Similar to the previous reports, TRT resulted in a significant increase in hemoglobin levels.36 However, none of the individual prostate-related adverse events significantly differed between groups, including incident prostate cancer, which showed no difference between the TRT group and placebo.34 In 2016, Boyle et al. reported results of a meta-analysis on prostate cancer in TRT trials. The TRT group had a significantly greater incidence of all prostate-related adverse events, with a pooled odds ratio of 1.78 (95% CI, 1.07–2.95). All four studies included in this meta-analysis evaluated the effects of TRT on LVEF as well. The authors also verified that the odds ratio for having hypogonadism was significantly higher in obese men, and there was a statistically significant negative correlation between total T level and BMI.15 Testosterone replacement therapy (TRT) has been shown to decrease fat mass. Whether low T and increased mortality are simply covariates or a causal relationship remains to be proven. This type of study design generally entails measurement of a single, or possibly two, serum T levels in participants, whose health trajectories are then followed over the ensuing years. Similar to these cross-sectional analyses, longitudinal data have shown mixed findings, although most studies have not demonstrated a relationship between circulating T levels and incident CVD. However, while these types of analyses attempt to control for covariates, they do not allow clear discernment as to whether T levels are directly related to CVD risk or, alternatively, serve as a marker of ill health overall. The authors also found higher vascular and all-cause mortality among men with low plasma T levels when compared with men without androgen deficiency. More recently, Malkin et al. reported a 24% prevalence of biochemical T deficiency (using either total or bioavailable T concentrations) among men with coronary disease. Furthermore, the actual exposure to T among the subjects is not clear, as the treatment group was categorized on the basis of a single-filled prescription, and post-treatment T levels were not measured nor was long-term use confirmed. All patients included in this retrospective analysis had low serum T concentrations and had undergone coronary angiography. Vigen et al. reported an association between TRT and the incidence of myocardial infarction, stroke or death in approximately 8000 male veterans . In contrast to the cross-sectional studies mentioned above, these studies have attempted to analyze large populations of men who received exogenous T, presumably as TRT. Nonetheless, the results of the TOM trial provide important cautionary information regarding the potential for TRT to be harmful in at least some populations of older men and points to the need for larger studies. Further, subjects in the TOM trial had higher baseline BMI, higher triglycerides, and lower HDL than individuals included in the second study. The same study demonstrated a prevalence of hypogonadism of 24% in men with coronary artery disease, by strict criteria, which is approximately three times higher than the expected background rate. Bioavailable testosterone assays have been utilized in several studies of men with coronary artery disease and more consistently demonstrate decline with age. Multiple cross-sectional studies have demonstrated a fall in androgen levels with advancing age.16, 17, 18, 19, 20, 21, 22, 23, 24, 25 However, unlike women, men do not experience the well characterized, sudden and rapid decline in sex hormone levels and cessation of reproductive capability as they age. Secreted testosterone circulates in the blood in its free form or bound to carrier proteins. In addition to summarizing clinical and preclinical data, this review provides insight on potential mechanisms of action of testosterone on CVD, applications of this knowledge to clinical settings, and avenues for future research. At least nine out of the 10 ‘Wilson and Junger criteria' for screening99 are satisfied by screening for hypogonadism in men with CAD.