ABSTRACT
Serum levels of LH, FSH and prolactin and plasma levels of estradiol and progesterone were measured by radioimmunoassay from 8 healthy volunteers on no medication for at least 3 months prior to study and with histories of regular menstrual cycle. The following criteria were used to define a normal menstrual cycle:1) mid-cycle LH surge, 2) luteal phase duration between 12 and 16 days, 3) plasma progesterone levels above 5 ng/m1 5-10 days after LH surge. Six of eight cycles studied were considered normal. Serum levels of LH from 6 women were fair1y constant through the cycle, except at midcycle, when a surge occurred. The rapid increase of LH secretion was during the late follicular phase with a mean peak value of 147.5 mIU/ml. Concentration of FSH started to rise after the onset of menses and decreased slight1y during the late follicular phase. FSH rose sharply at midcycle with a mean peak value reaching 36.8 mIU/ml. Following the midcycle FSH and LH surge, FSH and LH decreased sharply and remained at lower concentration during the luteal phase than during the follicular phase. Serum prolactin concentrations fluctuated throughout the menstrual cycle. There was no peak value of prolactin concomitant to the LH peak. Plasma estradiol gradually increased during the follicular phase reaching a maximum of 354.3 pg/ml prior the midcycle LH surge. Following its peak, the level of estradiol dropped sharply and started to increase from the 3rd day after LH peak, rising to 235.9 pg/ml during the midluteal peak. Plasma progesterone levels remained consistently low during the follicular phase and started to rise after the midcycle surge of LH. This rise persisted from day 5 to day 9 after the LH surge, showing a mean value of 26.1 ng/m1. Afterward, a sharp decline occurred resulting in menstruation. Two cycles studied were considered abnormal. Both cycles showed a "short luteal phase".