Simultaneous Radioimmunoassay of Plasma FSH, LH, Progesterone, 17-Hydroxyprogesterone, and Estradiol-17β During the Menstrual Cycle

Plasma levels of FSH, LH, progesterone (P), 17-hydroxy-progesterone (17-OHP), and estradiol-17β (E2) were measured daily by radioimmunoassay in eleven menstrual cycles from eleven normally menstruating women. The following criteria were used as indirect evidence for a normal ovulatory cycle: 1) mid-cycle LH peak, 2) luteal phase of 12–16 days duration, and 3) plasma progesterone above 5 ng/ml 5–8 days after the LH peak. Nine of eleven cycles studied were considered normal. A mid-cycle peak of E2 and 17-OHP was observed in every normal cycle studied. In one of the normal cycles, two peaks of plasma E2 occurred respectively on days 9 and 22. However, 17-OHP levels were low on day 9 and elevated on day 22. A gonadotropin surge occurred on day 22 followed by a normal luteal phase. The other two abnormal cycles studied either showed low levels of E2 and 17-OHP or a peak of only one of the two steroids. The data suggest that in women, there is a relationship between the steroids 17-OHP and E2, and the mid-cycle surge of gona-dotropins.