Supporting a genetically and environmentally reactive role for autoimmunity, Warncke et al found that, in 1050 infants and children (aged 4 months to 3.6 years) with a high genetic risk of type 1 diabetes, glycaemic trajectories were determined by sex, BMI, glucose-related genetic risk score and the type 1 diabetes-susceptible INS genotype. Here, INS is linked to type 1 diabetes mellitus.