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 < 0.05; I²: 79%). It is also evident that SHBG in low TT studies behaves as a risk factor for T2DM in the same way as FT, although without statistical significance. bT behaves as a protective factor. There is no association between estrogen, DHT and T2DM.

In adult men with low TT values, there is a greater risk of developing a newly diagnosed of T2DM. SHBG values in low TT patients also present a higher risk of T2DM as the same FT but without statistical significance. bT behaves as a protective factor We have not found an association between risk of T2DM and the levels of estrogen, DHT although there are very few studies that report these hormones.