Hypothalamic-pituitary-testicular axis and puberty

Puberty is marked by an increase in the pulsatile secretion of GnRH from the hypothalamus. GnRH stimulates the secretion of FSH and LH from the gonadotroph cells of the anterior pituitary gland. In boys, FSH stimulates growth of seminiferous tubules, leading to an increase in testicular volume. FSH also stimulates the Sertoli cells of the testes to produce inhibin B, which inhibits secretion of FSH. LH stimulates the Leydig cells of the testes to produce testosterone, which induces growth of the penis, deepening of the voice, growth of facial and body hair, and increases in muscularity. The high local concentration of testosterone in the testes further stimulates growth of the seminiferous tubules. Some testosterone is converted to estradiol, which stimulates growth and skeletal maturation and frequently leads to some breast development (gynecomastia).