Cheng TS, et al. - A systematic review and meta-analysis was conducted to investigate a correlation between puberty timing and T2D or impaired glucose tolerance (IGT), with and without adjustment for adiposity, and to evaluate the potential contribution of puberty timing to the burden of T2D in the United Kingdom. PubMed, Medline, and Embase databases were searched for publications until February 2019 on the timing of any secondary sexual characteristic in boys or girls in relation to T2D/IGT. They applied inverse-variance-weighted random-effects meta-analysis to pool reported estimates, and using meta-regression to explore sources of heterogeneity. They included 28 observational studies to examine all age at menarche (AAM) in women (combined N = 1,228,306); only 1 study additionally included men. Consistent association was found between earlier AAM and higher T2D/IGT risk, independent of adiposity. They found that a substantial proportion of T2D in women is related to early menarche, which would be predicted to elevate in light of global secular trends towards earlier puberty timing. The data demonstrates the need to distinguish the underlying mechanisms linking early menarche to T2D/IGT risk.