Testosterone Increases Human Platelet Thromboxane A 2 Receptor Density and Aggregation Responses

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Abstract
Background The incidence of thrombotic cardiovascular disease is greater in men than in premenopausal women. Testosterone has been implicated as a significant risk factor for cardiovascular disease and for acute myocardial infarctions and strokes in young male athletes who abuse anabolic steroids. Thromboxane A2 (TXA2) is a vasoconstrictor and platelet proaggregatory agent that has been implicated in the pathogenesis of cardiovascular disease. We therefore tested the hypothesis that testosterone regulates the expression of human platelet TXA2 receptors. Methods and Results In a double-blind, placebo-controlled, randomized, parallel-group study, we determined the effects of testosterone cypionate 200 mg IM given twice, 2 weeks apart, or saline placebo in 16 healthy men. Platelet TXA2 receptor density (Bmax) and dissociation constant (Kd) were measured by use of the TXA2 mimetic 125I-BOP. Platelet aggregation responses to I-BOP and to thrombin and plasma testosterone concentrations were measured before trea...