Subgroup analyses revealed significant mean FPG reduction in GCK-MODY (0.50 ± 0.72 mmol/l, p = 0.007), but not in HNF1A-MODY (0.14 ± 0.90 mmol/l, p = 0.56) and T2DM (0.23 ± 1.20 mmol/l, p = 0.52). Here, GCK is linked to type 2 diabetes mellitus.