GPAtlas🧭 When to suspect
Puberty is delayed when the first physical signs have not appeared by an age roughly two standard deviations beyond the population mean. In practice this means no breast development by age 13 in girls, and no testicular enlargement (volume below 4 mL) by age 14 in boys. In girls, persisting primary amenorrhoea by 15 despite otherwise normal breast development also warrants assessment. Delayed puberty affects around 2% of adolescents and is commoner in boys.
The first sign of true puberty is breast budding (thelarche) in girls and testicular enlargement in boys. The appearance of pubic or axillary hair (adrenarche) is driven by adrenal androgens and is not evidence that true puberty has begun. Most young people actually present worried about short stature or slow growth rather than the pubertal delay itself, so growth must be assessed in every case.
By far the commonest cause is constitutional delay of growth and puberty (CDGP) – a benign, self-limiting variant with a strong family history – but it remains a diagnosis of exclusion. The most useful way to frame any case is to separate the three broad categories by their gonadotrophin (LH/FSH) pattern.
| Category | LH / FSH | Typical causes |
|---|---|---|
| Constitutional delay (CDGP) | Low / normal (delayed but intact axis) | Familial “late development”; the commonest cause, especially in boys; bone age delayed; excellent prognosis |
| Hypogonadotrophic hypogonadism | Low / normal | Functional – chronic illness (coeliac, IBD, hypothyroidism), undernutrition, eating disorders, excessive exercise. Organic – Kallmann syndrome (with anosmia), idiopathic hypogonadotrophic hypogonadism, pituitary/hypothalamic tumour, cranial irradiation |
| Hypergonadotrophic hypogonadism | High | Primary gonadal failure – Turner syndrome (girls), Klinefelter syndrome (boys), chemotherapy/radiotherapy, gonadal damage or torsion |
Source: BSPED · RCPCH
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