BackgroundWhen exogenous testosterone or treatments to elevate testosterone (human chorionic gonadotropin [HCG] or Clomid) are given to men with underlying familial and/or acquired thrombophilia, deep venous thrombosis and pulmonary embolism often occur, and may recur despite adequate anticoagulation if testosterone therapy is continued.Case PresentationIn a 55 year old white male, referred to us because of 4 thrombotic events, 3 despite adequate anticoagulation over a 5 year period, we assessed interactions between thrombophilia, exogenous testosterone therapy, and recurrent thrombosis. In 2009, despite low-normal serum testosterone 334 ng/dl (lower normal limit [LNL] 300 ng/dl.), he was given testosterone (TT) cypionate (50 mg/week) and HCG (500 units/week) for presumed hypogonadism. Ten months later, with supranormal serum T (1385 ng/dl, UNL 827 ng/dl) and estradiol (E2) 45 pg/ml (UNL 41 pg/ml), he had a pulmonary embolus (PE), and was then anticoagulated for 2 years (enoxaparin, then Coumadin). Four years later, on TT-HCG, he had his first deep venous thrombosis (DVT). TT was stopped, HCG continued; he was anticoagulated (enoxaparin, then Coumadin, then apixaban (Eliquis), then fondaparinux (Arixtra)). One year after his first DVT, on HCG, still on Arixtra, he had a second DVT (5/2015), was anticoagulated (enoxaparin+Coumadin), with a Greenfield filter placed, but 8 days later had a second PE. The Lupus anticoagulant was found to be present. After stopping HCG, and maintained on Coumadin, he has been free of further DVT-PE for 6 months.ConclusionWhen DVT- PE occur on TT or HCG, in the presence of thrombophilia, TT- HCG should be stopped, lest DVT-PE reoccur despite concurrent anticoagulation.