Synthesis and release of gonadotropins: effect of an oral contraceptive

A double-stimulation test with 100 micrograms gonadotropin-releasing hormone per dose given twice within two hours was carried out in eight normally cyclic women before and during treatment with a combined oral contraceptive (30 micrograms ethinyl-estradiol + 150 micrograms desogestrel). The test was performed on days 8 to 11, 19 to 22, and 24 to 27 of a control cycle, and during the first and third treatment cycles. This oral contraceptive was found to diminish the capacity of the gonadotropes for the synthesis of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to a higher degree than that for the acute release in each treatment cycle. During the treatment-free interval, the reaction of LH differed from that of FSH: while the release of the former remained suppressed, that of FSH did not differ from the control cycle.