Introduction
This topic joins two subjects: puberty, the change from child to adult body, and the control of calcium and phosphate, whose failure in a growing child causes rickets.
Normal puberty
The hypothalamus restarts pulsatile GnRH release (switched on by kisspeptin) → the pituitary releases LH and FSH → the gonads make oestradiol or testosterone and gametes. Separately, the adrenals make more androgens from about 6–8 years (adrenarche): pubic and axillary hair, body odour, acne.
Tanner stages 1 to 5 describe breast (girls), genitals (boys) and pubic hair. The orchidometer measures testicular volume.
Precocious puberty
Signs of puberty before 8 years in girls or 9 years in boys.
- Tests: growth velocity, bone age (advanced), LH/FSH and sex steroids, GnRH stimulation test, pelvic ultrasound, MRI.
- Treatment of central puberty: GnRH agonists (leuprorelin, triptorelin) to protect final height and for emotional reasons; treat the cause.
Delayed puberty
No breast development by 13 years in girls or testes under 4 mL by 14 years in boys (or no menarche by 15).
- Constitutional delay (commonest, mostly boys; family history; delayed bone age; catches up).
- Low gonadotrophins (hypogonadotropic): chronic illness, undernutrition, anorexia, intense sport, hypothyroidism, Kallmann syndrome (with loss of smell), pituitary tumours (craniopharyngioma).
- High gonadotrophins (gonadal failure): Turner syndrome, Klinefelter syndrome, chemotherapy or radiotherapy.
- Treatment: short courses of low-dose testosterone or oestrogen; treat the cause.