Classic male hypogonadism is associated with known adverse effects including decreased libido, erectile dysfunction, osteoporosis, and changes in body composition. Recently we have come to appreciate that reduction in serum testosterone levels resulting from aging or chronic disease or androgen deprivation therapy have consequences similar to those seen in classic male hypogonadism which include increased fat mass, decreased lean body mass, decreased muscle strength and sexual dysfunction. These data suggest that low testosterone levels may represent a newly recognized cardiometabolic risk factor. Therefore, we carried out a careful review of the literature, focusing on major turning points of research and studies which gave more important and controversial contribution to the cardiovascular role of testosterone. Observational studies and clinical trials investigating the relationship between testosterone levels and cardiovascular disease and mortality were identified by Medline search. The results were synthesized, tabulated, and interpreted. The aim of this review is to discuss the association between low testosterone levels and adverse metabolic profile such as insulin resistance, metabolic syndrome, and diabetes. We’ll also investigate the potential mechanisms by which male hypogonadism, especially age related or induced by androgen deprivation therapy, may increase cardio-metabolic risk. Finally we’ll detail the emerging relationship between low testosterone and mortality in men addressing also the reverse hypothesis that low testosterone has a protective role by turning off testosterone-dependent functions.