The initiation of testosterone treatment was associated with an increased risk of venous thromboembolism, according to a recent study published in the BMJ.

Carlos Martinez, MD, from the Institute for Epidemiology, Statistics, and Informatics in Frankfurt, Germany, and colleagues conducted a population based case-control study to determine the risk of venous thromboembolism associated with testosterone use in men. The study included 370 general practices in the United Kingdom with linked hospital discharge diagnoses and information on all-cause mortality.

The researchers identified 19,215 patients with confirmed venous thromboembolism and 909,530 age-matched controls from a source population that included more than 2.22 million men between January 2001 and May 2013.

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They identified 3 testosterone exposure groups, including participants undergoing current testosterone treatment, participants who received recent but not current testosterone treatment, and participants who did not receive treatment within the previous 2 years. The investigators calculated rate ratios of venous thromboembolism in association with current testosterone treatment compared with no treatment.

The adjusted rate ratio of venous thromboembolism for current testosterone treatment compared with no testosterone treatment was 1.25. The rate ratio of thromboembolism during the first 6 months of treatment was 163, which corresponds to 10.0 additional venous thromboembolisms above the base rate of 15.8 per 10,000 person years.

The rate ratio was 1.00 after more than 6 months of treatment, and it was 0.68 after treatment cessation. The researchers observed a rate ratio of 1.52 among patients with pathological hypogonadism and a rate ratio of 1.88 for patients without it. In addition, the rate ratio for patients with a known risk factor for venous thromboembolism was 1.41, and the rate ratio for those without a risk factor was 1.91.

“The initial increased risk of venous clotting might provoke a secondary response with more fibrinolysis, which tends to dissolve clots and eventually neutralizes the risk,” the study authors noted. “The risk of venous thromboembolism adjusted for underlying risk factors in association with testosterone use was increased early after the start of treatment for men without pathological hypogonadism, a group in which unproven empirical testosterone treatment has been increasingly used over the first decade of this century.”


  1. Martinez C, Suissa S, Rietbrock S, et al. Testosterone treatment and risk of venous thromboembolism: population based case-control study. BMJ. 2016. doi: 10.1136/bmj.i5968.