Parathyroid hormone secretion in diabetes mellitus.

To investigate the parathyroid function in diabetes mellitus, we performed an oral phosphate load in 6 diabetic patients and 6 nondiabetic subjects without renal failure (serum creatinine less than 1.5 mg/dl). Each subject received a total of 2.0 g of phosphate daily per os on 5 consecutive days. Blood and urine samples were obtained daily before and 2 h after the administration of phosphate in the morning. All subjects responded with a similar increase in the serum phosphorus concentration and fall in the ionized calcium concentration. Intact parathyroid hormone levels rose by 2.6-fold in the control subjects but by less than 1.5-fold in the diabetic subjects. It was concluded that hyporesponsiveness of the parathyroid hormone to phosphate administration was found in the diabetic patients without renal failure.