EFFECTS OF CONTINUOUS DAILY ADMINISTRATION OF 0.5 MG OF NORETHINDRONE ON THE PLASMA LEVELS OF PROGESTERONE AND ON THE URINARY EXCRETION OF LUTEINIZING HORMONE, PREGNANEDIOL AND TOTAL OESTROGENS

Abstract

Daily determinations of the plasma level of progesterone and the urinary excretion of LH, total oestrogens and pregnanediol were performed in 4 subjects during one control cycle, immediately followed for 2 or 3 months of daily treatment with 0.5 mg of norethindrone continuously. The control cycles were ovulatory according to all the parameters investigated. During treatment the mid-cycle LH peak disappeared in all cases while the basal LH excretion showed considerable day to day variations. The excretion of total oestrogens was increased in all subjects but did not show the normal biphasic pattern. Periods of increased oestrogen excretion also appeared in the subjects with consistently low progesterone and pregnanediol levels during the treatment. In two cases, all signs of luteal activity immediately disappeared after the commencement of treatment. The other cases had one and three periods of increased progesterone and pregnanediol levels respectively. However, these periods were shorter than those of the control cycles. One of the subjects had regular menstrual bleeding while the other three had more or less irregular vaginal flows, often appearing during elevated but declining oestrogen excretion.