Levels of Protein S during the Normal Menstrual Cycle and in Women on Oral Contraceptives Low in Estrogen

Abstract

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.

A Randomized Cross-over Study on the Effects of Levonorgestrel- and Desogestrel-containing Oral Contraceptives on the Anticoagulant Pathways

“…In contrast, treatment with levonorgestrel-containing OC resulted in a slight, but not significant increase of the protein S level. This finding differs from an early report in which lower protein S levels were found to be associated with the use of a levonorgestrel-containing OC (35), but it is in agreement with a later study in which 11 women were followed during the first cycle of levonorgestrel-containing OC use (36) and in which a decrease in total protein S was observed during the second week of hormone administration but no significant change was observed at the end of the pill cycle. Thus, the increased protein C levels observed with both OC preparations will be counteracted by decreased protein S levels during the use of desogestrel-containing OC but not during the use of levonorgestrel-containing OC.…”