Is a Previously or Currently Reduced Testosterone Level in Male Patients with Type 2 Diabetes Mellitus a Risk Factor for the Development of Coronary Artery Disease? A Systematic Review and Meta-analysis

INTRODUCTION: We aimed to systematically investigate the association between testosterone level and cardiovascular risk in male patients with type 2 diabetes mellitus (T2DM) by comparing male T2DM patients with low testosterone levels to male T2DM patients with normal testosterone levels at baseline in terms of the number of cases of coronary artery disease (CAD). METHODS: Online databases were carefully searched for studies relating to testosterone, diabetes mellitus, and cardiovascular risk by using the search terms ‘testosterone,’ ‘diabetes mellitus,’ and ‘coronary artery/cardiovascular disease.’ The only endpoint in this analysis was CAD/atherosclerosis/coronary plaque/major adverse coronary event prior to or following testosterone reduction at baseline. The analytical parameters used in this analysis were the risk ratio (RR) with the 95% confidence interval (CI), as obtained using the RevMan 5.3 software. RESULTS: 3467 male patients with T2DM (1079 patients with a low testosterone level versus 2388 patients with a normal testosterone level) were included. The results of this analysis showed that when a random effects model was used, a higher risk of CAD/cardiovascular disease was observed in diabetic patients with a low testosterone level than in those with a normal testosterone level (RR 1.24, 95% CI 0.94–1.63; P = 0.13). However, the difference in risk was not statistically significant. Similarly, with a fixed effects model, a low testosterone level was associated with a higher CAD/cardiovascular risk of disease (RR 1.12, 95% CI 0.98–1.34; P = 0.08); in this case, the difference in risk between the T2DM patients with low and normal testosterone levels approached statistical significance. CONCLUSION: A previously or currently reduced testosterone level was not found to be statistically significantly associated with a high risk of CAD/cardiovascular disease in male patients with T2DM. However, the difference in risk between the T2DM patients with low and normal testosterone levels was observed to approach statistical significance.