Testosterone treatment or testosterone therapy is used to treat people with abnormally low levels of testosterone. Recent studies have indicated that testosterone treatment may increase the risk of venous thromboembolism (VTE), a condition characterized by the formation of blood clots in the deep veins of the body. This study aims to determine the risk of VTE associated with the use of testosterone treatment in men.

This population-based cohort study included a total of 19,215 patients with confirmed VTE, along with 909,530 age-matched controls. The following mutually exclusive testosterone groups were identified: current treatment, recent (not current) treatment, and no treatment. The primary outcome of the study was rate ratios of VTE in association with testosterone therapy.

The rate ratio (adjusted) of VTE was 1.25 for current treatment vs. no treatment. During the first six months of testosterone treatment, the RR of VTE was 1.63. After six months of treatment, the RR of testosterone treatment was 1.00, which further decreased to 0.68 after treatment cessation. The rate ratio was higher in patients without pathological hypogonadism (1.86) and without a known risk for VTE (1.91). 

The research concluded that initiating testosterone treatment was associated with an increased risk of VTE, which declined after six months.

Ref: https://www.bmj.com/content/355/bmj.i5968