Oral Contraceptive pulmonary artery thrombosis and anti-ethinyl-oestradiol monoclonal IgG.

A 35-year-old woman who had taken an oral contraceptive (50 mcg ethinyl estradiol (EE) plus 500 mcg norethisterone) for 2 1/2 years was hospitalized for a massive left pulmonary thrombosis. A monoclonal IgGgamma gammopathy of about 700 mg/100 ml was found from electrophoretic patterns. After purifying the IgG including separation from bound circulating hormones its binding activity for several steroids was determined by equilibrium dialysis which revealed several steroids as inhibitors of EE binding by IgG with potencies in the following order (decreasing): EE itself 17beta-estradiol progesterone estriol and testosterone. It appears likely that the binding sites of this KgGgamma were the antibody sites and that it may be classified as a monoclonal anti-ethinyl-estradiol antibody. The occurrence of thrombosis and a rare gammopathy in a young woman is unlikely and lends support to the hypothesis that an immunological mechanism is responsible for the thrombotic risk associated with oral contraceptives.