Age effects of follicle-stimulating hormone and pulsatile luteinizing hormone secretion across the menstrual cycle of premenopausal women.

To characterize the differential aging response in gonadotropin secretion that occurs before menopause, we assessed pulsatile LH and serial FSH, estradiol (E2), and progesterone (P) concentrations in aging women across the menstrual cycle. We conducted 96 daytime studies during the follicular, midluteal, and late luteal phases of the same menstrual cycle in 32 volunteers, aged 40-50 yr (n = 16) and 19-39 yr (n = 16). Mean cycle length was shorter in the older women (26 +/- 0.4 vs. 27.6 +/- 0.6 days; P = 0.02), but mean plasma E2 and P values were similar in the two age groups. Mean plasma FSH was higher in the older group on all 3 study days. For LH, an age difference was observed during the late luteal phase, when mean plasma LH and pulse amplitude were higher in women over 40 yr of age (mean LH, 6.4 +/- 0.7 vs. 3.0 +/- 0.5 IU/L (P = 0.002); mean amplitude, 4.0 +/- 0.5 vs. 2.8 +/- 0.2 IU/L (P = 0.03)]. Pulse frequency was higher in the older group, but not different from that in younger women on all stud...