therapeutic 8-12 nmol/L)
• Micro-dosing protocol (50-100mg twice weekly) improves stability

Key Clinical Insight: The ester length determines lipophilicity and depot duration. Testosterone is esterified at the 17β-hydroxyl position with carboxylic acids:

• Propionate (3 carbons): Half-life 0.8 days
• Enanthate (7 carbons): Half-life 4.5 days
• Cypionate (8 carbons): Half-life 8 days
• Undecanoate (11 carbons): Half-life 33.9 days

After intramuscular injection, the ester is slowly hydrolyzed by tissue esterases to release free testosterone. Longer esters create larger oil depots with slower hydrolysis rates. [17,18]

Pharmacology of Esters: Deep Dive

Testosterone itself has a half-life of 10 minutes. To make it usable, we modify the molecule at the 17-beta hydroxyl group.

1. Esterification:

• We attach an "ester chain" (Carbon backbone).
• Rule: The longer the carbon chain, the more lipophilic (fat-soluble) the molecule becomes, and the slower it releases from the muscle depot.

2. Pharmacokinetics of Common Esters:

3. "The Rollercoaster Effect":

• With short esters (Enanthate/Sustanon) given infrequently (e.g., every 3-4 weeks), patients experience supra-physiological peaks (Aggression, Acne) followed by sub-therapeutic troughs (Fatigue).
• Solution: More frequent, smaller doses (Micro-dosing) mimics natural physiology better.

Monitoring Protocol (Mandatory)

TRT is not "fire and forget". Strict monitoring is required for safety.

Managing Complications

1. Erythrocytosis (Polycythemia)

• Mechanism: T stimulates Erythropoietin (EPO).
• Risk: Stroke, Thrombosis.
• Threshold: Haematocrit (Hct) > 0.54.
• Action:
  1. Check hydration / Smoking (Stop smoking).
  2. Reduce Testosterone dose.
  3. Switch from Injection to Gel (Less peaks).
  4. Venesection: Remove 450ml blood.
  5. Stop TRT if persistent.

2. Prostate Safety

• Facts: TRT does not cause prostate cancer, but can stimulate growth of existing occult cancer.
• Action: Monitor PSA.
• Urgent Urology Referral:
  • PSA > 4.0 ng/mL.
  • Rise in PSA > 1.4 ng/mL in 1 year.
  • Abnormal DRE (nodule).
• BPH: Can worsen Luts (Lower urinary tract symptoms).

3. Infertility

• Mechanism: Negative feedback suppresses LH/FSH -> Intra-testicular testosterone drops -> Spermatogenesis stops (Azoospermia).
• Reversibility: Usually reversible, but can take 6-12 months after stopping TRT.
• Action: Never start TRT if pregnancy planned in next 12 months.

Fertility Induction (Specialist): Preserving and Restoring Spermatogenesis

For hypogonadal men wanting to achieve biological fatherhood, testosterone replacement is contraindicated. The challenge is to stimulate endogenous testosterone production AND maintain intratesticular testosterone at levels 50-100 times higher than serum concentrations - the threshold required for spermatogenesis. Three evidence-based strategies exist:

1. Human Chorionic Gonadotropin (hCG) Monotherapy

Mechanism: hCG is structurally homologous to LH and binds LH receptors on Leydig cells with identical affinity. It stimulates endogenous testosterone production without suppressing the HPG axis. The longer half-life of hCG (24-36 hours) compared to LH (20 minutes) allows practical dosing schedules. [19,20]

Protocol:

• Dose: 1500-3000 IU subcutaneous, 2-3 times per week (Monday/Thursday or Monday/Wednesday/Friday)
• Alternative: 5000 IU intramuscular weekly (less preferred due to peaks)
• Duration: Minimum 3-6 months to see spermatogenesis
• Monitoring: Testosterone (maintain 15-25 nmol/L), semen analysis every 3 months

Evidence Base:

• Sperm production success: 60-90% in secondary hypogonadism [21]
• Mean time to first sperm appearance: 4-6 months
• Pregnancy rates: 40-60% within 12-18 months of treatment [22]
• Prior TRT duration inversely correlates with success (> 24 months TRT reduces success to 50%)

Advantages:

• Monotherapy (no need for FSH in most secondary hypogonadism cases)
• Maintains testicular volume
• Restores libido and energy
• Can be used indefinitely

Disadvantages:

• Cost: £100-200/month (more expensive than TRT)
• Injection requirement
• Gynecomastia risk (15-25% due to increased aromatization)
• Variable response (poor in primary hypogonadism)

2. Selective Estrogen Receptor Modulators (SERMs): Clomiphene Citrate

Mechanism: Clomiphene blocks estrogen receptors in the hypothalamus and pituitary, eliminating negative feedback from estradiol. This "tricks" the brain into perceiving low estrogen, prompting increased GnRH and gonadotropin (LH/FSH) secretion. The resulting endogenous LH/FSH stimulation increases both testosterone production and spermatogenesis. [23,24]

Protocol:

• Dose: 25-50mg oral daily (or alternate days for maintenance)
• Initiation: Start low (12.5-25mg) and titrate based on testosterone response
• Target: Raise testosterone to mid-normal range (15-25 nmol/L)
• Monitoring: Testosterone and LH/FSH at 4-6 weeks, then 3-monthly

Evidence Base:

• Testosterone increase: 50-100% from baseline (typically 8→16 nmol/L) [25]
• Sperm concentration improvement: Demonstrated in idiopathic oligospermia
• Pregnancy rates: 30-40% in couples (meta-analysis) [26]
• Off-label use in men (licensed for female ovulation induction)

Advantages:

• Oral administration (better compliance than injections)
• Cheap (£15-30/month)
• Maintains testicular size
• Raises both T and sperm simultaneously
• Can be used long-term (years)

Disadvantages:

• Variable response (20-30% non-responders)
• Visual disturbances (2-5%): Blurred vision, photophobia (reversible)
• Emotional lability, mood swings (10-15%)
• Estrogenic effects: Gynecomastia possible but less than hCG
• Not effective in primary hypogonadism (testes cannot respond)
• Theoretical concern about long-term estrogen receptor blockade effects

Special Consideration - Enclomiphene: Clomiphene is a racemic mixture of two isomers:

• Zuclomiphene (38%): Long half-life (weeks), weak estrogen agonist activity
• Enclomiphene (62%): Shorter half-life (days), pure estrogen antagonist

Isolated enclomiphene may offer better efficacy and fewer side effects, but is not widely available. [27]

3. Combined hCG + recombinant FSH (rFSH)

Indication: Reserved for cases where hCG alone fails to induce spermatogenesis after 6-9 months, or in severe FSH deficiency (e.g., Kallmann syndrome, hypopituitarism).

Mechanism: FSH directly stimulates Sertoli cells, which provide the structural support and nutrition for developing spermatocytes. In congenital hypogonadotropic hypogonadism, lifelong absence of FSH causes Sertoli cell immaturity. Adding FSH to hCG therapy completes the hormonal milieu required for spermatogenesis. [28]

Protocol:

• hCG: 1500-3000 IU SC 2-3x weekly (as above)
• rFSH: 75-150 IU SC 3x weekly (Gonal-F, Puregon)
• Duration: 12-24 months often required
• Monitoring: Semen analysis every 3 months, inhibin B as marker of Sertoli cell function

Evidence Base:

• Success rate in congenital hypogonadotropic hypogonadism: 70-90% [29]
• Mean time to spermatogenesis: 9-18 months
• Sperm concentrations: Often sufficient for IVF/ICSI (> 1 million/mL), natural conception less reliable
• Testicular volume increases significantly (biomarker of success)

Advantages:

• Effective even in complete GnRH deficiency
• Predictable response with adequate time

Disadvantages:

• Very expensive (£500-1000/month)
• Dual injections required
• Long treatment duration
• Specialist-only therapy (reproductive endocrinology/andrology)

Fertility Preservation Before TRT: Sperm Cryopreservation

Indication: ALL men with hypogonadism considering TRT who have any future fertility desires should be offered sperm banking before starting therapy. [30,31]

Rationale:

• TRT-induced azoospermia is usually reversible, but recovery is unpredictable
• 10-15% of men fail to recover spermatogenesis even after 12-24 months off TRT
• Prior testicular insult (chemotherapy, torsion, cryptorchidism) reduces recovery probability
• Age > 40 at TRT initiation associated with poorer recovery

Process:

1. Baseline semen analysis (may already show oligospermia/azoospermia in hypogonadism)
2. If sperm present: Cryopreserve 2-3 samples (1 week apart)
3. If azoospermia: Consider fertility induction first (3-6 months hCG/Clomiphene) then bank
4. If persistent azoospermia: Testicular sperm extraction (TESE) for cryopreservation

Cost: £300-800 setup + £150-300/year storage (UK/Australia)

Recovery of Spermatogenesis After TRT: The "Post-TRT Protocol"

Clinical Scenario: Patient on TRT now desires pregnancy. What is the recovery strategy?

Timeline:

• Stop TRT immediately
• Expect testosterone to nadir within 2-4 weeks (symptomatic period)
• Spermatogenesis cycle: 74 days minimum (requires 3+ months even in optimal conditions)
• Realistic expectation: 6-12 months to sperm recovery
• 15-25% may take > 18 months or fail to recover

Recovery Protocol (Evidence-Based):

Option A: Conservative "Wait and Monitor"

• Stop TRT and allow natural axis recovery
• Monthly semen analysis
• Suitable if: Short TRT duration (less than 12 months), young age (less than 35), normal baseline fertility

Option B: Aggressive "Kickstart" (Preferred)

• hCG: 2000-3000 IU SC 3x weekly immediately upon TRT cessation
• Continue for 3 months minimum
• Add Clomiphene 25-50mg daily if no response at 3 months
• Add rFSH if still no sperm at 6-9 months

Evidence: Meta-analysis of TRT discontinuation studies shows hCG-based recovery protocols achieve sperm appearance in 67-90% of patients vs. 50-60% spontaneous recovery, with faster time to conception (median 7 months vs. 14 months). [32,33]

Key Counseling Points:

• Sperm quality may remain suboptimal (reduced motility, morphology)
• Assisted reproduction (IUI/IVF/ICSI) may still be required in 30-40%
• Partner should undergo fertility assessment concurrently
• Decision to permanently abandon TRT should be considered if pregnancy is priority

Contraindications to TRT

Absolute:

• Prostate Cancer (Active or metastatic).
• Male Breast Cancer.
• Active desire for fertility (in next 12 months).
• Haematocrit > 54%.
• Severe unsafe Heart Failure (Uncontrolled).

Relative:

• Severe Sleep Apnea (Untreated) - T can worsen it.
• Severe LUTS (IPSS score > 19).

Emerging Therapies and Future Directions

1. Oral Testosterone Undecanoate (Jatenzo, Kyzatrex) Recently approved oral formulations absorbed via the lymphatic system, bypassing first-pass hepatic metabolism. Advantages include twice-daily dosing, rapid reversibility, and avoidance of skin transfer risk. Limited long-term safety data but represents an alternative for patients refusing injections or gels. [45]

2. Subcutaneous Testosterone (Xyosted) Weekly auto-injector delivering testosterone enanthate subcutaneously. Improved pharmacokinetics compared to intramuscular injection with smaller injection volume (0.5ml vs 1-4ml) and reduced pain. Maintains steady-state levels within physiological range. [46]

3. Kisspeptin Agonists Novel investigational therapy targeting the upstream regulator of GnRH secretion. Kisspeptin-10 administration stimulates endogenous LH/FSH pulsatility, potentially offering fertility-preserving testosterone augmentation in secondary hypogonadism. Currently in Phase II trials for hypogonadotropic hypogonadism. [47]

4. Selective Androgen Receptor Modulators (SARMs) Tissue-selective androgen receptor ligands designed to provide anabolic benefits (muscle, bone) while minimizing androgenic side effects (prostate, hair loss). Multiple compounds under investigation but none yet approved due to safety concerns. Not recommended outside clinical trials. [48]

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8. Complications of Untreated Disease

Hypogonadism is not merely a quality-of-life issue. Long-term androgen deficiency has profound systemic consequences.

1. Metabolic Syndrome & Diabetes

• Mechanism: Testosterone increases expression of glucose transporters (GLUT4) and mitochondrial function.
• Impact: Low T is an independent risk factor for Insulin Resistance and Type 2 Diabetes.
• Vicious Cycle: Obesity -> Low T -> Fatigue/Muscle Loss -> More Obesity.
• Evidence: Men with low T have a 2x risk of developing T2DM over 10 years.

2. Osteoporosis & Fragility

• Mechanism: Testosterone is converted to Oestradiol in bone, which inhibits osteoclasts (bone resorption).
• Impact: 20% of men with vertebral fractures have untreated hypogonadism.
• Guideline: All men with low T should have a DEXA scan.
• Treatment: TRT increases bone density, but bisphosphonates may still be needed for established osteoporosis.

3. Anaemia

• Mechanism: T stimulates Erythropoietin (EPO) secretion and suppresses Hepcidin (allowing better iron utilisation).
• Impact: "Unexplained anaemia" in older men is often due to hypogonadism. Hb typically rises by 10-20 g/L with TRT.

4. Cardiovascular Disease: The Evidence Revolution

The relationship between testosterone and cardiovascular health has been one of the most contentious areas in endocrinology. Early observational data suggested increased CV risk with TRT, but definitive RCT evidence has reshaped clinical practice.

The Paradigox: Untreated Hypogonadism Increases CV Mortality

Epidemiological studies consistently demonstrate that low endogenous testosterone is an independent risk factor for cardiovascular disease and all-cause mortality. [34,35,36]

Evidence:

• Men with testosterone less than 8.7 nmol/L have 2-fold higher all-cause mortality over 20 years compared to eugonadal men (Framingham Heart Study) [37]
• Each 6 nmol/L decrease in testosterone associated with 30% increased risk of death (meta-analysis n=12,000) [38]
• Low testosterone predicts incident heart failure (HR 1.8, 95% CI 1.3-2.5) independent of traditional risk factors [39]

Mechanisms Linking Low Testosterone to CV Risk:

1. Metabolic Dysfunction:
   • Increased visceral adiposity and insulin resistance
   • Dyslipidemia (decreased HDL, increased triglycerides, small dense LDL)
   • Pro-inflammatory state (elevated CRP, IL-6, TNF-α)
2. Vascular Dysfunction:
   • Endothelial dysfunction (reduced nitric oxide bioavailability)
   • Increased arterial stiffness
   • Accelerated atherosclerosis
3. Cardiac Effects:
   • Reduced cardiac contractility
   • Increased QT interval variability
   • Pro-arrhythmic substrate

The TRAVERSE Trial: Definitive Safety Evidence (2023)

Design: Largest RCT of TRT cardiovascular safety

• Population: 5,246 men aged 45-80 with hypogonadism AND pre-existing/high risk cardiovascular disease
• Intervention: Transdermal testosterone gel (target 13-30 nmol/L) vs. placebo
• Duration: Median 33 months follow-up
• Primary outcome: Major Adverse Cardiovascular Events (MACE) - composite of non-fatal MI, non-fatal stroke, or CV death [40]

Results:

• MACE occurred in 7.0% of testosterone group vs. 7.3% of placebo (HR 0.96, 95% CI 0.78-1.17, p=0.65)
• Non-inferiority demonstrated: TRT does not increase cardiovascular risk
• Secondary findings:
  • "Atrial fibrillation: Modestly increased (5.2% vs. 3.3%, HR 1.54)"
  • "Venous thromboembolism: Numerically higher but not statistically significant (0.9% vs. 0.5%)"
  • "All-cause mortality: Similar (3.3% vs. 3.7%)"

Clinical Implications:

• TRT is safe in men with cardiovascular disease when appropriately dosed
• Target mid-normal testosterone range (not supra-physiological)
• Monitor for AF, particularly in elderly and those with existing cardiac disease
• Haematocrit monitoring remains essential (VTE risk related to erythrocytosis)

Limitations:

• Excluded men with Hct > 50%, recent MI (less than 6 months), NYHA Class IV heart failure
• Transdermal gel only (not generalizable to high-dose injections)
• Predominantly white population

Other Major Cardiovascular Trials:

T-Trials (2016): Seven coordinated RCTs (n=790) in older men ≥65 years

• Outcomes: No increase in coronary artery calcium progression [41]
• Atherosclerosis: No acceleration of subclinical atherosclerosis
• Blood pressure: Small increase in SBP (+3 mmHg, not clinically significant)

TOM Trial (2010): The cautionary tale

• Population: Frail elderly men (mean age 74) with mobility limitation
• Intervention: High-dose testosterone gel (10g daily, achieving 21 nmol/L)
• Stopped early due to increased cardiovascular events (23 vs. 5 events)
• Critique: Excessive dosing in high-risk population, small sample, baseline imbalances [42]

Current Consensus (2024):

• TRT does NOT cause cardiovascular disease in appropriately selected patients
• May be cardioprotective by improving metabolic risk factors
• Dose matters: Target physiological replacement, not supraphysiological enhancement
• Monitoring haematocrit is critical to minimize VTE/stroke risk [43,44]

5. Neuropsychiatric

• Cognition: T receptors are dense in the hippocampus. Low T is linked to "Brain Fog" and slower processing speed, though dementia links are unproven.
• Mood: Dysthymia and irritability ("Grumpy Old Man" syndrome) are classic features.

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9. Drug Interactions & Secondary Causes

Before diagnosing "Idiopathic", review the drug chart.

Drugs that Lower Testosterone (Central Suppression)

These drugs suppress GnRH or LH/FSH (Secondary Hypogonadism).

Drugs that Lower Testosterone (Testicular Toxicity)

These drugs damage the Leydig cells directly (Primary Hypogonadism).

Drugs that Block Action (Androgen Resistance)

Testosterone levels may be High, but it can't work.

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10. Complex Clinical Case Studies

Case 1: The "Tired Executive" (Functional vs Organic)

Presentation: A 52-year-old CEO presents with fatigue, loss of libido, and weight gain. BMI 34. He drinks 30 units of alcohol/week. Labs:

• Testosterone (09:00): 9.2 nmol/L (Borderline)
• LH: 3.1 IU/L (Normal)
• SHBG: 20 nmol/L (Low)

Analysis: This is Functional Hypogonadism (Secondary to Obesity/Alcohol).

• Low SHBG (due to obesity) means Free Testosterone might be normal despite low Total T.
• The LH is not elevated, so the testes are fine. The brain is just "dampened".

Management:

• Do NOT start TRT. It will suppress his own sperm/T production and ignore the root cause.
• Plan: Alcohol reduction + Weight loss.
• Outcome: After losing 8kg and cutting alcohol, T rose to 14.5 nmol/L. Symptoms resolved.

Case 2: The Fertility Dilemma (Klinefelter's)

Presentation: A 28-year-old man presents with infertility (trying for 2 years). He is tall (192cm) and has noticed reduced shaving. Examination:

• Small, firm testes (3ml).
• Gynecomastia. Labs:
• Testosterone: 6.0 nmol/L (Low)
• LH: 22 IU/L (High) -> Primary Failure.
• FSH: 35 IU/L (High) -> Spermatogenic Failure.

Diagnosis: Klinefelter's Syndrome (47,XXY). Confirmed by Karyotype.

Management:

• Fertility: The high FSH suggests the testes are failing to produce sperm. Natural conception is unlikely.
• Action: Urgent referral for Micro-TESE (surgical sperm retrieval) before starting TRT.
• Once sperm issue addressed (or abandoned), start lifelong TRT for bone/heart health.

Case 3: The "Gym Goer" (ASIH)

Presentation: A 25-year-old amateur bodybuilder complains of "crashing" fatigue and zero libido. He stopped his "cycle" of Trenbolone 4 weeks ago. Labs:

• Testosterone: 2.1 nmol/L (Very Low)
• LH: less than 0.1 IU/L (Suppressed)
• FSH: less than 0.1 IU/L (Suppressed)

Analysis: Anabolic Steroid Induced Hypogonadism (ASIH). His HPG axis is dormant due to prolonged negative feedback from synthetic androgens.

Management:

• Reassurance: Why does he feel terrible? Because his T is 2.1!
• Choice:
  1. Wait: Can take 6-12 months.
  2. Kickstart: Short course of Clomifene or hCG to wake up the pituitary/testes.
• Warning: Do not give T-Gel, or he will never recover his own production.

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11. Special Perspectives

1. The Ageing Male (Late Onset Hypogonadism)

"Andropause" is controversial. Unlike menopause (ovarian failure), testicular function declines gradually.

• Pathology: Combined Primary (Leydig cell apoptosis) and Secondary (Hypothalamic sensitivity) failure.
• Diagnostic Challenge: SHBG rises with age (1-2% per year), binding more testosterone. Functional suppression from comorbidities (Obesity, Hypertension) is common.
• Treatment Threshold: Higher threshold for treatment. We treat symptoms, not just numbers.
• Safety: Caution with prostate and cardiovascular risk in the > 65s. "Start low, go slow".

2. Cancer Survivors (The "Onco-fertility" Patient)

Young men surviving testicular cancer or lymphoma often face dual challenges: Hypogonadism + Infertility.

• Chemotherapy (Alkylating agents): Causes permanent azoospermia (damage to germ cells) but Leydig cells (Testosterone) are more resistant. However, 20-30% develop hypogonadism years later.
• Radiotherapy: TBI (Total Body Irradiation) or scatter radiation damages Leydig cells.
• Management:
  • Sperm banking prior to treatment is the gold standard.
  • Long-term annual monitoring of T, LH, FSH is mandatory.
  • Bone health is critical (risk of osteopenia in young survivors).

3. HIV Infection

Hypogonadism is highly prevalent (20-50%) in HIV+ men.

• Mechanisms:
  • Primary: Direct viral toxicity to testes.
  • Secondary: Chronic inflammation, opportunistic infections, malnutrition.
  • Iatrogenic: Interaction with antiretrovirals (some increase SHBG).
• Impact: Worsens "HIV Wasting Syndrome" and frailty.
• Treatment: TRT is effective for muscle mass and libido, with similar safety profile to HIV-negative men.

4. Transgender Health (Trans-Masculine)

While "Male Hypogonadism" usually refers to cis-men, the principles of TRT apply to trans-men (AFAB) undergoing transition.

• Goal: Induce virilisation (Beard growth, voice deepening, muscle mass).
• Target Levels: Same as cis-male reference range (10-30 nmol/L).
• Specifics:
  • Monitor Hct closely (polycythemia risk is higher).
  • Vaginal atrophy is a specific side effect.
  • PCOS history may complicate metabolic risk.

5. The "Gym Rat" (Body Dysmorphia)

A growing demographic: young men with normal T seeking "Supra-physiological" levels.

• Muscle Dysmorphia ("Bigorexia"): Pathological belief that one is too small.
• The Trap: Taking steroids shuts down natural production, causing shrinkage of testes. Panic ensues -> Takes more steroids -> Vicious cycle.
• Harm Reduction: If they won't stop, monitor BP, Lipids, Hct. Educate on the difference between TRT (replacement) and AAS (abuse).

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12. Patient Explanation

The "Fuel Tank" Analogy

"Imagine your body is a car and testosterone is the fuel.

• Grade 1 (Normal): The tank is full. The car runs smoothly. Adding more fuel (overflowing the tank) won't make the car go faster, but it might damage the paintwork (side effects).
• Grade 2 (Low): The tank is empty. The car splutters, stalls, and has no power. Filling the tank back to normal restores performance.

Our goal is to get your tank to 'Full', not to 'Overflow'. Taking extra testosterone when your levels are normal is dangerous, but replacing it when it's low is restoring health."

Common Patient Questions (FAQs)

Q: Is this 'Male Menopause'? A: No. Menopause happens to all women and is a rapid shutdown. Low testosterone only happens to some men (about 2-5%) and is usually due to a specific medical issue or weight gain. We call it "Testosterone Deficiency Syndrome".

Q: Will taking testosterone make me aggressive ("Roid Rage")? A: No. "Roid rage" is associated with massive doses used by bodybuilders (10-20 times the medical dose). Therapeutic TRT restores you to normal levels, which usually improves mood and reduces irritability.

Q: Will it shrink my testicles? A: Yes, it is possible. When you take testosterone from the outside, your brain tells your own testicles to "go to sleep" because they aren't needed. They may become smaller and softer. This is reversible if treatment stops, but it can take months.

Q: Can I have children while on treatment? A: No. TRT acts as a powerful contraceptive. It stops sperm production. If you want to have children now or in the near future, we must use different medication (like HCG) instead of testosterone.

Q: Does it cause prostate cancer? A: Current evidence shows TRT does not cause prostate cancer. However, if you have a tiny hidden cancer (which is common in older men), testosterone might make it grow. This is why we monitor your PSA blood test so strictly.

Q: How long do I need to take it? A: Usually for life. TRT is a replacement therapy (like insulin for diabetes), not a cure. If you stop, your levels will drop back to where they started. The exception is if your low testosterone was caused by weight gain – losing weight might allow you to stop.

Myth-Busting

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12. Evidence & Guidelines

Key Guidelines Summary

Landmark Trials & Evidence

1. The TRAVERSE Trial (Lincoff et al., 2023)

• Study Type: Large Multicentre RCT (n=5246).
• Population: Men 45-80y with low T and CV risk/disease.
• Intervention: Transdermal Testosterone Gel vs Placebo.
• Outcome: Major Adverse Cardiac Events (MACE).
• Result: No significant difference in MACE between T-group (7.0%) and Placebo (7.3%).
• Clinical Impact: The definitive safety study. It dispelled the myth that TRT causes heart attacks. However, it confirmed a higher rate of arrhythmias (Atrial Fibrillation) and PE.
• PMID: 37326322 (Link)

2. The T-Trials (Snyder et al., 2016)

• Study Type: Set of 7 coordinated RCTs (n=790).
• Result: TRT moderately improved sexual function and some aspects of mood/depressive symptoms. Minimal effect on vitality/walking distance.
• Implication: TRT is great for sex, good for mood, but not a miracle cure for fatigue.
• PMID: 26886521

3. Bone Density Studies (Ebeling et al., 2022)

• Finding: TRT significantly increases volumetric bone density and estimated bone strength in hypogonadal men.
• Implication: Essential for preventing osteoporosis in men.

Evolving Evidence

• Diabetes Reversal: Emerging evidence suggests TRT in hypogonadal men with T2DM improves insulin sensitivity and glycaemic control (T4DM study).
• Prostate Cancer: The "Saturation Model" suggests that once androgen receptors are saturated (at low T levels), adding more T does not increase cancer growth. This is shifting the paradigm on TRT in men with history of treated prostate cancer (under strict specialist supervision).

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13. Historical Perspectives: The Quest for Virility

The history of testosterone is the history of humanity's obsession with youth and strength.

1. The Rooster Experiment (1849)

Arnold Berthold (Göttingen) performed the first true endocrinology experiment.

• He castrated roosters (capons): They stopped crowing, combs shrank, and they became docile.
• He re-implanted the testes into the abdomen: The roosters regained their crowing, combs, and aggression.
• Conclusion: Testes release a substance into the blood (not nerves) that controls maleness.

2. The Elixir of Life (1889)

Charles-Édouard Brown-Séquard, a 72-year-old neurologist, injected himself with an extract of crushed dog and guinea pig testicles.

• He reported miraculous rejuvenation: "I felt like a young man again."
• Reality: It was the Placebo Effect (and likely a dangerous immune reaction). The amount of T in the extract was negligible. However, it sparked the field of Organotherapy.

3. The Monkey Gland Era (1920s)

Serge Voronoff, a Russian surgeon in Paris, believed that animal testes held the secret to longevity.

• He transplanted thin slices of Chimpanzee and Baboon testicles into the scrotums of wealthy elderly men.
• Thousands of operations were performed worldwide.
• Outcome: Failed. The grafts eventually died or fibrosed. Voronoff was ridiculed, but his principle of hormone replacement was directionally correct.

4. The Miracle Year (1935)

The race to isolate the "Male Hormone" culminated in 1935.

• Karolinska Institute: Isolated 10mg of testosterone from tons of bull testicles.
• Fred Koch (Chicago): Needed 40 tons of bull testes to get 10-20 mg.
• Adolf Butenandt & Leopold Ruzicka: Figured out how to synthesize testosterone from Cholesterol. This made mass production possible.
• Result: They shared the 1939 Nobel Prize in Chemistry.

5. The Golden Age of Steroids (1950s)

• Dr. John Ziegler: Witnessed Russian weightlifters dominating the Olympics using testosterone.
• He worked with Ciba Pharmaceuticals to create Methandrostenolone (Dianabol) - the first anabolic steroid.
• This launched the era of doping in sports and bodybuilding.

6. The "Low T" Marketing Boom (2000s)

• Pharmaceutical companies began marketing "Low T" as a treatable disease for vague symptoms (fatigue).
• Prescriptions for AndroGel skyrocketed 400%.
• Pushback: The FDA and medical societies tightened guidelines (2014-2018) to ensure only men with pathological hypogonadism were treated, not just normal ageing.

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Appendix 2: Legal, Sports, & Regulatory Issues

1. Prescribing Controls

Testosterone is a Controlled Drug in most jurisdictions due to its potential for abuse (Anabolic Steroids).

• UK: Schedule 4 Part 2 (Misuse of Drugs Regulations).
  • Can be possessed for personal use without a prescription (in small quantity).
  • Illegal to supply/sell without a licence.
  • Prescriptions are valid for 28 days only.
• USA: Schedule III Controlled Substance.
  • Strict monitoring of distribution.
  • "Script Mill" clinics are under increasing scrutiny.

2. Driving & Employment

• Driving: There are no specific restrictions for patients on therapeutic TRT. However, abuse leading to aggressive behaviour ("Roid Rage") can lead to licence revocation on psychiatric grounds.
• Employment: Certain professions (Private Military, Aviation) may screen for drugs. A declare prescription prevents failure.

3. Anti-Doping in Sports (WADA)

Testosterone is strictly banned in professional sports.

• The T:E Ratio: Urine testing measures the ratio of Testosterone Glucuronide to Epitestosterone Glucuronide (T:E).
  • Natural Ratio: 1:1.
  • WADA Limit: 4:1.
  • Exogenous testosterone suppresses Epitestosterone, shooting the ratio up (often > 20:1).
• CIR (Carbon Isotope Ratio): The definitive test. Synthetic testosterone (derived from Soy/Yam) has a different Carbon-13 signature than endogenous testosterone. This "fingerprint" proves doping.
• TUE (Therapeutic Use Exemption): Athletes with proven organic hypogonadism (e.g., Anorchism, Pituitary tumour) can apply for a TUE to take TRT. However, TUEs are never granted for "Functional" or "Age-related" low T.

4. The "TRT Clinic" Industry

A multi-billion dollar unregulated grey market exists.

• Red Flags for Patients:
  • Clinics that prescribe based on symptoms alone (ignoring normal bloods).
  • Clinics treating "Low Normal" levels.
  • Compounding pharmacies sending "custom blends".
  • Lack of physical exams (Online only).
• Medical Liability: Physicians prescribing TRT to eugonadal men (for performance/aesthetics) face striking off/loss of licence.

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15. Examination Focus

High-Yield Facts for Exams

1. The Discriminator: Always look at LH/FSH.
   • High LH + Low T = Primary (Testes Problem).
   • Low LH + Low T = Secondary (Brain Problem).
2. Kallmann's Triad: Anosmia (Can't smell) + Hypogonadism + Colour Blindness (sometimes).
3. Klinefelter's (47,XXY): The most common cause of primary hypogonadism. Look for tall stature and gynecomastia.
4. "Fasting Morning Sample": The absolute mantra for diagnosis. Afternoon samples are invalid.
5. TRT and Fertility: "Testosterone is a contraceptive". Do NOT give it to men wanting kids.

Clinical Signs to Look For

Common OSCE Stations

Station 1: History Taking (The "Tired Man")

• Scenario: 45yo man, tired, lost libido.
• Key Qs:
  • Morning erections? (Loss is specific).
  • Shaving frequency? (Decreased).
  • Medications? (Opioids, Steroids).
  • Headaches/Vision? (Prolactinoma).
  • Children? (Fertility issues).

Station 2: Counselling (Starting TRT)

• Scenario: Discussing T-Gel.
• Key Points:
  • "Safety: Transfer risk to kids/wife (wash hands, cover up)."
  • "Complications: Thick blood (stroke risk), Prostate checks, Infertility."
  • "Expectations: Libido improves first (3-6 weeks); Erections/Depression take longer (3-6 months)."

Station 3: The "Bodybuilder" (Anabolic Steroids)

• Scenario: 25yo, huge muscles, disastrous libido, tiny testes.
• Diagnosis: Anabolic Steroid Induced Hypogonadism (ASIH).
• Management: STOP steroids. Do NOT give TRT (it perpetuates the suppression). Recover axis with hCG/Clomifene over months.

Viva Questions

Q: Why do we measure testosterone in the morning? A: Testosterone has a circadian rhythm, peaking at 08:00 and troughing at 20:00. Young men can have a 40% drop by afternoon, leading to false-positive diagnoses of hypogonadism.

Q: Interpret this: Low Testosterone, Low LH, High Prolactin. A: Secondary Hypogonadism caused by a Prolactinoma (suppressing GnRH). Needs MRI Pituitary and Dopamine Agonist (Cabergoline).

Q: Interpret this: Low Testosterone, High LH, High Ferritin. A: Primary Hypogonadism caused by Haemochromatosis (Iron deposition in testes). Note: Iron can also deposit in pituitary causing Secondary failure.

Q: How does obesity cause low testosterone? A: Adipose tissue has high aromatase activity, converting T to Oestradiol. Oestradiol exerts negative feedback on the pituitary, lowering LH and T. It also increases insulin resistance, lowering SHBG.

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16. References

Clinical Guidelines & Systematic Reviews

1. Bhasin S, Brito JP, Cunningham GR, Hayes FJ, Hodis HN, Matsumoto AM, Snyder PJ, Swerdloff RS, Wu FC, Yialamas MA. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. PMID: 29562364 DOI: 10.1210/jc.2018-00229

2. Salonia A, Bettocchi C, Carvalho J, Corona G, Jones TH, Kadioglu A, Martinez-Salamanca JI, Minhas S, Serefoglu EC, Verze P. EAU Guidelines on Sexual and Reproductive Health. European Association of Urology. 2023. ISBN: 978-94-92671-19-6

3. Lunenfeld B, Mskhalaya G, Zitzmann M, Corona G, Arver S, Kalinchenko S, Tishova Y, Morgentaler A. Recommendations on the diagnosis, treatment and monitoring of hypogonadism in men. Aging Male. 2015;18(1):5-15. PMID: 25657080 DOI: 10.3109/13685538.2015.1004049

Diagnostic & Laboratory Standards

4. Bhasin S, Cunningham GR, Hayes FJ, Matsumoto AM, Snyder PJ, Swerdloff RS, Montori VM; Task Force, Endocrine Society. Testosterone therapy in men with androgen deficiency syndromes: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2010;95(6):2536-2559. PMID: 20525905 DOI: 10.1210/jc.2009-2354

5. Wang C, Nieschlag E, Swerdloff R, Behre HM, Hellstrom WJ, Gooren LJ, Kaufman JM, Legros JJ, Lunenfeld B, Morales A, Morley JE, Schulman C, Thompson IM, Weidner W, Wu FC. Investigation, treatment, and monitoring of late-onset hypogonadism in males: ISA, ISSAM, EAU, EAA, and ASA recommendations. J Androl. 2009;30(1):1-9. PMID: 18772488 DOI: 10.2164/jandrol.108.006486

6. Boehm U, Bouloux PM, Dattani MT, de Roux N, Dodé C, Dunkel L, Dwyer AA, Giacobini P, Hardelin JP, Juul A, Maghnie M, Pitteloud N, Prevot V, Raivio T, Tena-Sempere M, Quinton R, Young J. Expert consensus document: European Consensus Statement on congenital hypogonadotropic hypogonadism--pathogenesis, diagnosis and treatment. Nat Rev Endocrinol. 2015;11(9):547-564. PMID: 26194704 DOI: 10.1038/nrendo.2015.112

7. Dwyer AA, Raivio T, Pitteloud N. Gonadotrophin replacement for induction of fertility in hypogonadal men. Best Pract Res Clin Endocrinol Metab. 2015;29(1):91-103. PMID: 25617175 DOI: 10.1016/j.beem.2014.10.005

8. Dandona P, Dhindsa S. Update: Hypogonadotropic hypogonadism in type 2 diabetes and obesity. J Clin Endocrinol Metab. 2011;96(9):2643-2651. PMID: 21896895 DOI: 10.1210/jc.2010-2724

Testosterone Formulations & Pharmacokinetics

9. Lincoff AM, Bhasin S, Flevaris P, Mitchell LM, Basaria S, Boden WE, Cunningham GR, Granger CB, Khera M, Thompson IM Jr, Wang Q, Wolski K, Davey D, Kalahasti V, Khan N, Miller MG, Snabes MC, Chan A, Dubcenco E, Houchard A, Nissen SE; TRAVERSE Study Investigators. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107-117. PMID: 37326322 DOI: 10.1056/NEJMoa2215025

10. Swerdloff RS, Wang C, Cunningham G, Dobs A, Iranmanesh A, Matsumoto AM, Snyder PJ, Weber T, Longstreth J, Berman N. Long-term pharmacokinetics of transdermal testosterone gel in hypogonadal men. J Clin Endocrinol Metab. 2000;85(12):4500-4510. PMID: 11134099 DOI: 10.1210/jcem.85.12.7045

11. Schubert M, Minnemann T, Hübler D, Rouskova D, Christoph A, Oettel M, Ernst M, Mellinger U, Krone W, Jockenhövel F. Intramuscular testosterone undecanoate: pharmacokinetic aspects of a novel testosterone formulation during long-term treatment of men with hypogonadism. J Clin Endocrinol Metab. 2004;89(11):5429-5434. PMID: 15531493 DOI: 10.1210/jc.2004-0897

12. Nieschlag E, Buchter D, Von Eckardstein S, Abshagen K, Simoni M, Behre HM. Repeated intramuscular injections of testosterone undecanoate for substitution therapy in hypogonadal men. Clin Endocrinol (Oxf). 1999;51(6):757-763. PMID: 10619981 DOI: 10.1046/j.1365-2265.1999.00881.x

13. Gooren LJ. A ten-year safety study of the oral androgen testosterone undecanoate. J Androl. 1994;15(3):212-215. PMID: 7928661

14. Handelsman DJ, Conway AJ, Boylan LM. Suppression of human spermatogenesis by testosterone implants. J Clin Endocrinol Metab. 1992;75(5):1326-1332. PMID: 1430094 DOI: 10.1210/jcem.75.5.1430094

15. Snyder PJ, Bhasin S, Cunningham GR, Matsumoto AM, Stephens-Shields AJ, Cauley JA, Gill TM, Barrett-Connor E, Swerdloff RS, Wang C, Ensrud KE, Lewis CE, Farrar JT, Cella D, Rosen RC, Pahor M, Crandall JP, Molitch ME, Cifelli D, Dougar D, Fluharty L, Resnick SM, Storer TW, Anton S, Basaria S, Diem SJ, Hou X, Mohler ER 3rd, Parsons JK, Wenger NK, Zeldow B, Landis JR, Ellenberg SS; Testosterone Trials Investigators. Effects of Testosterone Treatment in Older Men. N Engl J Med. 2016;374(7):611-624. PMID: 26886521 DOI: 10.1056/NEJMoa1506119

16. Ramasamy R, Armstrong JM, Lipshultz LI. Preserving fertility in the hypogonadal patient: an update. Asian J Androl. 2015;17(2):197-200. PMID: 25432497 DOI: 10.4103/1008-682X.145789

17. Nieschlag E, Behre HM, Bouchard P, Corrales JJ, Jones TH, Stalla GK, Webb SM, Wu FC. Testosterone replacement therapy: current trends and future directions. Hum Reprod Update. 2004;10(5):409-419. PMID: 15297434 DOI: 10.1093/humupd/dmh035

18. Drinka PJ, Jochen AL, Cuisinier M, Bloom R, Rudman I, Rudman D. Polycythemia as a complication of testosterone replacement therapy in nursing home men with low testosterone levels. J Am Geriatr Soc. 1995;43(8):899-901. PMID: 7636098 DOI: 10.1111/j.1532-5415.1995.tb05534.x

Fertility Preservation & Induction

19. Liu PY, Turner L, Rushford D, McDonald J, Baker HW, Conway AJ, Handelsman DJ. Efficacy and safety of recombinant human follicle stimulating hormone (Gonal-F) with urinary human chorionic gonadotrophin for induction of spermatogenesis and fertility in gonadotrophin-deficient men. Hum Reprod. 2002;17(2):404-408. PMID: 11821287 DOI: 10.1093/humrep/17.2.404

20. Shiraishi K, Oka S, Matsuyama H. Assessment of quality of life during gonadotropin treatment for male hypogonadotropic hypogonadism. Clin Endocrinol (Oxf). 2014;81(2):259-265. PMID: 24383912 DOI: 10.1111/cen.12413

21. Burris AS, Rodbard HW, Winters SJ, Sherins RJ. Gonadotropin therapy in men with isolated hypogonadotropic hypogonadism: the response to human chorionic gonadotropin is predicted by initial testicular size. J Clin Endocrinol Metab. 1988;66(6):1144-1151. PMID: 2897197 DOI: 10.1210/jcem-66-6-1144

22. Dwyer AA, Sykiotis GP, Hayes FJ, Boepple PA, Lee H, Loughlin KR, Dym M, Sluss PM, Crowley WF Jr, Pitteloud N. Trial of recombinant follicle-stimulating hormone pretreatment for GnRH-induced fertility in patients with congenital hypogonadotropic hypogonadism. J Clin Endocrinol Metab. 2013;98(11):E1790-1795. PMID: 24037884 DOI: 10.1210/jc.2013-2518

23. Guay AT, Jacobson J, Perez JB, Hodge MB, Velasquez E. Clomiphene increases free testosterone levels in men with both secondary hypogonadism and erectile dysfunction: who does and does not benefit? Int J Impot Res. 2003;15(3):156-165. PMID: 12904801 DOI: 10.1038/sj.ijir.3900981

24. Shabsigh A, Kang Y, Shabsign R, Gonzalez M, Liberson G, Fisch H, Goluboff E. Clomiphene citrate effects on testosterone/estrogen ratio in male hypogonadism. J Sex Med. 2005;2(5):716-721. PMID: 16422830 DOI: 10.1111/j.1743-6109.2005.00075.x

25. Taylor F, Levine L. Clomiphene citrate and testosterone gel replacement therapy for male hypogonadism: efficacy and treatment cost. J Sex Med. 2010;7(1 Pt 1):269-276. PMID: 19732304 DOI: 10.1111/j.1743-6109.2009.01454.x

26. Chua ME, Escusa KG, Luna S, Tapia LC, Dofitas B, Morales M. Revisiting oestrogen antagonists (clomiphene or tamoxifen) as medical empiric therapy for idiopathic male infertility: a meta-analysis. Andrology. 2013;1(5):749-757. PMID: 23970453 DOI: 10.1111/j.2047-2927.2013.00107.x

27. Wiehle R, Cunningham GR, Pitteloud N, Wike J, Hsu K, Podolski JS, Sitruk-Ware R, Kumar N, Steiner M, Blithe D, Olson R. Testosterone restoration using enclomiphene citrate in men with secondary hypogonadism: pharmacokinetics and area under the curve linearity. BJU Int. 2013;112(8):1188-1200. PMID: 23937331 DOI: 10.1111/bju.12363

28. Saal W, Glowania HJ, Hengst W, Happ J. Pharmacodynamics and pharmacokinetics after subcutaneous and intramuscular injection of human chorionic gonadotropin. Fertil Steril. 1991;56(2):225-229. PMID: 2070850 DOI: 10.1016/s0015-0282(16)54476-8

29. Rohayem J, Sinthofen N, Nieschlag E, Kliesch S, Zitzmann M. Causes of hypogonadotropic hypogonadism predict response to gonadotropin substitution in adults. Andrology. 2016;4(1):87-94. PMID: 26663756 DOI: 10.1111/andr.12128

30. Samplaski MK, Lo KC, Grober ED, Zini A, Jarvi KA. Testosterone use in the male infertility population: prescribing patterns and effects on semen and hormonal parameters. Fertil Steril. 2014;101(1):64-69. PMID: 24140033 DOI: 10.1016/j.fertnstert.2013.09.003

31. Patel AS, Leong JY, Ramasamy R, Blaschko SD. Testosterone is a contraceptive and should not be used in men who desire fertility. World J Mens Health. 2019;37(1):45-54. PMID: 29756416 DOI: 10.5534/wjmh.180036

32. Coward RM, Rajanahally S, Kovac JR, Smith RP, Pastuszak AW, Lipshultz LI. Anabolic steroid induced hypogonadism in young men. J Urol. 2013;190(6):2200-2205. PMID: 23764075 DOI: 10.1016/j.juro.2013.06.010

33. Wenker EP, Dupree JM, Langille GM, Kovac JR, Ramasamy R, Lamb DJ, Lipshultz LI. The use of HCG-based combination therapy for recovery of spermatogenesis after testosterone use. J Sex Med. 2015;12(6):1334-1337. PMID: 25914386 DOI: 10.1111/jsm.12905

Cardiovascular Safety & Mortality

34. Khaw KT, Dowsett M, Folkerd E, Bingham S, Wareham N, Luben R, Welch A, Day N. Endogenous testosterone and mortality due to all causes, cardiovascular disease, and cancer in men: European prospective investigation into cancer in Norfolk (EPIC-Norfolk) Prospective Population Study. Circulation. 2007;116(23):2694-2701. PMID: 18040028 DOI: 10.1161/CIRCULATIONAHA.107.719005

35. Shores MM, Matsumoto AM, Sloan KL, Kivlahan DR. Low serum testosterone and mortality in male veterans. Arch Intern Med. 2006;166(15):1660-1665. PMID: 16908801 DOI: 10.1001/archinte.166.15.1660

36. Araujo AB, Dixon JM, Suarez EA, Murad MH, Guey LT, Wittert GA. Clinical review: Endogenous testosterone and mortality in men: a systematic review and meta-analysis. J Clin Endocrinol Metab. 2011;96(10):3007-3019. PMID: 21816776 DOI: 10.1210/jc.2011-1137

37. Muraleedharan V, Marsh H, Kapoor D, Channer KS, Jones TH. Testosterone deficiency is associated with increased risk of mortality and testosterone replacement improves survival in men with type 2 diabetes. Eur J Endocrinol. 2013;169(6):725-733. PMID: 24008902 DOI: 10.1530/EJE-13-0321

38. Corona G, Rastrelli G, Monami M, Guay A, Buvat J, Sforza A, Forti G, Mannucci E, Maggi M. Hypogonadism as a risk factor for cardiovascular mortality in men: a meta-analytic study. Eur J Endocrinol. 2011;165(5):687-701. PMID: 21852391 DOI: 10.1530/EJE-11-0447

39. Malkin CJ, Pugh PJ, West JN, van Beek EJ, Jones TH, Channer KS. Testosterone therapy in men with moderate severity heart failure: a double-blind randomized placebo controlled trial. Eur Heart J. 2006;27(1):57-64. PMID: 16093267 DOI: 10.1093/eurheartj/ehi443

40. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107-117. PMID: 37326322 DOI: 10.1056/NEJMoa2215025

41. Budoff MJ, Ellenberg SS, Lewis CE, Mohler ER 3rd, Wenger NK, Bhasin S, Barrett-Connor E, Swerdloff RS, Stephens-Shields A, Cauley JA, Crandall JP, Cunningham GR, Ensrud KE, Gill TM, Matsumoto AM, Molitch ME, Nakanishi R, Nezarat N, Matsumoto S, Hou X, Basaria S, Diem SJ, Wang C, Cifelli D, Snyder PJ. Testosterone Treatment and Coronary Artery Plaque Volume in Older Men With Low Testosterone. JAMA. 2017;317(7):708-716. PMID: 28241356 DOI: 10.1001/jama.2016.21043

42. Basaria S, Coviello AD, Travison TG, Storer TW, Farwell WR, Jette AM, Eder R, Tennstedt S, Ulloor J, Zhang A, Choong K, Lakshman KM, Mazer NA, Miciek R, Krasnoff J, Elmi A, Knapp PE, Brooks B, Appleman E, Aggarwal S, Bhasin G, Hede-Brierley L, Bhatia A, Collins L, LeBrasseur N, Fiore LD, Bhasin S. Adverse events associated with testosterone administration. N Engl J Med. 2010;363(2):109-122. PMID: 20592293 DOI: 10.1056/NEJMoa1000485

43. Corona G, Giagulli VA, Maseroli E, Vignozzi L, Aversa A, Zitzmann M, Saad F, Mannucci E, Maggi M. Therapy of endocrine disease: Testosterone supplementation and body composition: results from a meta-analysis study. Eur J Endocrinol. 2016;174(3):R99-116. PMID: 26537862 DOI: 10.1530/EJE-15-0262

44. Hudson J, Cruickshank M, Quinton R, Aucott L, Aceves-Martins M, Banner NR, Gale CP, Giebe S, Gomez D, Herd C, Newby DE, Ross H, van Veldhuisen DJ, Witte KK, Wu FC, Sharma R. Adverse cardiovascular events and mortality in men during testosterone treatment: an individual patient and aggregate data meta-analysis. Lancet Healthy Longev. 2022;3(6):e381-e393. PMID: 35711612 DOI: 10.1016/S2666-7568(22)00096-4

Emerging Therapies

45. Swerdloff RS, Wang C, White WB, Kaminetsky J, Gittelman MC, Longstreth JA, Dudley RE, Danoff TM. A new oral testosterone undecanoate formulation restores testosterone to normal concentrations in hypogonadal men. J Clin Endocrinol Metab. 2020;105(8):2515-2531. PMID: 32232429 DOI: 10.1210/clinem/dgaa238

46. Wittert G, Bracken K, Robledo KP, Grossmann M, Yeap BB, Handelsman DJ, Stuckey B, Conway A, Inder W, McLachlan R, Allan C, Jesudason D, Fui MN, Hoermann R, Ng Tang Fui M, Jenkins A, Keech A, Huisman M, Clifton P, Hague W. Testosterone treatment to prevent or revert type 2 diabetes in men enrolled in a lifestyle programme (T4DM): a randomised, double-blind, placebo-controlled, 2-year, phase 3b trial. Lancet Diabetes Endocrinol. 2021;9(1):32-45. PMID: 33271079 DOI: 10.1016/S2213-8587(20)30367-3

47. Sharma A, Jayasena CN, Dhillo WS. Regulation of the hypothalamic-pituitary-testicular axis: Pathophysiology of hypogonadism. Endocrinol Metab Clin North Am. 2022;51(1):29-45. PMID: 35216719 DOI: 10.1016/j.ecl.2021.11.010

48. Solomon ZJ, Mirabal JR, Mazur DJ, Kohn TP, Lipshultz LI, Pastuszak AW. Selective androgen receptor modulators (SARMs)-current knowledge and clinical applications. Sex Med Rev. 2019;7(1):84-94. PMID: 30253091 DOI: 10.1016/j.sxmr.2018.09.006

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Glossary of Terms