Suppression of the midcycle LH surge by a low-dose mestranol-lynestrenol oral combination

Abstract

In a group of nine ovulating women receiving a low-dose mestranol-lynestrenol combination, the daily fluctuations of plasma LH concentration were measured by radioimmunoassay. In each woman a pre-treatment control cycle was investigated basing the occurrence of ovulation on the biphasic nature of the basal body temperature, the typical midcycle LH surge and the urinary pregnanediol excretion. The daily administration of 0.040 mg mestranol — 1.0 mg lynestrenol produced in all volunteers a complete suppression of the midcycle LH surge. In half of the cases the basal LH pattern showed unstable and slightly elevated levels. Administration of 0.040 mg mestranol alone produced a strong stimulating effect on LH secretion. On the other hand, administration of 1.0 mg lynestrenol alone produced the suppression of the LH discharge without changing the basal values.