Normal puberty and adolescent development — branching viva

Stem

The examiner will test whether you understand normal puberty well enough to stage it, distinguish normal variants from pathology, and defend your referral decisions. [1] [2]

Branch 1 — Physiology

Examiner: What switches puberty on? [7]

Strong answer: Throughout childhood the GnRH pulse generator is actively suppressed. At puberty, kisspeptin neurons in the hypothalamus (the KNDy population) release that brake, and GnRH pulses resume — first at night, then through the day. The pulses drive pituitary LH and FSH, which act on the gonads to produce estrogen or testosterone. Energy-balance signals such as leptin and insulin modulate the kisspeptin pathway, which is why body fat and nutrition influence timing. [7]

Examiner: What is adrenarche, and is it the same process? [7]

Strong answer: No. Adrenarche is the separate maturation of the adrenal zona reticularis, producing DHEA-S that drives pubic and axillary hair. It is independent of the HPG axis, which is why pubic hair and breast or testicular development can appear at different times and must be staged separately. [7] [8]

Branch 2 — Staging and sequence

Examiner: What is the first sign of puberty in girls and in boys? [1] [2]

Strong answer: In girls, breast budding — thelarche, B2 — is usually first. In boys, testicular enlargement to at least 4 mL (G2) is always first. Pubic hair is not the first sign in either sex; it reflects adrenarche. [1] [2]

Examiner: Give the normal sequence and timing in girls. [1]

Strong answer: Thelarche first (8 to 13 years), then adrenarche-driven pubic hair, then the growth spurt with peak height velocity around 11.5 to 12 years, and finally menarche (10 to 15 years), roughly two to two-and-a-half years after thelarche. [1]

Examiner: Why stage breast and pubic hair separately? [8]

Strong answer: Because gonadarche and adrenarche are independent. A girl at B3 with PH1 is normal — the breast is responding to estrogen before the adrenal has switched on. The reverse, PH3 with B1, raises the question of an androgen source. [8]

Branch 3 — Normal variants

Examiner: A 4-year-old girl has an isolated breast bud, no growth acceleration, prepubertal gonadotropins. What is this and what do you do? [8]

Strong answer: Premature thelarche — a benign normal variant. Reassure and monitor growth and stage every 6 to 12 months for progression to true central puberty. No hormonal panel, ultrasound or MRI is needed for this presentation. [8]

Examiner: A 7-year-old has isolated pubic hair with normal bone age and growth velocity. [8]

Strong answer: Premature adrenarche. Exclude non-classic congenital adrenal hyperplasia with a 17-hydroxyprogesterone, then reassure and surveil — it flags later metabolic and polycystic ovary syndrome risk worth naming to the family. [8]

Branch 4 — Precocious puberty

Examiner: A 7-year-old girl: progressive breast development, height velocity 9 cm per year, bone age advanced 3 years, pubertal-range LH. What is this and what next? [3] [5]

Strong answer: Central precocious puberty, rapidly progressive, with risk of premature epiphyseal fusion and reduced adult height. Confirm with a GnRH- or agonist-stimulation test, and refer to paediatric endocrinology for consideration of GnRH-analogue suppression. [3] [5]

Examiner: Who gets a brain MRI? [5]

Strong answer: All boys with central precocious puberty (higher yield of a CNS cause). Girls under 6 years, and any child with neurological signs. Girls 6 to 8 years with isolated, slowly progressive central precocious puberty may be managed without immediate imaging — but this girl's rapid progression warrants full evaluation. [5]

Branch 5 — Delayed puberty

Examiner: A 14-year-old boy, testes 3 mL, father a late bloomer, bone age 2 years behind, normal velocity. Diagnosis? [4] [6]

Strong answer: Constitutional delay of growth and puberty — the most common cause of delayed puberty in boys (over 60 per cent). The triad is family history, delayed bone age equal to height age, and normal growth velocity with the child short for the family. [4] [6]

Examiner: How do you distinguish it from permanent hypogonadism? [6]

Strong answer: By the pattern: constitutional delay has the family history and the matched delayed bone age with normal velocity. Permanent hypogonadotropic hypogonadism (such as Kallmann syndrome with anosmia) or hypergonadotropic hypogonadism (gonadal failure) lacks that pattern and may have other features. The distinction can take follow-up to declare itself — borderline cases are referred, not dismissed. [6]

Examiner extras

• Growth ceases about two to two-and-a-half years after menarche — a key adult-height predictor. [1]
• Physiologic gynaecomastia is normal in about half of boys at G3 to G4. [8]
• Irregular cycles are the norm for one to two years post-menarche. [8]
• Peak height velocity: girls about 8 cm per year at 11.5 to 12 years; boys about 9 to 10 cm per year at 13.5 to 14 years. [1]
• The adolescent brain matures reward circuitry before cognitive control — the biology of adolescent risk-taking. [1]