Diabetes mellitus can cause the parotid gland to non-inflamedly enlarge and affects blood flow in small vessels.
A study compared 38 people with diabetes to 38 healthy controls using ultrasound to measure the parotid glands' volume, stiffness, and blood supply.
Results showed diabetic patients had larger parotid glands and lower microvascularity, with those on antidiabetic medication having even larger glands; longer diabetes duration correlated with reduced blood supply.