Duration, Amplitude, and Specificity of the Midcycle Gonadotropin Surge in Nonhuman Primates

The midcycle luteinizing hormone (LH) surge signals key changes within the mature, preovulatory follicle, including resumption of oocyte meiosis, lutein-ization of the follicle wall, ovulation, and early development of the corpus luteum (1). The duration of the LH surge during normal ovarian cycles is considerably longer (48 hours) in women (2) and rhesus monkeys (3) compared with many nonprimate species (rats and rabbits, 4–6 hours; sheep and cattle, 10–16 hours). The concept that surge requirements vary for periovulatory events has emerged from studies in nonprimate species with resumption of oocyte meiosis requiring less LH exposure than that for optimal luteal development (4–6).