Daily Variations in Plasma Follicle Stimulating Hormone, Luteinizing Hormone and Progesterone in the Normal Menstrual Cycle1

Abstract

Plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels were measured daily throughout a single cycle in 21 young women with apparently regular menses. Plasma progesterone levels were determined in aliquots of the same samples in 18 of the women. Plasma FSH levels increased in the early follicular phase, dropped to a preovulatory nadir and then rose to a peak usually coincident with or one day after the midcycle LH peak. The FSH peak averaged 19.6 mlU/ml and the LH peak 76.3 mlU/ml. Luteal phase levels of FSH and LH were lower than the follicular phase levels. Luteal FSH levels declined progressively to a nadir which usually occurred 3 or 4 days prior to the onset of the next menses. A late luteal FSH rise occurred after the luteal nadir. In contrast, luteal LH levels remained stable. In each of 4 women, the luteal rise in progesterone occurred after the midcycle gonadotropin peaks. The interval, however, was variable, ranging from 0 to 4 days.