HNF1A and type 2 diabetes mellitus: We observed no statistical differences for fasting insulin (HNF1A‐MODY studies: SMD 0.18 [95% CI −0.21, 0.58] mIU/l, p = .36, n = 6; I2 = 66%, Ph = .01; type 2 diabetes studies: SMD −0.60 [95% CI −1.24, 0.04] mIU/l, p = .07, n = 3; I2 = 77%, Ph = .01).