Levels of protein s during the normal menstrual cycle and in women on oral contraceptives low in estrogen

Total protein S, a coagulation regulating protein, was determined by an electroimmunoassay in samples of plasma collected during one menstrual or hormone-induced cycle in 15 young women and 11 women using oral contraceptives with 30 μg ethinyl estradiol and 150 μg levonorgestrel. Distinct individual levels caused the with-in-group variations of plasma total protein S to be larger than the individual variations. There was no statistically significant difference between the groups, but in the hormone group there was a slight but statistically significant decrease during the hormone-induced cycle.