This module covers the physiology of human reproduction and the role of the hypothalamic-pituitary-gonadal axes in fertility. It explores the HPO axis in females and HPT axis in males, including the roles of GnRH, FSH, LH, estrogen, progesterone, and testosterone. The module explains menstrual cycle regulation, ovulation, spermatogenesis, and hormonal feedback mechanisms. It also examines how nutrition, stress, metabolic status, and lifestyle factors can influence reproductive function and fertility.