Serum gonadotropin and ovarian steroid levels in women during administration of a norethindrone-ethinylestradiol triphasic oral contraceptive.

We studied the inhibitory effect of a triphasic oral contraceptive (OC) regimen on the pituitary and ovarian function in 29 normal, healthy women. ORTHO* 7/7/7 Tablets contain a constant low dose of ethinylestradiol (EE) and a step-wise increasing level of norethindrone (NE). The pills for the first, middle and last weeks of the 21-day regimen contained, respectively, 0.5, 0.75, and 1.00 mg NE, and all contained 0.035 mg EE. The subjects were divided into 3 groups on the basis of their histories of OC use. Ten had not taken an OC in the previous 2 months, 10 were switched to this study from a fixed-dosage combination OC containing 0.050 mg estrogen, and 9 had been taking ORTHO 7/7/7 Tablets for 5 or more cycles. Serum levels of FSH, LH, estradiol and progesterone were measured and statistically compared with those from 5 normal, untreated women. The results from all study cycles showed that the four hormone profiles were significantly suppressed as compared to the normal patterns. Thus, one mode of action of this new triphasic OC is to inhibit ovulation by suppression of pituitary-ovarian function. This OC treatment appeared to be equally effective among women with varying prior histories of OC therapy.