Gonadarche

Gonadarche is the earliest stage of puberty involving the maturation of the gonads (ovaries in females and testes in males). This maturation is triggered by the reactivation of the hypothalamic-pituitary-gonadal (HPG) axis, leading to increased secretion of sex hormones.

In both sexes, gonadarche is initiated by the pulsatile release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. GnRH stimulates the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These gonadotropins then act on the gonads, causing them to enlarge and begin producing sex hormones.

In females, FSH stimulates the ovaries to produce estrogen, leading to the development of secondary sexual characteristics such as breast development (thelarche), the growth spurt, and the onset of menstruation (menarche). LH also plays a role in ovarian function and ovulation.

In males, LH stimulates the Leydig cells in the testes to produce testosterone. FSH stimulates the Sertoli cells, which are crucial for spermatogenesis. The increase in testosterone leads to the development of secondary sexual characteristics such as deepening of the voice, growth of facial and body hair, muscle development, and testicular and penile enlargement.

Gonadarche is distinct from adrenarche, which is the increase in adrenal androgen production that typically occurs before gonadarche. While both are part of puberty, they are controlled by separate mechanisms. Adrenarche is primarily driven by increased secretion of adrenal androgens like dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S).

The timing of gonadarche varies among individuals, but it generally begins between the ages of 8 and 13 in girls and 9 and 14 in boys. Premature gonadarche (precocious puberty) is defined as the onset of gonadarche before the age of 8 in girls and 9 in boys. Delayed puberty is defined as the absence of signs of gonadarche by age 13 in girls and 14 in boys. Both premature and delayed puberty warrant medical evaluation.