The relationship between serum testosterone (T) and the metabolic syndrome was examined in a systematic review of 20 manuscripts (13 cross sectional, 3 longitudinal and 4 randomized controlled studies). Consistent outcomes of these papers were presented and compared.
Metabolic Syndrome (MetS) is a cluster of risk factors including abdominal obesity, increased blood glucose and/or insulin resistance, dyslipidemia and hypertension. MetS is associated with a two-fold increase of 5-10 year risk of cardiovascular (CV) diseases and five-fold increase in risk for type 2 diabetes (T2DM). The presence of hypogonadism in men with MetS and erectile dysfunction (ED) is associated with a greater severity of symptoms of sexual dysfunction, other than ED. ED and male hypogonadism have been recently recognized as possible predictors of forthcoming metabolic diseases and CV events. ED subjects have been considered paradoxically “lucky” because this symptom might offer them the opportunity to screen for the presence of ED-associated morbidities, including hypogonadism.
The specific mechanism through which hypogonadism might affect CV health have not been completely clarified, but both clinical and animal evidence shows that T exerts a favorable effect upon vascular reactivity, inflammation, cytokine production and adhesion molecule expressions, as well as on serum lipid concentration and hemostatic factors. It has been speculated that the presence of hypogonadism and ED in subjects with MetS should alert clinicians that such people deserve a more intensive lifestyle changes at an early stage to delay progression to a higher risk category. Unfortunately, no study has specifically evaluated this point in subjects with ED, whereas only a few RCTs on the metabolic effect of T replacement therapy in subjects with MetS have been published.
MetS is significantly associated with an overall lower total testosterone (TT). This difference is more evident in studies conducted in subjects with ED than in those without. The association among MetS, hypogonadism and ED is well recognized; in fact the syndrome is highly prevalent in subjects with ED and low T. The specific mechanisms linking MetS and male hypogonadism have not been completely clarified. Low T could be considered one of the many adverse consequences of overweight and obesity. On the other hand, hypogonadism could contribute to the accumulation of excess fat and to the reduction of insulin sensitive muscular mass, thus establishing a vicious cycle. Insulin resistance has been recently considered the common pathogenic link between ED, MetS and male hypogonadism.
Reference: Corona G, Monami M, et al. Testosterone and metabolic syndrome. J Sex Med 2011;8:272-283.