Aims/Introduction A decrease in the size of the pancreas is observed in islet autoantibody‐positive non‐diabetic donors and acute‐onset type 1 diabetes irrespective of the diabetes duration. Little is known, however, about the relationship between the size of the pancreas and type 1 diabetes subtypes, including fulminant type 1 diabetes. Materials and Methods We examined the pancreatic volume (PV) in 44 adult patients with type 1 diabetes (16 acute‐onset type 1 diabetes, 18 slowly progressive type 1 diabetes and 10 fulminant type 1 diabetes) and 39 age‐ and body mass index‐matched non‐diabetic controls. PV was measured by computed tomography. The ability to secrete insulin was assessed by stimulated C‐peptide after intravenous glucagon administration. Results PV was significantly correlated with bodyweight in both control participants and type 1 diabetes patients. The PV index (PVI; PV/bodyweight) was decreased by 39% in type 1 diabetes compared with that in controls. PVI was significantly decreased in acute‐onset type 1 diabetes patients and slowly progressive type 1 diabetes patients (both P
