Precocious Puberty
The onset of puberty before age 8 in girls or 9 in boys due to early HPG axis activation. GnRH agonists (histrelin implant, leuprolide depot, triptorelin) suppress premature sex hormone production through receptor downregulation, pausing puberty until an appropriate age.
Technical Context
Central precocious puberty (CPP) results from premature activation of hypothalamic GnRH neurons → pulsatile GnRH → LH/FSH → sex steroid production → premature secondary sexual characteristics and accelerated bone maturation. Diagnosis: pubertal development before age 8 (girls) or 9 (boys), elevated basal or GnRH-stimulated LH levels, advanced bone age on hand X-ray. GnRH agonist therapy: histrelin implant (Supprelin LA — 12-month SC implant, most convenient), leuprolide depot (1-month or 3-month IM injection), or triptorelin depot (every 28 days). Mechanism: continuous GnRH → initial LH/FSH surge (1-2 weeks) → GnRH receptor downregulation → gonadotropin suppression → sex steroid levels fall to prepubertal range. Treatment is continued until an appropriate age for puberty (typically age 11-12 for girls, 12-13 for boys), then discontinued to allow natural pubertal progression. Monitoring: LH suppression, height velocity, bone age.