gonadarche

Gonadarche is the true ignition of puberty: the moment the ovaries or testes wake up and begin producing sex hormones in earnest. If adrenarche is a quiet prelude, gonadarche is the main engine starting.

It begins in the brain, not the gonads. Through childhood the hypothalamus keeps its GnRH pulses suppressed; at gonadarche these pulses resume, at first mainly during sleep, and grow stronger and more frequent. The pituitary answers with rising LH and FSH, which stimulate the gonads to mature follicles and make estradiol, or to enlarge and produce testosterone.

The visible result of gonadarche is what most people picture as puberty: breast development and eventually menstruation in girls, testicular enlargement and deepening voice in boys, plus the major growth spurt powered by the interplay of sex steroids and growth hormone.

A subtle point worth keeping straight is that gonadarche and adrenarche are separate switches with separate controls. A child can show early adrenarche without gonadarche, and the medical concern of true precocious or delayed puberty is specifically about the timing of gonadarche, not the adrenal androgens.