Effects of two low-dose oral contraceptives on circulating components of the coagulation and fibrinolytic systems.

The authors studied the effects on plasma levels of coagulation and fibrinolysis factors of 2 currently used "sub-50" oral contraceptives (OCs) 1 containing 750 mcg lynestrenol and 37.5 mcg ethinyl estradiol (LYN-EE) and the other containing 150 mcg levonorgestrel and 30 mcg ethinyl estradiol (LNG-EE) in groups of about 25 women ages 21 +or- 2 years. After 3 months plasminogen levels increased in the 2 experimental groups by 40% and 32% respectively. This change was positively correlated with changes in ceruloplasmin levels indicating that an estrogenic effect might be involved. Histidine-rich glycoprotein concentration decreased by 26% and 16% respectively. Tissue-type plasminogen activator (t-PA) activity increased by 260% and 167%; t-PA antigen decreased by 12% and 18% and t-PA inhibitor activity decreased by 31% and 32% respectively. In the coagulation system in both groups factor 12 increased by 47% and 34% respectively. The main inhibitor of factor 12 C1-inactivator decreased slightly but this was significant only in the LNG-EE group. The von Willebrand factor antigen fell by 8% and 9% whereas factor 8 activity did not change. Antithrombin 3 antigen decreased by 14% in both groups. Factor 9 activity increased by 15% and 21%. The difference in hormonal effects of both preparations was reflected by hormonal effects of both preparations was reflected by the increase in sex hormone binding globulin (by 130% and 21%) and ceruloplasmin (by 98% and 51%) indicating that LYN-EE had a more estrogenic potency than LNG-EE. In a control group of 25 matched subjects who were observed simultaneously the authors found no significant changes. It is concluded that both OC preparations produce "procoagulant" as well as profibrinolytic" changes. In general these changes may compensate each other but this is not necessarily the case in individual subjects. (authors)