The GLP-1R expression in pancreas (assumed to be correlated to the beta cell mass) is investigated by 68Ga-NODAGA-exendin-4 PET/CT in T1D subjects with unstable and stable glycaemic control (NCT03785275) as well as during the honeymoon phase in T1D (NCT03917238) and in subject with gestational diabetes (NCT03182296). This evidence concerns the gene GLP1R and type 1 diabetes mellitus.