Effect of treatment with testosterone on endothelial function in hypogonadal men: a systematic review and meta-analysis

Despite several studies showing an inverse correlation of total testosterone with endothelial damage, the effect of testosterone replacement therapy (TTh) on endothelial function has been scarcely investigated. In order to systematically assess the relationship between endothelial dysfunction and TTh, we performed a review and meta-analysis of available prospective and cross-sectional studies. A thorough research was performed on MEDLINE for hypogonadism and endothelial dysfunction. We retrieved 28 papers, among which 23 were excluded for different reasons: five papers accounting for six studies (two crossover randomized clinical trial (RCT), three observational, one placebo controlled RCT) were therefore included in analysis. Overall, 86 patients with hypogonadism were included in analysis (mean age 49.57 ± 8.85 years). Baseline total testosterone serum levels were 8.11 ± 2.42 nmol/L and significantly increased while undergoing TTh (standard mean difference (SMD) 2.93 nmol/L, 95% confidence interval (CI) 1.89:3.97, p < 0.001). Due to the paucity of studies available, flow-mediated dilation (FMD) was chosen as the best surrogate marker of endothelial dysfunction. FMD did not significantly change after testosterone administration (SMD -0.22, 95% CI -1.29:0.84, I2 = 90%); acute testosterone administration was associated with an increase in FMD, whereas a reduction in FMD emerged following chronic treatment, but statistical significance was not reached for both effects. This is the first meta-analysis study assessing the influence of TTh on endothelial function; however, results are far from conclusive, as proven by the high heterogeneity.