Effects of a very low-estrogen oral contraceptive on clotting factors, carbohydrate metabolism and plasma lipids and lipoproteins.

Biological effects, coagulation factors, lipids, lipoproteins, apoproteins and glucose tolerance, of a low dose oral contraceptive (Loestrin, Minestril-20, Parke-Davis, Ann Arbor MI) were monitored in 30 women for 2 or 3 cycles. The pill contains 20 mcg ethinyl estradiol and 1 mg norethisterone acetate. Plasminogen and Factors VII-I rose significantly after 1, 2, and 3 cycles, while fibrinogen and Factor IX were significantly increased only after 2 cycles, and that of Factor II only after 1 cycle. Antithrombin III was significantly lower after 1 and 3 cycles (all p0.01). No significant differences were registered in lipid fractions, triglycerides, total cholesterol, HDL-cholesterol, Apo A1, Apo B, Apo A1/B or HDL/TC. No differences were observed in the 2-hour glucose tolerance or insulinemia. Previous experience has shown that 3 cycles enough time for biological effects to appear, thus this pill formulation has minimal effects.