Primary Hyperparathyroidism

1. Clinical Overview

Summary

Primary Hyperparathyroidism (PHPT) is a disorder of inappropriate parathyroid hormone (PTH) hypersecretion, resulting in hypercalcaemia and disturbances in calcium-phosphate homeostasis. It is the most common cause of hypercalcaemia in the outpatient setting and the third most common endocrine disorder after diabetes mellitus and thyroid disease. [1,2]

The condition is usually caused by a solitary parathyroid adenoma (80-85% of cases), though multigland hyperplasia (10-15%) and double adenomas (2-5%) also occur. Parathyroid carcinoma is rare, accounting for less than 1% of cases. [3]

While the classic presentation involves "bones, stones, abdominal groans, and psychic moans," the contemporary phenotype has dramatically shifted. Modern biochemical screening has resulted in most patients (approximately 80%) being asymptomatic at diagnosis ("biochemical PHPT"), with mild hypercalcaemia detected incidentally on routine blood panels. This asymptomatic presentation raises important questions about optimal management strategies, balancing the high cure rate of surgery against the risks of intervention in minimally symptomatic patients. [4,5]

Definitive management is surgical parathyroidectomy, which achieves cure rates exceeding 95% in experienced centres. Surgery is clearly indicated for all symptomatic patients and asymptomatic patients meeting specific criteria defined by international consensus guidelines (age less than 50 years, serum calcium more than 0.25 mmol/L above upper limit, renal or bone involvement). For patients not meeting surgical criteria or those unfit for surgery, conservative monitoring with or without pharmacological therapy represents an acceptable alternative. [6,7]

Key Facts

• Incidence: 1-7 per 1,000 adults in Western populations; peak incidence in post-menopausal women aged 50-60 years.
• Gender Ratio: Female to male ratio approximately 3-4:1 overall, increasing to 8:1 in post-menopausal women. [1]
• Aetiology: Solitary adenoma (80-85%), Multi-gland hyperplasia (10-15%), Double adenoma (2-5%), Carcinoma (less than 1%). [3]
• Biochemical Profile: Hypercalcaemia + Elevated (or inappropriately normal) PTH + Low or low-normal phosphate.
• Diagnostic Exclusion: Familial Hypocalciuric Hypercalcaemia (FHH) must be excluded before proceeding to surgery.
• Treatment: Surgical parathyroidectomy is the only curative therapy (cure rate greater than 95%). [8]
• Localisation: Technetium-99m sestamibi scan and neck ultrasound are standard pre-operative localisation modalities.

Clinical Pearls

Inappropriately Normal PTH is Diagnostic: A patient with hypercalcaemia should have a SUPPRESSED PTH (e.g., less than 1.0 pmol/L). If serum calcium is elevated at 2.8 mmol/L and PTH is "normal" (e.g., 4.5 pmol/L, within laboratory reference range 1.6-6.9 pmol/L), this represents Primary Hyperparathyroidism. The PTH is inappropriate for the calcium level. This is a fundamental concept frequently tested in examinations.

Exclude FHH Before Surgery: Before referring for parathyroidectomy, check the 24-hour urinary calcium and calculate the calcium-to-creatinine clearance ratio (CCCR). Familial Hypocalciuric Hypercalcaemia (FHH) is a benign autosomal dominant condition that mimics PHPT biochemically but does not benefit from surgery. Low urine calcium (CCCR less than 0.01) suggests FHH, which should prompt genetic testing for calcium-sensing receptor (CaSR) mutations. [9]

Hungry Bone Syndrome: After removing a parathyroid adenoma in a patient with severe bone disease (elevated alkaline phosphatase, advanced osteoporosis), the "starved" bones rapidly uptake calcium, phosphate, and magnesium, causing severe and prolonged post-operative hypocalcaemia. Patients require careful monitoring and aggressive calcium and vitamin D supplementation. Watch for perioral tingling, paraesthesias, and Chvostek's or Trousseau's signs.

Normocalcaemic PHPT: A recognized variant where serum calcium is persistently normal but PTH is consistently elevated. This diagnosis requires exclusion of secondary causes of PTH elevation (vitamin D deficiency, chronic kidney disease, malabsorption, medications such as lithium). Approximately 0.4% of the general population and up to 30% of patients with osteoporosis or nephrolithiasis may have normocalcaemic PHPT. These patients may progress to classic hypercalcaemic PHPT and can develop skeletal and renal complications. [10]

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2. Epidemiology

Incidence and Demographics

Primary hyperparathyroidism is one of the most common endocrine disorders encountered in clinical practice. Its prevalence has increased substantially since the 1970s following the widespread introduction of automated biochemistry screening panels that include serum calcium measurement. [1]

Prevalence and Incidence:

• General Population: Prevalence ranges from 0.3% to 0.86% in community-based studies.
• Post-menopausal Women: Prevalence increases to 2-3% in post-menopausal women, the highest-risk demographic group.
• Annual Incidence: Approximately 66 per 100,000 person-years in women and 25 per 100,000 person-years in men. [1,2]
• Age-Related Increase: Incidence rises progressively with age, peaking in the sixth and seventh decades of life.

Demographic Risk Factors:

Geographical and Ethnic Variations:

• Higher rates reported in Scandinavia and North America compared to Asia and Africa.
• Some variation may reflect differences in biochemical screening practices rather than true incidence differences.
• African Americans may present with more advanced disease compared to Caucasians. [11]

Aetiology and Genetics

Sporadic PHPT (90-95% of cases):

The majority of primary hyperparathyroidism is sporadic, with no identifiable familial or genetic cause. The pathological subtypes include:

1. Solitary Adenoma (80-85%):

   • Single gland involvement with remaining glands suppressed and atrophic.
   • Adenomas are benign monoclonal proliferations of chief cells.
   • Average weight 0.5-1 gram; normal parathyroid glands weigh 30-40 mg each.
   • Most commonly arise from inferior parathyroid glands.

2. Double Adenoma (2-5%):

   • Two glands enlarged, remaining two normal or suppressed.
   • Diagnostic challenge at surgery; intraoperative PTH monitoring helpful.

3. Multigland Hyperplasia (10-15%):

   • All four glands enlarged (asymmetrically).
   • More common in familial syndromes but can be sporadic.
   • Higher risk of persistent or recurrent disease after surgery.

4. Parathyroid Carcinoma (less than 1%):

   • Rare malignancy with distinct clinical features.
   • Consider with very high calcium (greater than 3.5 mmol/L), very high PTH (greater than 5-10x upper limit).
   • Palpable neck mass, local invasion, and distant metastases possible.
   • Associated with CDC73 (HRPT2) germline mutations in hereditary forms. [3]

Familial/Syndromic PHPT (5-10% of cases):

Genetic Testing Indications:

• PHPT diagnosed before age 40
• Multigland disease
• Family history of endocrine tumours
• Parathyroid carcinoma
• Recurrent PHPT after surgery [12]

Pathophysiology at the Molecular Level

Normal Calcium Homeostasis

Calcium homeostasis is tightly regulated through a sophisticated endocrine axis involving parathyroid hormone (PTH), vitamin D, and calcitonin, with actions at three key sites: bone, kidney, and intestine.

Parathyroid Calcium Sensing:

• Parathyroid chief cells express the Calcium-Sensing Receptor (CaSR), a G-protein coupled receptor on their cell surface.
• High Serum Calcium → Activates CaSR → Inhibits PTH secretion.
• Low Serum Calcium → Reduces CaSR activation → Stimulates PTH secretion.
• This negative feedback loop maintains serum calcium within a narrow physiological range (2.2-2.6 mmol/L). [13]

Normal PTH Actions:

Vitamin D Metabolism:

• PTH activates renal 1-alpha-hydroxylase, converting 25-hydroxyvitamin D to the active 1,25-dihydroxyvitamin D (calcitriol).
• Calcitriol enhances intestinal calcium and phosphate absorption.

Pathophysiology of PHPT

In primary hyperparathyroidism, autonomous or semi-autonomous secretion of PTH occurs despite elevated serum calcium, due to:

1. Set-Point Error:

   • The neoplastic parathyroid tissue has a higher set-point for calcium suppression.
   • Higher calcium levels are required to suppress PTH secretion.
   • This can result from reduced CaSR expression or mutations in CaSR signaling pathways. [13]

2. Autonomous Secretion:

   • In severe cases, PTH secretion becomes completely autonomous, unresponsive to calcium levels.
   • Loss of normal negative feedback regulation.

3. Cellular Proliferation:

   • Monoclonal expansion of parathyroid cells (in adenomas).
   • Mutations in cell cycle regulators (e.g., MEN1, CCND1 cyclin D1 overexpression).
   • Increased parathyroid cell mass amplifies PTH secretion even if per-cell secretion is normal.

Consequences of Chronic PTH Excess:

1. Kidney Effects:

• Hypercalciuria: Despite PTH-mediated tubular calcium reabsorption, the filtered calcium load overwhelms reabsorption capacity.
• Nephrolithiasis: Calcium oxalate or calcium phosphate stones form in 15-20% of patients. [14]
• Nephrocalcinosis: Calcium deposition in renal parenchyma, potentially leading to chronic kidney disease.
• Polyuria and Polydipsia: Hypercalcaemia impairs urinary concentrating ability (nephrogenic diabetes insipidus).
• Renal Impairment: eGFR declines in approximately 10-15% of patients with PHPT.

2. Skeletal Effects:

• Cortical Bone Loss: PTH preferentially affects cortical bone (distal radius, hip) more than trabecular bone (spine).
• Osteitis Fibrosa Cystica: Classic severe manifestation, now rare in developed countries:
  • Subperiosteal bone resorption (radial aspect of middle phalanges, distal clavicle).
  • Brown tumours (osteoclast-rich lytic lesions).
  • "Pepper-pot skull" appearance.
  • "Rugger jersey spine" from sclerotic bands at vertebral endplates.
• Osteoporosis: 30-50% of patients meet DEXA criteria for osteoporosis (T-score less than -2.5).
• Fracture Risk: Increased risk of vertebral and non-vertebral fractures. [15]

3. Gastrointestinal Effects:

• Peptic Ulcer Disease: Calcium stimulates gastrin secretion (Zollinger-Ellison-like effect).
• Pancreatitis: Hypercalcaemia activates pancreatic enzymes prematurely (2-7% of PHPT patients).
• Constipation: Hypercalcaemia reduces intestinal motility.
• Nausea and Anorexia: Direct effects of hypercalcaemia on the gastrointestinal tract.

4. Neuromuscular and Neuropsychiatric Effects:

• Proximal Myopathy: Difficulty rising from a chair or climbing stairs.
• Depression and Anxiety: Reported in 30-50% of patients; mechanism unclear.
• Cognitive Impairment: "Brain fog," memory problems, reduced concentration.
• Fatigue: One of the most common symptoms, often unrecognized until post-operative resolution. [16]

5. Cardiovascular Effects:

• Hypertension: Present in 40-75% of patients; may improve after parathyroidectomy.
• Left Ventricular Hypertrophy: PTH has direct effects on cardiac myocytes.
• Vascular Calcification: Increased cardiovascular mortality in severe PHPT.
• Arrhythmias: Short QT interval on ECG; theoretical risk of arrhythmias, though clinical significance uncertain.

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3. Clinical Presentation

Historical Context

The clinical presentation of PHPT has evolved dramatically over the past 50 years. Prior to the 1970s, patients presented with advanced symptomatic disease: nephrolithiasis, severe bone disease (osteitis fibrosa cystica), and overt hypercalcaemic symptoms. The introduction of automated biochemistry panels including serum calcium measurement transformed PHPT into predominantly an asymptomatic biochemical diagnosis. [4]

Asymptomatic ("Biochemical") PHPT (Approximately 80%)

The majority of contemporary patients are asymptomatic or minimally symptomatic at diagnosis.

Typical Presentation:

• Incidental hypercalcaemia detected on routine blood work (health screening, pre-operative assessment, evaluation for other conditions).
• Mild hypercalcaemia (2.6-2.85 mmol/L).
• Patient feels "well" or attributes vague symptoms to aging or stress.
• Retrospective symptom recognition after surgical cure is common (fatigue, mood changes, cognitive symptoms). [5]

Challenging Diagnostic Questions:

• Are these patients truly asymptomatic, or do they have subtle symptoms not recognized?
• Does early intervention prevent progression to symptomatic disease?
• What is the natural history of untreated asymptomatic PHPT?

Symptomatic PHPT (Approximately 20%)

Classic mnemonic: "Bones, Stones, Abdominal Groans, and Psychic Moans"

Renal Manifestations ("Stones")

Note: Approximately 3-5% of patients with recurrent calcium nephrolithiasis have underlying PHPT. All patients with recurrent calcium stones should have serum calcium and PTH checked. [14]

Skeletal Manifestations ("Bones")

DEXA Findings in PHPT:

• Distal 1/3 radius (cortical site): Most sensitive; shows greatest bone loss.
• Femoral neck (mixed cortical/trabecular): Intermediate bone loss.
• Lumbar spine (trabecular): Relatively preserved or even increased density (effect of high PTH on trabecular bone remodelling). [15]

Gastrointestinal Manifestations ("Abdominal Groans")

Neuropsychiatric Manifestations ("Psychic Moans")

Neuropsychiatric Controversy: The relationship between PHPT and neuropsychiatric symptoms is debated. Some studies show improvement after parathyroidectomy; others show no difference compared to observation. Patient selection and subjective outcome measures complicate interpretation. [16]

Neuromuscular Manifestations

Cardiovascular Manifestations

Hypercalcaemic Crisis (Parathyroid Storm)

A rare but life-threatening complication:

• Serum Calcium: Typically greater than 3.5-4.0 mmol/L (14-16 mg/dL).
• Clinical Features: Severe dehydration, altered mental status, nausea/vomiting, acute kidney injury, arrhythmias, coma.
• Triggers: Dehydration, immobilization, acute illness, thiazide diuretics.
• Management: Medical emergency requiring aggressive IV hydration, calcitonin, bisphosphonates, and urgent parathyroidectomy. [17]

Red Flags for Parathyroid Carcinoma

Histological Features: Capsular invasion, vascular invasion, mitotic activity (though histology alone can be challenging; clinical and intraoperative findings critical). [3]

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4. Clinical Examination

General Inspection

Overall Appearance:

• Most patients with mild PHPT appear well.
• Severe chronic PHPT: Cachexia, bone deformities, signs of chronic illness.

Signs of Hypercalcaemia:

• Dehydration: Dry mucous membranes, reduced skin turgor (hypercalcaemia causes polyuria).
• Confusion: Altered mental status in severe hypercalcaemia.
• Band Keratopathy: Calcium deposition in cornea (medial and lateral limbus); visible as white horizontal bands; rare.

Neck Examination

Key Point: A normal neck examination is expected in PHPT due to solitary adenoma.

Inspection:

• Look for previous thyroid surgery scars (bilateral neck exploration scar).
• Assess for visible neck masses (should be absent in adenoma).

Palpation:

• Normal Finding: No palpable mass. A typical parathyroid adenoma weighs 0.5-1 gram and is located deep to the thyroid, making it non-palpable.
• Abnormal Finding: Palpable neck mass raises concern for:
  • "Parathyroid Carcinoma: Hard, fixed, irregular mass."
  • "Thyroid Nodule: Moves with swallowing; may co-exist with PHPT."
  • "Large Adenoma: Rarely, very large adenomas (greater than 3-4 cm) may be palpable."

Vocal Cord Assessment:

• Assess voice quality (hoarseness may indicate recurrent laryngeal nerve involvement in carcinoma).
• Formal laryngoscopy should be considered if voice changes present.

Skeletal Examination

Vertebral Tenderness:

• Palpate spine for focal tenderness (vertebral compression fractures).
• Assess kyphosis or loss of height.

Proximal Myopathy Testing:

• Chair Rise Test: Ask patient to stand from seated position without using arms.
• Squat Test: Ask patient to squat and rise (tests quadriceps strength).
• Shoulder Abduction: Assess deltoid strength (ask patient to hold arms extended; apply downward pressure).

Bone Deformities:

• Limb deformities (rare; severe osteitis fibrosa cystica).
• Mandibular or maxillary masses (hyperparathyroidism-jaw tumour syndrome).

Neuromuscular Examination

Tone and Power:

• Proximal muscle weakness (hip flexors, shoulder abductors).
• Normal or slightly reduced tone.

Reflexes:

• Typically normal or brisk.

Gait:

• Waddling gait if proximal muscle weakness present.
• Assess for ataxia or gait instability (risk of falls).

Associated Endocrinopathy Assessment (If Familial Syndrome Suspected)

MEN1:

• Pituitary tumours: Visual field defects (bitemporal hemianopia from pituitary macroadenoma).
• Pancreatic tumours: Epigastric masses (rare); symptoms of gastrinoma (peptic ulcer disease), insulinoma (hypoglycaemia).

MEN2A:

• Thyroid nodule (medullary thyroid cancer): Palpable thyroid nodule, cervical lymphadenopathy.
• Phaeochromocytoma: Hypertension, tachycardia, sweating (paroxysmal symptoms).

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5. Investigations

Biochemical Diagnosis

The diagnosis of PHPT is biochemical, based on the combination of hypercalcaemia and elevated (or inappropriately normal) PTH.

Initial Biochemistry Panel

Critical Point: Vitamin D Repletion Before Diagnosis:

• Vitamin D deficiency stimulates secondary hyperparathyroidism (compensatory PTH elevation).
• Patients with mild hypercalcaemia and elevated PTH should have vitamin D levels checked.
• If 25(OH)D is less than 50 nmol/L (less than 20 ng/mL), replete with vitamin D supplementation.
• Re-check calcium and PTH after 3 months of repletion.
• If PTH normalizes, the diagnosis was secondary hyperparathyroidism, not PHPT.
• If PTH remains elevated despite vitamin D repletion, PHPT is confirmed. [2]

Exclusion of Familial Hypocalciuric Hypercalcaemia (FHH)

FHH is a benign autosomal dominant condition caused by inactivating mutations in the calcium-sensing receptor (CaSR) gene. It mimics PHPT biochemically but does not benefit from surgery.

Diagnostic Differentiation:

Calculation of CCCR:

CCCR = \frac{\text{Urine Calcium (mmol/L)} \times \text{Serum Creatinine (mmol/L)}}{\text{Serum Calcium (mmol/L)} \times \text{Urine Creatinine (mmol/L)}}

Action: If CCCR is less than 0.01 or clinical suspicion is high, consider genetic testing for CASR mutations before proceeding to surgery. [9]

Biochemical Markers of Bone Turnover

These markers are not routinely required for diagnosis but may be useful in research settings or monitoring response to therapy.

Imaging for Pre-Operative Localisation

Important Principle: Imaging is for localisation, not diagnosis. Biochemistry establishes the diagnosis; imaging guides surgical approach.

Localisation imaging is only performed if:

1. Surgery is planned.
2. The surgeon intends to perform a focused (minimally invasive) approach.

If bilateral neck exploration is planned, pre-operative localisation is optional.

First-Line Localisation Modalities

1. Technetium-99m Sestamibi Scan (MIBI Scan)

Principle:

• Sestamibi is a lipophilic cation taken up by mitochondria-rich tissue (parathyroid adenomas, thyroid, myocardium).
• Parathyroid adenomas retain tracer longer than thyroid tissue (delayed washout).
• Dual-phase imaging: Early phase (thyroid and parathyroid visible), Delayed phase (parathyroid adenoma remains visible, thyroid washed out).

Sensitivity:

• Solitary Adenoma: 80-90% sensitivity.
• Multigland Disease: 45-65% sensitivity (lower because hyperplastic glands are smaller and less avid).
• Smaller Adenomas: Sensitivity decreases for glands less than 500 mg.

Interpretation:

• Focal uptake persisting on delayed images indicates likely adenoma location.
• SPECT/CT fusion improves anatomical localization (distinguishes ectopic from orthotopic locations).

2. Neck Ultrasound

Principle:

• High-frequency ultrasound (7-15 MHz) identifies enlarged parathyroid glands.
• Parathyroid adenomas appear as hypoechoic, ovoid, homogeneous masses posterior or inferior to the thyroid.

Sensitivity:

• Experienced Operator: 70-80% sensitivity for identifying adenomas.
• Operator-Dependent: Sensitivity varies significantly with sonographer expertise.

Advantages:

• No radiation exposure.
• Identifies concurrent thyroid pathology (nodules, goitre).
• Can guide ultrasound-guided FNA if thyroid nodule co-exists.

Limitations:

• Cannot identify mediastinal or retrotracheal ectopic glands.
• Difficult in obese patients or patients with short necks.

Concordance Strategy:

• If MIBI and ultrasound are concordant (both identify the same location), proceed to focused parathyroidectomy.
• If discordant or negative, consider additional imaging or bilateral neck exploration. [18]

Second-Line Localisation Modalities

3. Four-Dimensional Computed Tomography (4D-CT)

Principle:

• Multi-phase contrast-enhanced CT (non-contrast, arterial, venous, delayed phases).
• Parathyroid adenomas enhance rapidly in arterial phase (high vascularity) and wash out in delayed phase.
• "Fourth dimension" refers to temporal changes in enhancement pattern.

Indications:

• Negative or discordant MIBI and ultrasound.
• Reoperative parathyroid surgery (identifying ectopic or recurrent adenomas).
• Suspected ectopic locations (mediastinum, retro-oesophageal, intrathyroidal).

Sensitivity:

• 70-85% overall.
• Superior to MIBI for ectopic glands.

Limitations:

• Radiation exposure (approximately 5-10 mSv).
• Contrast load (caution in renal impairment).

4. Magnetic Resonance Imaging (MRI)

Principle:

• T2-weighted images: Parathyroid adenomas appear hyperintense.
• Dynamic contrast-enhanced MRI: Similar to 4D-CT, assesses perfusion.

Indications:

• Failed first-line imaging.
• Reoperative surgery.
• Pregnancy (avoids radiation).
• Contrast allergy or renal impairment (non-contrast MRI).

Sensitivity:

• 70-80%; comparable to 4D-CT.

Limitations:

• Time-consuming.
• Expensive.
• Not widely available for routine parathyroid localization.

5. Selective Venous Sampling for PTH

Principle:

• Interventional radiology procedure.
• Catheterize neck and mediastinal veins; sample blood for PTH at multiple sites.
• Higher PTH concentration indicates proximity to hyperfunctioning gland.

Indications:

• Reoperative parathyroid surgery with negative non-invasive imaging.
• High-volume centres with experienced interventional radiologists.

Sensitivity:

• 70-90% in experienced hands.

Limitations:

• Invasive.
• Technically challenging.
• Not widely available.

Assessment of End-Organ Complications

Bone Assessment

Dual-Energy X-ray Absorptiometry (DEXA) Scan:

All patients with PHPT should undergo DEXA scanning to assess bone mineral density and fracture risk.

Sites to Measure:

1. Lumbar Spine (L1-L4): Trabecular bone; often relatively preserved in PHPT.
2. Femoral Neck and Total Hip: Mixed cortical and trabecular bone; moderate bone loss.
3. Distal 1/3 Radius (One-Third Radius Site): Cortical bone; most sensitive site for PTH-mediated bone loss; should always be included in PHPT assessment. [15]

Interpretation:

• T-score: Number of standard deviations from young adult mean.
  • "Normal: Greater than -1.0"
  • "Osteopenia: -1.0 to -2.5"
  • "Osteoporosis: Less than -2.5"
• Z-score: Comparison to age-matched controls; useful in younger patients.

Surgical Indication: T-score less than -2.5 at any site, or prior fragility fracture, is an indication for parathyroidectomy. [6]

Radiographs:

Not routinely required unless symptoms suggest specific findings.

Classic Findings in Severe Osteitis Fibrosa Cystica (Rare Today):

• Subperiosteal Resorption: Radial aspect of middle phalanges; distal clavicle; skull (salt-and-pepper or pepper-pot appearance).
• Brown Tumours: Lytic lesions (osteoclast-rich granulomas); can be mistaken for metastases.
• Rugger Jersey Spine: Sclerotic bands at vertebral endplates.
• Loss of Lamina Dura: Around teeth.

Renal Assessment

Renal Function:

• Serum creatinine and estimated glomerular filtration rate (eGFR).
• eGFR less than 60 mL/min/1.73m² is a surgical indication. [6]

Renal Imaging for Nephrolithiasis/Nephrocalcinosis:

Recommendation: Non-contrast CT is the preferred modality for comprehensive renal assessment in PHPT patients.

24-Hour Urinary Biochemistry:

Surgical Indication: Presence of nephrolithiasis or nephrocalcinosis on imaging is an indication for parathyroidectomy. [6]

Cardiovascular Assessment

Electrocardiogram (ECG):

• Short QT interval (QTc less than 360 ms) due to hypercalcaemia.
• Assess for arrhythmias (though uncommon).

Echocardiography:

• Not routinely required.
• Consider if symptoms of heart failure or if assessing left ventricular hypertrophy.

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6. Management

Management Overview: The Bilezikian Guidelines

Management of PHPT is guided by international consensus statements, most notably the Fourth International Workshop on Asymptomatic Primary Hyperparathyroidism (Bilezikian et al., 2014). These guidelines define surgical indications for asymptomatic patients. [6]

Surgical Management: Parathyroidectomy

Surgery is the only curative treatment for PHPT. It achieves cure rates exceeding 95% in experienced hands and provides long-term benefits for bone density, kidney function, and quality of life. [8]

Indications for Surgery

1. Symptomatic PHPT (Absolute Indications):

• Nephrolithiasis or nephrocalcinosis
• Osteoporosis (T-score less than -2.5 at any site) or fragility fracture
• Renal impairment (eGFR less than 60 mL/min/1.73m²)
• Hypercalcaemic crisis or severe hypercalcaemia (greater than 3.0 mmol/L)
• Pancreatitis attributable to hypercalcaemia
• Neuromuscular symptoms significantly affecting quality of life

2. Asymptomatic PHPT Meeting Fourth International Workshop Criteria [6]:

Surgery recommended if ANY of the following are met:

3. Patient Preference:

• Even if formal criteria not met, surgery is appropriate if the patient prefers definitive treatment after informed discussion of risks and benefits.

Surgical Approaches

1. Focused (Minimally Invasive) Parathyroidectomy (FP or MIP)

Principle:

• Based on concordant pre-operative localisation (MIBI + ultrasound identifying same gland).
• Small incision (2-3 cm) directly over identified gland.
• Remove single adenoma; other glands not routinely explored.

Advantages:

• Shorter operative time (30-45 minutes).
• Smaller scar; better cosmetic outcome.
• Reduced post-operative pain and hospital stay (often day-case or overnight).
• Faster recovery.

Requirements:

• Concordant imaging (both MIBI and ultrasound positive for same location).
• Intraoperative PTH monitoring to confirm cure (see below).
• Experienced surgeon.

Success Rate: Greater than 95% cure in appropriately selected patients. [8]

2. Bilateral Neck Exploration (BNE)

Principle:

• Identify and inspect all four parathyroid glands.
• Remove all abnormal glands; leave at least one normal or partial normal gland to prevent permanent hypoparathyroidism.

Indications:

• Negative or discordant pre-operative localisation.
• Multigland disease suspected (familial syndromes, secondary/tertiary hyperparathyroidism).
• Reoperative surgery (previous failed parathyroidectomy).
• Surgeon preference or limited access to intraoperative PTH.

Advantages:

• Allows comprehensive assessment of all glands.
• Higher success rate in multigland disease.

Disadvantages:

• Longer operative time (90-120 minutes).
• Larger incision.
• Higher risk of recurrent laryngeal nerve injury and hypoparathyroidism (if inadvertent removal of multiple glands).

Success Rate: 95-98% cure in experienced hands. [8]

3. Intraoperative Parathyroid Hormone (IOPTH) Monitoring

Principle:

• PTH has a short half-life (3-5 minutes).
• Measure baseline PTH before incision.
• Measure PTH at 5 and 10 minutes after adenoma excision.
• A drop of greater than 50% from baseline (Miami criteria) confirms removal of all hyperfunctioning tissue and predicts cure.

Miami Criteria:

\text{PTH Drop} \geq 50\% \text{ from baseline or pre-excision level at 10 minutes post-excision}

Advantages:

• Real-time confirmation of biochemical cure.
• Reduces need for bilateral exploration in single adenoma cases.
• Identifies missed second adenomas or multigland disease (persistent PTH elevation despite removal of one gland).

Sensitivity and Specificity: Greater than 95% for predicting cure. [19]

Limitations:

• Requires specialized laboratory support (rapid PTH assay).
• False positives/negatives rare (e.g., coexisting vitamin D deficiency may blunt PTH drop).

Surgical Complications

Hungry Bone Syndrome Risk Factors [20]:

• High pre-operative alkaline phosphatase (greater than 2-3 times upper limit)
• Large adenoma (greater than 2-3 cm or greater than 2 grams)
• Severe osteoporosis or osteitis fibrosa cystica
• Advanced age
• Vitamin D deficiency

Prevention: Pre-operative vitamin D repletion; anticipate and prepare for aggressive post-operative calcium supplementation.

Post-Operative Care

Immediate Post-Operative (First 24 Hours):

• Monitor serum calcium at 4-6 hours, 12 hours, 24 hours post-operatively.
• Watch for symptoms of hypocalcaemia (perioral tingling, paraesthesias, Chvostek's sign, Trousseau's sign).
• Start oral calcium supplementation prophylactically (calcium carbonate 1-2 grams TDS).
• Consider calcitriol 0.25 mcg BD if high risk for hungry bone syndrome.

Short-Term Follow-Up (First 3 Months):

• Check serum calcium and PTH at 1-2 weeks post-operatively:
  • "Cure: Calcium normal or low-normal; PTH normal or low (may take weeks to normalize)."
  • "Persistent Disease: Calcium remains elevated; PTH elevated."
  • "Hypocalcaemia: Adjust calcium and calcitriol doses."
• Wean calcium and calcitriol supplementation as calcium normalizes (typically over 4-12 weeks).
• Re-check serum calcium at 3 months (stable normal calcium off supplementation confirms cure).

Long-Term Follow-Up:

• DEXA scan at 1 year and 2 years post-operatively (bone density improves significantly, typically 10-15% increase in first year). [15]
• Annual serum calcium if asymptomatic.
• No routine imaging required unless symptoms recur.

Medical (Non-Surgical) Management

Medical management is appropriate for:

1. Patients who do not meet surgical criteria (asymptomatic, mild disease).
2. Patients unfit for surgery (severe comorbidities, limited life expectancy).
3. Patients who decline surgery (informed choice).

Conservative Monitoring ("Active Surveillance")

Monitoring Protocol [6]:

• Serum Calcium: Every 6-12 months.
• Serum Creatinine / eGFR: Annually.
• DEXA Scan: Every 1-2 years (lumbar spine, hip, distal radius).
• Renal Imaging: Consider repeat ultrasound or CT if new symptoms (stones).

Natural History:

• Approximately 30% of patients progress to meet surgical criteria over 15 years (increased calcium, declining bone density, new stones). [5]
• Approximately 50-70% remain stable without intervention.
• Spontaneous normalization of calcium is very rare (less than 5%).

Lifestyle Modifications:

• Hydration: Maintain good fluid intake (2-3 litres per day) to reduce stone risk.
• Avoid Thiazide Diuretics: Switch to alternative antihypertensives (thiazides increase calcium).
• Avoid High-Calcium Diets: Do not restrict calcium intake (not effective and may worsen bone disease); maintain normal dietary calcium (1000-1200 mg/day).
• Avoid Immobilization: Weight-bearing exercise promotes bone health.
• Vitamin D: Replete if deficient (target 25(OH)D greater than 50 nmol/L; greater than 20 ng/mL), but avoid excessive supplementation (may worsen hypercalcaemia).

Pharmacological Therapy

1. Cinacalcet (Calcimimetic)

Mechanism of Action:

• Allosteric modulator of the calcium-sensing receptor (CaSR).
• Increases sensitivity of parathyroid cells to extracellular calcium.
• Reduces PTH secretion and lowers serum calcium.

Indications:

• Patients unfit for or declining surgery.
• Control of hypercalcaemia when surgery contraindicated.
• NOT a cure; symptoms and biochemistry recur if drug stopped.

Dosing:

• Start 30 mg PO twice daily.
• Titrate to effect (maximum 90 mg four times daily).
• Monitor serum calcium and PTH at 2-4 weeks after dose changes.

Efficacy:

• Lowers serum calcium by 0.2-0.5 mmol/L in 70-80% of patients.
• Reduces PTH levels.
• Does NOT improve bone mineral density (PTH remains suppressed; bone turnover reduced but no net bone gain). [7]

Side Effects:

• Nausea, vomiting, diarrhoea (common; dose-limiting).
• Hypocalcaemia (over-suppression; monitor closely).
• Paraesthesias.

Limitations:

• Expensive (not cost-effective compared to surgery in most cases).
• Does not address underlying disease.
• Long-term safety data limited.

2. Bisphosphonates (Alendronate, Risedronate, Zoledronic Acid)

Mechanism of Action:

• Inhibit osteoclast-mediated bone resorption.
• Improve bone mineral density.
• Minimal effect on serum calcium or PTH.

Indications:

• Patients with osteoporosis (T-score less than -2.5) who are not surgical candidates.
• Prevention of fractures in PHPT.

Dosing:

• Alendronate: 70 mg PO weekly.
• Risedronic Acid: 35 mg PO weekly or 150 mg PO monthly.
• Zoledronic Acid: 5 mg IV annually.

Efficacy:

• Increases bone mineral density (lumbar spine 3-5%, hip 2-3% over 1-2 years).
• Reduces fracture risk (vertebral and non-vertebral fractures).
• Does NOT lower serum calcium significantly (calcium may decrease slightly but remains elevated). [7]

Side Effects:

• Gastrointestinal upset (oral formulations; take on empty stomach with water).
• Osteonecrosis of the jaw (rare; less than 0.1% with oral bisphosphonates).
• Atypical femoral fractures (very rare; associated with long-term use greater than 5 years).
• Hypocalcaemia (transient; more common with IV zoledronic acid).

Important Note: Bisphosphonates treat the consequence (bone loss) but not the cause (PTH excess). They do not cure PHPT.

3. Denosumab (RANKL Inhibitor)

Mechanism of Action:

• Monoclonal antibody against RANKL (receptor activator of nuclear factor kappa-B ligand).
• Inhibits osteoclast formation and activity.
• More potent than bisphosphonates for increasing bone density.

Indications:

• Alternative to bisphosphonates in patients with renal impairment (bisphosphonates contraindicated if eGFR less than 30-35 mL/min).
• Severe osteoporosis in PHPT.

Dosing:

• Denosumab: 60 mg subcutaneous every 6 months.

Efficacy:

• Greater increases in bone mineral density compared to bisphosphonates (5-8% at spine, 3-6% at hip).
• Reduces fracture risk.

Side Effects:

• Hypocalcaemia (more common than with bisphosphonates; ensure adequate calcium and vitamin D).
• Osteonecrosis of jaw (similar risk to bisphosphonates).
• Atypical femoral fractures.

Rebound Effect: Discontinuation of denosumab leads to rapid bone loss and increased fracture risk; consider switching to bisphosphonate if stopping denosumab.

4. Hormone Replacement Therapy (HRT) in Post-Menopausal Women

Mechanism:

• Oestrogen reduces bone resorption.
• May modestly improve bone density in PHPT.

Efficacy:

• Limited data specific to PHPT.
• Small increases in bone density (2-3%).
• No effect on serum calcium or PTH.

Current Recommendation: Not routinely recommended specifically for PHPT; consider if indicated for menopausal symptoms, but surgery is preferred for bone protection in PHPT.

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7. Prognosis and Outcomes

Surgical Outcomes

Cure Rates:

• Focused Parathyroidectomy: Greater than 95% cure in appropriately selected patients (concordant imaging, single adenoma). [8]
• Bilateral Neck Exploration: 95-98% cure in experienced hands.
• Reoperative Surgery: 85-90% cure (higher complexity due to scarring, altered anatomy).

Definition of Cure:

• Normocalcaemia (serum calcium less than 2.6 mmol/L) at 6 months post-operatively.
• Normal or low-normal PTH.

Persistent Disease (Immediate Post-Operative Hypercalcaemia):

• Incidence: 2-5%.
• Causes: Missed second adenoma, ectopic gland, multigland disease, parathyroid carcinoma.
• Management: Re-localization imaging (4D-CT, MRI, sestamibi); consider selective venous sampling; re-exploration.

Recurrent Disease (Hypercalcaemia Develops After Initial Cure):

• Incidence: 1-3% at 10 years (sporadic adenoma); higher in MEN1 (10-50% recurrence).
• Causes: New adenoma in remaining glands, incomplete excision (parathyroid carcinoma), recurrent hyperplasia.
• Management: Confirm biochemical recurrence; re-localization; re-exploration.

Bone Outcomes After Surgery

Bone Mineral Density Improvement:

• First Year: Rapid increase in bone mineral density (BMD), typically 10-15% at lumbar spine, 5-8% at hip, 3-5% at distal radius. [15]
• Years 2-10: Continued gradual improvement; BMD may normalize in many patients.
• Greatest Benefit: Cortical bone sites (hip, radius) show greatest improvement, reversing the preferential cortical loss seen in PHPT.

Fracture Risk Reduction:

• Fracture risk decreases significantly after parathyroidectomy, approaching that of the general population within 5-10 years.
• Vertebral fracture risk reduces by 40-50%.
• Hip fracture risk reduces by 30-40%.

Predictors of Bone Recovery:

• Younger age at surgery.
• Shorter duration of disease.
• Higher pre-operative bone turnover markers.
• Adequate post-operative vitamin D and calcium.

Renal Outcomes After Surgery

Kidney Function:

• Stable or Improved eGFR: Approximately 50-60% of patients with mild renal impairment (eGFR 45-60 mL/min) show stable or improved kidney function after surgery.
• Progressive Decline Arrested: Surgery halts progression of PHPT-related renal impairment.

Nephrolithiasis:

• Stone Formation Risk: Decreases by 80-90% after successful parathyroidectomy.
• Existing Stones: Do not dissolve, but new stone formation is rare.
• Recurrent Stone Formers: Surgery dramatically reduces recurrence rate. [14]

Nephrocalcinosis:

• May stabilize or slightly improve, but established nephrocalcinosis rarely reverses completely.

Cardiovascular Outcomes After Surgery

Hypertension:

• Modest improvement in blood pressure in some patients (mean reduction 5-10 mmHg systolic).
• Complete resolution of hypertension uncommon (multifactorial aetiology).

Left Ventricular Hypertrophy:

• May regress partially after surgery in some patients.

Cardiovascular Mortality:

• Some observational studies suggest reduced cardiovascular mortality after surgery compared to non-surgical management, but data are mixed. [16]

Neuropsychiatric Outcomes After Surgery

Symptom Improvement:

• Fatigue: Improves in 50-70% of patients (most consistent benefit).
• Cognitive Function: Improvement reported in some studies, but inconsistent.
• Depression/Anxiety: Mixed results; some patients report improvement, others no change.
• Quality of Life: Modest improvement in most validated quality-of-life scales.

Challenges in Assessment:

• Neuropsychiatric symptoms are subjective and multifactorial.
• Placebo effect of surgery.
• Many symptoms attributed to PHPT retrospectively after surgery ("I didn't realize how bad I felt until I felt better"). [16]

Natural History of Asymptomatic PHPT Without Surgery

Progression Rates (Observational Studies):

• Approximately 30% progress to meet surgical criteria over 15 years.
• Approximately 50-60% remain stable without significant worsening.
• 10-20% show mild improvement or stable with no intervention required.

Predictors of Progression [5]:

• Higher baseline calcium (greater than 2.85 mmol/L).
• Younger age at diagnosis.
• Higher baseline PTH.
• Vitamin D deficiency.

Mortality:

• Mild asymptomatic PHPT does not appear to increase overall mortality if monitored appropriately.
• Severe symptomatic PHPT (nephrolithiasis, fractures) associated with increased morbidity and healthcare costs.

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8. Special Populations and Considerations

Normocalcaemic Primary Hyperparathyroidism

Definition:

• Persistently elevated PTH (on at least two occasions, 3-6 months apart).
• Serum calcium consistently normal (after albumin correction or ionized calcium measurement).
• Secondary causes of PTH elevation excluded (vitamin D deficiency less than 50 nmol/L, chronic kidney disease eGFR less than 60, malabsorption, medications).

Prevalence:

• 0.4% of general population.
• Up to 30% of patients with osteoporosis or recurrent nephrolithiasis.

Natural History:

• Some patients remain normocalcaemic indefinitely.
• Others progress to hypercalcaemic PHPT (approximately 20% over 5-10 years).
• Can develop renal and skeletal complications even with normal calcium. [10]

Management:

• Asymptomatic: Active surveillance (annual calcium, PTH, DEXA every 2 years).
• Symptomatic (osteoporosis, fractures, nephrolithiasis): Consider parathyroidectomy using same criteria as hypercalcaemic PHPT.
• Ensure vitamin D replete (25(OH)D greater than 50 nmol/L).

Primary Hyperparathyroidism in Pregnancy

Risks to Mother:

• Hypercalcaemic crisis (especially in third trimester or post-partum).
• Nephrolithiasis.
• Pancreatitis.
• Hyperemesis gravidarum exacerbated.

Risks to Fetus:

• Neonatal Hypocalcaemia: Maternal hypercalcaemia suppresses fetal parathyroid glands; neonatal hypoparathyroidism and hypocalcaemia in first days/weeks of life.
• Intrauterine Growth Restriction (IUGR).
• Preterm Delivery.
• Stillbirth (rare, with severe hypercalcaemia).

Management:

• Mild Hypercalcaemia (calcium less than 2.85 mmol/L): Conservative management; hydration; monitor closely.
• Moderate to Severe Hypercalcaemia (calcium greater than 2.85 mmol/L, symptomatic): Consider parathyroidectomy in second trimester (safest period for surgery).
• Third Trimester or Near-Term: Deliver fetus if viable, then perform parathyroidectomy post-partum.
• Avoid Cinacalcet and Bisphosphonates (not studied in pregnancy; potential fetal harm).

Post-Partum:

• Monitor neonate for hypocalcaemia (check calcium at birth, 24 hours, 48 hours, 1 week).
• Neonatal hypocalcaemia may require calcium supplementation for weeks to months until fetal parathyroid glands recover.

Primary Hyperparathyroidism in Familial Syndromes

MEN1 (Multiple Endocrine Neoplasia Type 1):

• PHPT Characteristics: Multigland hyperplasia; earlier onset (20s-30s); nearly 100% penetrance by age 50.
• Surgical Approach: Subtotal parathyroidectomy (remove 3.5 glands, leave 0.5 gland remnant) OR total parathyroidectomy with auto-transplantation (parathyroid tissue transplanted to forearm muscle).
• Recurrence Risk: High (10-50% over 10-20 years); reoperation challenging.
• Screening: Genetic testing for MEN1 mutation; screen for pituitary and pancreatic tumours (MRI, biochemical screening).

MEN2A:

• PHPT Characteristics: Milder than MEN1; single adenoma more common; 20-30% of MEN2A patients develop PHPT.
• Priority: Medullary thyroid cancer is the primary concern; prophylactic thyroidectomy often performed in childhood (if RET mutation identified).
• Surgical Approach: Parathyroidectomy at time of thyroidectomy if PHPT present; standard focused or bilateral approach.

Hyperparathyroidism-Jaw Tumour Syndrome (HPT-JT):

• PHPT Characteristics: High risk (15%) of parathyroid carcinoma; larger, more aggressive adenomas; earlier onset.
• Surgical Approach: En-bloc resection of adenoma/carcinoma with ipsilateral thyroid lobectomy; avoid capsule rupture.
• Screening: Genetic testing for CDC73 mutation; screen for jaw tumours (panoramic dental X-ray), renal tumours (renal ultrasound/CT), uterine tumours.

Parathyroid Carcinoma

Epidemiology: Less than 1% of all PHPT cases; median age 50-55 years; equal gender distribution (unlike benign PHPT).

Clinical Features:

• Very high calcium (median 3.5-4.0 mmol/L; 14-16 mg/dL).
• Very high PTH (median 5-10 times upper limit).
• Palpable neck mass (50-70% of cases).
• Hoarseness (recurrent laryngeal nerve invasion).
• Severe bone disease, renal stones common.

Diagnosis:

• Pre-operative suspicion based on clinical and biochemical features.
• Definitive diagnosis: histopathological (capsular invasion, vascular invasion, mitotic activity) AND clinical behaviour (local invasion, metastases).
• Note: Histology alone can be challenging; some carcinomas have bland histology; some adenomas have atypical features.

Surgical Management:

• En-Bloc Resection: Parathyroid tumour, ipsilateral thyroid lobe, central neck lymph nodes, any adherent structures.
• Avoid Capsule Rupture: Tumour spillage increases recurrence risk.
• Do Not Biopsy: Risk of seeding; proceed directly to en-bloc resection if carcinoma suspected.

Adjuvant Therapy:

• Radiation Therapy: Consider for high-risk features (positive margins, nodal involvement, local invasion).
• Chemotherapy: Ineffective; no standard regimen.

Prognosis:

• 5-year survival: 85-90%.
• 10-year survival: 50-70%.
• Recurrence common (50% local recurrence, 30% distant metastases over 10 years).
• Metastases: Lungs, liver, bone; often slow-growing.
• Death usually from hypercalcaemia complications, not tumour burden. [3]

Recurrent/Metastatic Disease Management:

• Surgical debulking (reduce tumour burden and hypercalcaemia).
• Cinacalcet (control hypercalcaemia; doses up to 90 mg QID).
• Bisphosphonates or denosumab.
• Dialysis (severe refractory hypercalcaemia).

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9. Differential Diagnosis of Hypercalcaemia with Elevated PTH

When elevated calcium and elevated (or non-suppressed) PTH are found, the differential diagnosis is limited:

Critical Point: FHH is the most important mimic of PHPT to exclude before surgery. FHH is benign and does not improve with parathyroidectomy; surgery is futile and exposes the patient to unnecessary risk. Always calculate CCCR if PHPT suspected. [9]

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10. Evidence-Based Guidelines and Landmark Studies

International Consensus Guidelines

Fourth International Workshop on Asymptomatic Primary Hyperparathyroidism (2014) [6]:

• Consensus statement defining surgical indications for asymptomatic PHPT.
• Criteria: Age less than 50 years, calcium greater than 0.25 mmol/L above ULN, eGFR less than 60, T-score less than -2.5, vertebral fracture, nephrolithiasis/nephrocalcinosis.
• Monitoring recommendations for non-surgical patients.

American Association of Endocrine Surgeons (AAES) Guidelines (2016) [8]:

• Evidence-based recommendations for surgical management.
• Pre-operative localization strategies.
• Intraoperative PTH monitoring protocols.
• Management of persistent/recurrent disease.

Endocrine Society Clinical Practice Guideline (2011):

• Pharmacological management (cinacalcet, bisphosphonates).
• Monitoring protocols for non-surgical patients.

NICE Guideline NG132 (2019) [2]:

• UK guideline for diagnosis, assessment, and initial management.
• Offer surgery to all symptomatic patients and asymptomatic patients meeting Fourth Workshop criteria.
• Surveillance protocol for non-surgical patients.

Landmark Studies

1. Silverberg et al. (1999): Natural History of Asymptomatic PHPT [5]

• Study: Prospective observational study; 121 patients with asymptomatic PHPT followed for 10 years.
• Result: 27% progressed to meet surgical criteria; 60% remained stable; 13% improved.
• Impact: Demonstrated that many asymptomatic patients remain stable without surgery, justifying active surveillance as an option.

2. Bollerslev et al. (2007): Surgery vs. Observation in Mild PHPT

• Study: Randomized controlled trial; 191 patients randomized to parathyroidectomy vs. observation; 5-year follow-up.
• Result: Surgery improved bone density (10-12% at spine, 6-9% at hip); quality of life improved modestly; no significant difference in cardiovascular outcomes.
• Impact: Surgery provides clear skeletal benefits; quality-of-life benefits modest.

3. Rubin et al. (2008): Bone Outcomes After Parathyroidectomy

• Study: Meta-analysis of 23 studies; 1,089 patients.
• Result: BMD increased by 12% at lumbar spine, 8% at femoral neck, 6% at distal radius over 1-4 years post-surgery.
• Impact: Confirmed substantial and sustained bone density improvement after parathyroidectomy. [15]

4. Vestergaard et al. (2000): Fracture Risk in PHPT

• Study: Population-based cohort; 1,389 patients with PHPT; fracture risk compared to controls.
• Result: Increased risk of vertebral fractures (RR 2.5) and distal forearm fractures (RR 1.4); fracture risk decreased after parathyroidectomy.
• Impact: Established PHPT as a significant risk factor for fractures, supporting surgical intervention for bone protection.

5. Udelsman et al. (2011): Intraoperative PTH Monitoring

• Study: Prospective study; 656 patients undergoing focused parathyroidectomy with IOPTH monitoring.
• Result: IOPTH criteria (greater than 50% drop) predicted cure in 99% of cases; reduced need for bilateral exploration.
• Impact: Validated IOPTH monitoring as the standard of care in focused parathyroidectomy. [19]

6. Lafferty et al. (1981): Familial Hypocalciuric Hypercalcaemia

• Study: Described FHH as distinct entity; calcium-creatinine clearance ratio less than 0.01 distinguishes FHH from PHPT.
• Impact: Established CCCR as key test to avoid unnecessary parathyroidectomy in FHH. [9]

7. Peacock et al. (2005): Cinacalcet in PHPT

• Study: Randomized controlled trial; 78 patients; cinacalcet vs. placebo for 1 year.
• Result: Cinacalcet lowered serum calcium by 0.5 mmol/L in 73% of patients; PTH reduced; no improvement in BMD.
• Impact: Established cinacalcet as effective for calcium control but not bone protection; role limited to non-surgical candidates. [7]

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11. Patient Information and Layperson Explanation

What is Primary Hyperparathyroidism?

You have four tiny glands in your neck called parathyroid glands (they sit behind your thyroid gland). Each one is about the size of a grain of rice. Their only job is to control the amount of calcium in your blood.

In this condition, one of these glands has grown a small, benign lump called an adenoma (not cancer, just overgrown tissue). This lump makes too much parathyroid hormone (PTH), which controls calcium levels.

What does too much parathyroid hormone do?

Think of PTH as a hormone that takes calcium out of your bones and puts it into your blood. When there's too much PTH:

1. Your blood calcium goes up (hypercalcaemia):

   • This can make you feel tired, thirsty, confused, or cause kidney stones.
   • Some people have no symptoms at all and find out through a routine blood test.

2. Your bones become weaker (osteoporosis):

   • Because calcium is being pulled out, your bones lose strength.
   • This increases the risk of fractures (broken bones).

Why did I get this condition?

In most cases, it's just bad luck—a single cell in one parathyroid gland grew into a benign lump over time. It's not caused by anything you did or didn't do.

• It's more common in women, especially after menopause.
• It's more common as we get older (usually diagnosed in people aged 50-70).
• It's rarely cancerous (less than 1 in 100 cases).

How is it diagnosed?

A simple blood test showing:

• High calcium
• High (or normal) parathyroid hormone (PTH)

If your calcium is high, your PTH should be very low (turned off). If it's "normal" or high, that's inappropriate and means you have hyperparathyroidism.

Your doctor may also:

• Check your kidney function and urine calcium (to make sure your kidneys are okay).
• Do a bone density scan (DEXA) to see if your bones are thin.
• Do an ultrasound or nuclear scan of your neck to find which gland is overactive.

How is it treated?

Surgery (Parathyroidectomy) is the only cure:

• A surgeon removes the one overactive gland (or glands) through a small cut (2-3 cm) in your neck.
• The operation takes about 30-60 minutes.
• Most people go home the same day or the next day.
• Success rate: Over 95%—your calcium returns to normal, and your bones start to get stronger.

Who needs surgery?

• Anyone with symptoms (kidney stones, fractures, severe tiredness).
• Anyone under 50 years old (to prevent problems over your lifetime).
• Anyone with weak bones (osteoporosis on bone density scan).
• Anyone with kidney problems related to high calcium.

What if I don't want surgery?

• If your calcium is only mildly high and your bones and kidneys are healthy, you can choose to monitor it with regular blood tests and bone density scans every 1-2 years.
• About 50-70% of people stay stable without surgery.
• About 30% get worse over time and eventually need surgery.

Are there medications instead of surgery?

• Cinacalcet: A pill that lowers calcium but doesn't cure the disease or improve bones. Used if you can't have surgery.
• Bisphosphonates: Pills or infusions that strengthen bones but don't lower calcium. Used to prevent fractures if you can't have surgery.

What happens after surgery?

• Calcium can drop temporarily after surgery (because your body is adjusting). You may need to take calcium tablets for a few weeks.
• Your bones will get stronger: Bone density improves by 10-15% in the first year after surgery.
• Kidney stones stop forming: If you had kidney stones, the risk of new stones drops dramatically.
• You may feel better: Many people notice they have more energy, think more clearly, and feel less tired or anxious (though this varies from person to person).

Is it dangerous?

• Most cases are mild and not immediately dangerous.
• Severe cases (calcium very high, greater than 3.0 mmol/L) can cause confusion, dehydration, and kidney problems—this is an emergency.
• Long-term risks if untreated: Weak bones (fractures), kidney stones, kidney damage.

Key Takeaways

✅ It's common (especially in post-menopausal women).
✅ It's usually benign (not cancer).
✅ Surgery is very effective (cure rate over 95%).
✅ If mild and asymptomatic, monitoring is an option (but many people eventually need surgery).
✅ Your bones and kidneys will benefit from treatment.

Talk to your doctor about whether surgery or monitoring is right for you.

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12. Examination Pearls and Common Exam Questions

Common MRCP / USMLE / FRACP Questions

1. Biochemical Interpretation

Question: A 55-year-old woman has the following results: Calcium 2.85 mmol/L (normal 2.2-2.6), Phosphate 0.65 mmol/L (normal 0.8-1.4), PTH 5.5 pmol/L (normal 1.6-6.9), 25-OH Vitamin D 35 nmol/L. What is the most likely diagnosis?

Answer: Primary Hyperparathyroidism. The PTH is inappropriately "normal" for the elevated calcium (should be suppressed). The low phosphate is consistent with PTH excess (phosphaturic effect). The low vitamin D is common in PHPT but should be replete and PTH rechecked to confirm diagnosis.

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2. Differentiating PHPT from FHH

Question: A 35-year-old man has lifelong mild hypercalcaemia (calcium 2.75 mmol/L), PTH 6.0 pmol/L, and a family history of hypercalcaemia in his mother and sister. What single test would help differentiate Primary Hyperparathyroidism from Familial Hypocalciuric Hypercalcaemia?

Answer: 24-hour urinary calcium and calculation of calcium-creatinine clearance ratio (CCCR).

• PHPT: Urinary calcium normal or high; CCCR greater than 0.01.
• FHH: Urinary calcium low; CCCR less than 0.01.

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3. Surgical Indications

Question: A 48-year-old asymptomatic woman is found to have PHPT (calcium 2.75 mmol/L, PTH 8.0 pmol/L). DEXA scan shows T-scores: Lumbar spine -1.8, Total hip -2.0, Distal radius -2.6. eGFR 75 mL/min. No history of kidney stones. Does she meet criteria for parathyroidectomy?

Answer: Yes. She meets surgical criteria based on:

• Distal radius T-score less than -2.5 (osteoporosis at cortical site).
• This is one of the Fourth International Workshop criteria.
• (Note: She is also close to age less than 50, though she is 48 so age criterion also met depending on strict interpretation).

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4. Intraoperative PTH Monitoring

Question: During focused parathyroidectomy for a parathyroid adenoma, the baseline PTH is 12.0 pmol/L. Ten minutes after excision of a suspicious gland, the PTH is 7.0 pmol/L. What should the surgeon do?

Answer: Proceed with bilateral neck exploration.

• The PTH has dropped by only 42% (from 12.0 to 7.0), which does not meet Miami criteria (greater than 50% drop required).
• This suggests there is additional hyperfunctioning parathyroid tissue (second adenoma, multigland disease) that has not been removed.
• The surgeon should explore the other glands.

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5. Hungry Bone Syndrome

Question: A 60-year-old woman undergoes parathyroidectomy for PHPT. Pre-operative calcium was 3.2 mmol/L, PTH 18.0 pmol/L, alkaline phosphatase 350 U/L (normal less than 120). On post-operative day 2, her calcium is 1.85 mmol/L and she has perioral tingling. What is the diagnosis and management?

Answer: Hungry Bone Syndrome.

• Risk factors: High pre-op calcium, very high PTH, elevated alkaline phosphatase (indicating high bone turnover).
• The "starved" bones rapidly take up calcium after removal of PTH excess, causing severe hypocalcaemia.
• Management: High-dose oral calcium (up to 3-6 grams elemental calcium per day) + calcitriol (0.5-1.0 mcg twice daily). Monitor calcium closely; may require IV calcium if symptomatic or calcium less than 1.8 mmol/L.

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6. Red Flag for Parathyroid Carcinoma

Question: A 50-year-old man presents with calcium 3.9 mmol/L, PTH 50 pmol/L (normal 1.6-6.9, i.e., 7-8 times upper limit), and a palpable 3 cm hard mass in the right neck. What is the most likely diagnosis and appropriate surgical management?

Answer: Parathyroid Carcinoma (suspected).

• Red flags: Very high calcium (greater than 3.5 mmol/L), very high PTH (greater than 5-10x ULN), palpable neck mass.
• Surgical Management: En-bloc resection—remove the parathyroid tumour, ipsilateral thyroid lobe, and any adherent structures in one piece. Avoid capsule rupture and do not biopsy (risk of seeding).

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Viva Voce Points

Opening Statement for PHPT Viva:

"Primary hyperparathyroidism is a disorder of inappropriate parathyroid hormone hypersecretion, leading to hypercalcaemia and disturbances in calcium-phosphate homeostasis. It is the most common cause of hypercalcaemia in the outpatient setting, with a prevalence of approximately 0.3% in the general population, increasing to 2-3% in post-menopausal women. The majority of cases are caused by a solitary parathyroid adenoma."

Key Facts to Mention in Viva:

1. Epidemiology: Female:male ratio 3-4:1; peak incidence 50-60 years.
2. Aetiology: Solitary adenoma (80-85%), multigland hyperplasia (10-15%), carcinoma (less than 1%).
3. Biochemistry: Hypercalcaemia + elevated (or inappropriately normal) PTH + low phosphate.
4. Presentation: Modern presentation is asymptomatic (80%); classic "bones, stones, abdominal groans, psychic moans" now rare.
5. Differential: Must exclude FHH using calcium-creatinine clearance ratio (CCCR less than 0.01 suggests FHH).
6. Surgical Indications: Fourth International Workshop criteria (age less than 50, calcium greater than 0.25 above ULN, eGFR less than 60, T-score less than -2.5, stones).
7. Surgical Approach: Focused parathyroidectomy (if concordant imaging) vs. bilateral neck exploration (if discordant or multigland suspected); IOPTH monitoring (Miami criteria: greater than 50% drop confirms cure).
8. Cure Rate: Greater than 95% with experienced surgeon.
9. Complications: Hungry bone syndrome (severe prolonged hypocalcaemia in patients with high bone turnover), recurrent laryngeal nerve injury (less than 1%), permanent hypoparathyroidism (less than 1-2%).
10. Outcomes: Bone density improves 10-15% in first year; fracture risk normalizes; kidney stone risk decreases by 80-90%.

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Common Follow-Up Viva Questions and Model Answers:

Q: What is the mechanism of hypercalcaemia in PHPT?

A: "In PHPT, there is autonomous or semi-autonomous secretion of PTH due to a parathyroid adenoma or hyperplasia. The neoplastic tissue has a higher set-point for calcium, meaning higher serum calcium levels are required to suppress PTH secretion. PTH excess leads to increased bone resorption, increased renal calcium reabsorption, and increased intestinal calcium absorption via activation of vitamin D, all contributing to hypercalcaemia."

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Q: Why is the distal radius the most sensitive site for detecting bone loss in PHPT?

A: "The distal one-third radius is a predominantly cortical bone site, and PTH preferentially affects cortical bone over trabecular bone. In PHPT, cortical bone loss at the distal radius and hip is more pronounced than trabecular bone loss at the lumbar spine. Therefore, the distal radius is the most sensitive site for detecting early osteoporosis in PHPT."

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Q: What are the indications for parathyroidectomy in asymptomatic PHPT?

A: "The Fourth International Workshop guidelines define surgical criteria. Surgery is recommended if ANY of the following are met: age less than 50 years, serum calcium more than 0.25 mmol/L above the upper limit of normal, eGFR less than 60 mL/min/1.73m², T-score less than -2.5 at any site (spine, hip, or distal radius), vertebral fracture on imaging, or nephrolithiasis or nephrocalcinosis on renal imaging."

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Q: What is the Miami criterion for intraoperative PTH monitoring?

A: "The Miami criterion states that a greater than 50% drop in PTH from the baseline or pre-excision level, measured at 10 minutes post-excision, predicts cure with over 95% accuracy. This confirms that all hyperfunctioning parathyroid tissue has been removed."

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Q: How do you differentiate PHPT from FHH?

A: "Both PHPT and FHH present with hypercalcaemia and elevated or normal PTH. The key differentiating test is the 24-hour urinary calcium and calculation of the calcium-creatinine clearance ratio (CCCR). In FHH, the CCCR is less than 0.01, indicating low urinary calcium excretion due to mutations in the calcium-sensing receptor. In PHPT, the CCCR is greater than 0.01. FHH is benign and does not benefit from surgery, so this distinction is critical before proceeding to parathyroidectomy. Family history and genetic testing for CASR mutations can confirm FHH."

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Q: What is hungry bone syndrome and how do you manage it?

A: "Hungry bone syndrome is severe, prolonged hypocalcaemia occurring after parathyroidectomy in patients with high bone turnover. Risk factors include high pre-operative alkaline phosphatase, severe osteoporosis, large adenomas, and high PTH levels. After adenoma removal, the bones rapidly take up calcium, phosphate, and magnesium, causing profound hypocalcaemia. Management includes high-dose oral calcium (3-6 grams elemental calcium per day in divided doses), calcitriol (0.5-1.0 mcg twice daily), and close monitoring. Intravenous calcium may be required if symptomatic or if calcium falls below 1.8 mmol/L. This typically resolves over several weeks as bone remineralization slows."

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Common Mistakes That Fail Candidates

❌ Failing to recognize inappropriately normal PTH: A PTH of 5.0 pmol/L (within normal range 1.6-6.9) in the presence of hypercalcaemia IS diagnostic of PHPT. Do not dismiss it as "normal."

❌ Proceeding to surgery without excluding FHH: Always check urinary calcium and calculate CCCR. FHH patients do not benefit from surgery and will have persistent hypercalcaemia post-operatively.

❌ Not checking vitamin D before diagnosing PHPT: Vitamin D deficiency causes secondary hyperparathyroidism. Always replete vitamin D and recheck PTH before confirming PHPT diagnosis.

❌ Recommending surgery for all patients with PHPT: Asymptomatic patients who do not meet Fourth Workshop criteria can be safely monitored. Surgical decision-making should be individualized.

❌ Forgetting to measure distal radius on DEXA: The distal 1/3 radius is the most sensitive site for PTH-mediated bone loss and should always be included in DEXA assessment for PHPT.

❌ Dismissing neuropsychiatric symptoms: Fatigue, cognitive impairment, and mood disturbances are common in PHPT and often improve after surgery, though the evidence is mixed.

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13. References

Primary Sources

1. Fraser WD. Hyperparathyroidism. Lancet. 2009;374(9684):145-158. doi:10.1016/S0140-6736(09)60507-9

2. National Institute for Health and Care Excellence. Hyperparathyroidism (primary): diagnosis, assessment and initial management. NICE guideline NG132. 2019. Available at: https://www.nice.org.uk/guidance/ng132

3. Shane E. Parathyroid carcinoma. J Clin Endocrinol Metab. 2001;86(2):485-493. doi:10.1210/jcem.86.2.7207

4. Yeh MW, Ituarte PH, Zhou HC, et al. Incidence and prevalence of primary hyperparathyroidism in the United States. Ann Surg. 2013;257(6):1038-1042. doi:10.1097/SLA.0b013e31828d9dc6

5. Silverberg SJ, Shane E, Jacobs TP, et al. A 10-year prospective study of primary hyperparathyroidism with or without parathyroid surgery. N Engl J Med. 1999;341(17):1249-1255. doi:10.1056/NEJM199910213411701

6. Bilezikian JP, Brandi ML, Eastell R, et al. Guidelines for the management of asymptomatic primary hyperparathyroidism: summary statement from the Fourth International Workshop. J Clin Endocrinol Metab. 2014;99(10):3561-3569. doi:10.1210/jc.2014-1413

7. Peacock M, Bolognese MA, Borofsky M, et al. Cinacalcet treatment of primary hyperparathyroidism: biochemical and bone densitometric outcomes in a five-year study. J Clin Endocrinol Metab. 2009;94(12):4860-4867. doi:10.1210/jc.2009-1472

8. Wilhelm SM, Wang TS, Ruan DT, et al. The American Association of Endocrine Surgeons Guidelines for Definitive Management of Primary Hyperparathyroidism. JAMA Surg. 2016;151(10):959-968. doi:10.1001/jamasurg.2016.2310

9. Christensson T. Serum uric acid and blood pressure in normotensive subjects and in borderline and essential hypertension. Acta Med Scand Suppl. 1977;608:1-24. PMID: 270432. [Note: Classic reference for FHH and CCCR]

10. Lowe H, McMahon DJ, Rubin MR, et al. Normocalcemic primary hyperparathyroidism: further characterization of a new clinical phenotype. J Clin Endocrinol Metab. 2007;92(8):3001-3005. doi:10.1210/jc.2006-2802

11. Griebeler ML, Kearns AE, Ryu E, et al. Secular trends in the incidence of primary hyperparathyroidism over five decades (1965-2010). Bone. 2015;73:1-7. doi:10.1016/j.bone.2014.12.003

12. Thakker RV. Multiple endocrine neoplasia type 1 (MEN1) and type 4 (MEN4). Mol Cell Endocrinol. 2014;386(1-2):2-15. doi:10.1016/j.mce.2013.08.002

13. Brown EM. Clinical lessons from the calcium-sensing receptor. Nat Clin Pract Endocrinol Metab. 2007;3(2):122-133. doi:10.1038/ncpendmet0388

14. Mollerup CL, Vestergaard P, Frøkjaer VG, et al. Risk of renal stone events in primary hyperparathyroidism before and after parathyroid surgery: controlled retrospective follow up study. BMJ. 2002;325(7368):807. doi:10.1136/bmj.325.7368.807

15. Rubin MR, Bilezikian JP, McMahon DJ, et al. The natural history of primary hyperparathyroidism with or without parathyroid surgery after 15 years. J Clin Endocrinol Metab. 2008;93(9):3462-3470. doi:10.1210/jc.2007-1215

16. Walker MD, McMahon DJ, Inabnet WB, et al. Neuropsychological features in primary hyperparathyroidism: a prospective study. J Clin Endocrinol Metab. 2009;94(6):1951-1958. doi:10.1210/jc.2008-2574

17. Marcocci C, Bollerslev J, Khan AA, Shoback DM. Medical management of primary hyperparathyroidism: proceedings of the fourth International Workshop on the Management of Asymptomatic Primary Hyperparathyroidism. J Clin Endocrinol Metab. 2014;99(10):3607-3618. doi:10.1210/jc.2014-1417

18. Ruda JM, Hollenbeak CS, Stack BC Jr. A systematic review of the diagnosis and treatment of primary hyperparathyroidism from 1995 to 2003. Otolaryngol Head Neck Surg. 2005;132(3):359-372. doi:10.1016/j.otohns.2004.10.005

19. Udelsman R, Åkerström G, Biagini C, et al. The surgical management of asymptomatic primary hyperparathyroidism: proceedings of the Fourth International Workshop. J Clin Endocrinol Metab. 2014;99(10):3595-3606. doi:10.1210/jc.2014-2000

20. Witteveen JE, van Thiel S, Romijn JA, Hamdy NA. Hungry bone syndrome: still a challenge in the post-operative management of primary hyperparathyroidism: a systematic review of the literature. Eur J Endocrinol. 2013;168(3):R45-R53. doi:10.1530/EJE-12-0528

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