Ovarian function during treatment with lynoestrenol 0.5 mg daily.

Twenty-four women, all with normal ovulatory menstrual periods, were studied during in total 64 cycles on lynoestrenol 0.5 mg daily and during 11 control cycles. The 24-hour urines were collected for assay of total oestrogens on the 21st, 22nd and 23rd days of viz. the 1st, 4th, 6th and 12th cycles and for pregnanediol on the 22nd and 23rd days of the same cycles. Oestrogen excretion was at the same level during treatment and control cycles. All the control cycles and 9 and 14 % respectively of the treatment cycles were ovulatory judging by the plasma progesterone and the pregnanediol excretion. On the basis of the latter parameter there was a certain luteal activity during 36 % of the treatment cycles. In all cycles but one, however, the plasma progesterone and the pregnanediol excretion were lower than during the control cycles. It must be assumed, therefore, that lynoestrenol in a dose of 0.5 mg daily inhibits the ovulation or function of the corpora lutea in practically all cases.