Analysis of two major Mendelian randomization studies revealed that endogenous testosterone production in men is positively correlated with blood clots, heart attack, and heart failure. Data from at least 200,000 participants were included in the analysis. A proposed mechanism for such a risk is the testosterone conversion into estrogen, in turn contributing to thromboembolism. Testosterone can also increase platelet aggregation via the thromboxane A2 pathway.
Data from these “natural experiments” overall follow the observed increased risk of deep venous thrombosis and heart disease in men who are over-supplemented with exogenous testosterone. On the contrary, low Testosterone levels are also associated with visceral adiposity, low muscle mass, and insulin resistance. From a cardiovascular perspective, future clinical research is needed to identify the balancing point of how much or little testosterone men should have.