Effects of a low-oestrogen oral contraceptive on urinary excretion of luteinizing hormone and ovarian steroids.

The urinary gonadotrophin and ovarian steroid excretion pattern was studied in five women taking an oral contraceptive formulation consisting of mestranol 50 mug and norethisterone 1 mg. Both the pretreatment and post-treatment cycles were normal. The ovulatory peak of luteinizing hormone (LH) during the treatment cycles was uniformly suppressed, but LH continued to be excreted within the normal range. In one fifth of the treatment cycles there was a pronounced and sustained rise of oestrogen output in the absence of ovulation, and in many of the other treatment cycles oestrogen levels suggested that active ovarian steroidogenesis was taking place.