Topic overview

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The HPG axis provides the framework for understanding reproductive hormones: GnRH signals the pituitary to release LH and FSH, which act on different gonadal cells. FSH supports spermatogenesis through Sertoli cells in males and estrogen production through granulosa cells in females. LH stimulates testosterone production by Leydig cells and, in females, promotes androgen production in theca cells; the mid-cycle LH surge triggers ovulation. The lesson also surveys sex-steroid synthesis from cholesterol and the actions of testosterone, estrogens, and progesterone. It connects these hormones to reproductive processes and other functions, including endometrial changes, bone health, and secondary sex characteristics, while highlighting feedback regulation such as inhibin B’s suppression of FSH.