Testosterone levels and risk of newly diagnosed type 2 diabetes mellitus in adult men: systematic review and meta-analysis

Testosterone is a metabolically active hormone in males for metabolic homeostasis. Although the coexistence of low testosterone levels and type 2 diabetes mellitus (T2DM) have been associated, there are no reports that evaluate alterations in total testosterone (TT) levels and the risk of newly diagnosed T2DM. This review evaluates this question in adult men with high or low levels of total testosterone (TT), as well as the role played by other hormones such as free testosterone (FT), sex hormone binding globulin (SHBG), dihydrotestosterone (DHT), estrogens and testosterone bioavailable (bT). We searched for studies published up to July 30, 2023, in five databases, following a PECO strategy. We found twenty-two studies for quantitative analysis and meta-analyzed the same quantity of studies. This first meta-analysis incorporates the assessment of the risk of low TT and T2DM in longitudinal studies. 43,038 adult men are included. Our meta-analysis shows that there is an association between low TT levels and the risk of newly diagnosed T2DM (OR 1.52; 95% CI 1.10-2.10; p