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A combination of 1.0 mg dl-norgestrel and 0.1 mg ethinylestradiol (EE) was administered orally at 36 hours after the detection of the luteinizing hormone peak and again at 48 hours in 12 healthy volunteers with normal menstrual cycles. The effects on ovarian function were studied by comparing the daily serum levels of progesterone (P), 17 alpha-hydroxyprogesterone, and estradiol (E2) in control (placebo) and treatment cycles. Five subjects showed no significant change in the levels of these steroids but had a shortened luteal phase. The treatment significantly decreased both P and E2 levels in three subjects, while two subjects showed diminished E2 levels only. The remaining two subjects had lower P levels and fluctuating E2 patterns. Endometrial biopsies from both study cycles indicated asynchronous development of the epithelial and stromal components in the treatment cycle. These findings (abnormal luteal phase steroid levels and duration and outphased endometrial development) indicate that corpus luteum function was variously affected by the action of norgestrel-EE treatment.

A combination of 1.0 mg dl-norgestrel and 0.1 mg ethinylestradiol was administered orally at 18 hours after the detection of luteinizing hormone rise and again at 30 hours in five healthy volunteers with normal menstrual cycles. The effects on ovarian function were studied by comparing the daily serum levels of progesterone (P), 17 alpha-hydroxyprogesterone, and estradiol (E2) measured in a control (placebo) cycle with those in two consecutive treatment cycles. Treatment did not alter the steroid levels in one subject. P was suppressed in one or both treatment cycles of four subjects. E2 was suppressed in both treatment cycles of one subject and produced widely fluctuating patterns in another. The hormonal patterns in the two consecutive treatment cycles of the same individual were similar in all but one instance, where only the P level in the second treatment cycle was diminished. These results showed that this treatment can elicit steroidogenic responses of varying degrees and duration. The contraceptive action may lie in the altered P and/or E2 level at certain points in the menstrual cycle.