Effect of orally administered oestrogens on gonadotrophin levels in post-menopausal women.

The gonadotrophin-suppressing effect of 4 peroral oestrogen regimens (A: 2.5 mg piperazine oestrone sulphate; B: 1.25 mg piperazine oestrone sulphate + 5.0 mg oestriol; C: 2.0 mg oestradiol valerate; D: 10.0 mg oestriol; all administered daily) was studied in 7 post-menopausal women, in the absence, and then in the presence of daily oral doses of 250 micrograms of levonorgestrel. A randomized, complete cross-over design was used, and from each volunteer 80 blood samples were drawn during a period of 252 days for the assay of immunoreactive follicle stimulating hormone (FSH), luteinizing hormone (LH) and bioactive LH levels. All 4 formulations significantly diminished pretreatment gonadotrophin levels. Combination with levonorgestrel enhanced the suppressive effects. Subsequent placebo administration for a week restored gonadotrophin levels to those found previously during oestrogen administration, but not to pretreatment levels. Regimen D exhibited the relatively weakest and regimens A and B the strongest suppression, both in the absence and in the presence of levonorgestrel. Treatment with all oestrogen formulations decreased, and the addition of levonorgestrel increased the ratio of bioactive (B) to immunoreactive (I) LH. Seven days of placebo administration abolished the effect of levonorgestrel, but not that of the various oestrogens on the B/I ratios.