Definition
- Precocious puberty is the appearance of secondary sexual characteristics before 8 years in girls and before 9 years in boys.
- It is classified by whether the hypothalamic-pituitary-gonadal (HPG) axis is activated.
Classification
| Type | Mechanism | Common causes |
|---|
| Central (true, GnRH-dependent) | Early activation of the HPG axis | Idiopathic (commonest in girls), CNS lesions/tumours, post-infection/irradiation |
| Peripheral (pseudo, GnRH-independent) | Sex steroids from outside the axis | CAH, adrenal/gonadal tumours, McCune-Albright syndrome, exogenous steroids, hCG-secreting tumours |
Normal Variants (to Recognise and Reassure)
- Premature thelarche — isolated early breast development, no other progression.
- Premature adrenarche — early pubic/axillary hair without other pubertal signs.
- These are usually benign and non-progressive.
Clinical Evaluation
- History and Tanner staging; documentation of the sequence and tempo of changes.
- Growth assessment and bone age (typically advanced in true precocity).
- Look for CNS symptoms (headache, visual changes), café-au-lait macules (McCune-Albright/NF1), and virilising features.
Investigations
- GnRH (LHRH) stimulation test — a pubertal LH response indicates central precocity.
- Basal LH/FSH, oestradiol/testosterone; 17-OHP and adrenal androgens (for CAH/adrenal cause).
- MRI brain (central, especially boys and young girls) and pelvic/adrenal ultrasound; thyroid function; bone-age X-ray.
Management
- Central precocious puberty — GnRH analogues (e.g. Leuprolide) to halt progression and preserve final height; treat any underlying CNS cause.
- Peripheral precocious puberty — treat the specific cause (surgery for tumours, glucocorticoids for CAH, specific agents for McCune-Albright).
- Psychological support for the child and family.
Normal Pubertal Sequence (for Reference)
- Girls: thelarche (breast) → pubarche → growth spurt → menarche.
- Boys: testicular enlargement (first sign, > 4 mL) → pubarche → penile growth → growth spurt.
Consequences of Untreated Precocity
- Early rapid growth but premature epiphyseal fusion → short final adult height.
- Psychosocial/behavioural difficulties from a body-mind mismatch.
Mccune-albright Syndrome
A cause of peripheral precocious puberty featuring the triad of polyostotic fibrous dysplasia, café-au-lait macules (irregular 'coast of Maine' borders) and autonomous endocrine hyperfunction (precocious puberty).
Investigation Summary
| Test | Purpose |
|---|
| Bone age | Advanced in true precocity |
| GnRH stimulation | Pubertal LH → central |
| MRI brain | CNS cause (esp. Boys) |
| 17-OHP / androgens | CAH / adrenal cause |
| Pelvic/adrenal USG | Cyst/tumour |
Premature Thelarche VS True Precocity
| Feature | Premature thelarche | True precocious puberty |
|---|
| Other pubertal signs | Absent | Present (pubarche, growth spurt) |
| Growth velocity | Normal | Accelerated |
| Bone age | Normal | Advanced |
| Progression | None/regresses | Progressive |
Prognosis
- Treated central precocious puberty (GnRH analogues) halts progression and protects final adult height; outcome in peripheral precocity depends on the underlying cause.
- Psychological support helps the child cope with being physically out of step with peers.