Yao Q, et al. - This systematic review was conducted to investigate the association of testosterone level with diabetes risk in men. In this meta-analysis, the clinicians revealed that in men, higher testosterone level could significantly decrease the risk of type 2 diabetes. Thus, the findings suggested a reverse-causality scenario in the relation between testosterone deficiency and risk of type 2 diabetes in the study group.

Methods

• The clinicians searched Pubmed, Embase, and Web of Science for an eligible cohort or nested case-control studies published up to August 15, 2017.
• They used meta-analysis to calculate the pooled relative risk (RR) of type 2 diabetes associated with higher testosterone level.

Results

• The clinicians included 13 cohort or nested case-control studies with 16,709 participants.
• Higher total testosterone level could significantly decrease the risk of type 2 diabetes in men (RR = 0.65; 95%CI 0.50-0.84; P=0.001).
• In addition, higher free testosterone level could decrease the risk of type 2 diabetes in men (RR = 0.94; 95%CI 0.90-0.99; P=0.014).
• Both higher total testosterone and free testosterone levels could reduce the risk of type 2 diabetes in men, after excluding 2 studies which did not calculate RRs by quartiles of testosterone levels, and the pooled RRs were 0.62 (95%CI 0.51-0.76; P < 0.001) and 0.77 (95%CI 0.61-0.98; P=0.03), respectively.