Hypoparathyroidism in diabetes mellitus.

Serum immunoreactive parathyroid hormone (iPTH) and indices of mineral and glucose metabolism were determined in 58 insulin treated diabetic patients (duration of disease 1-11 years). The mean serum iPTH level in all diabetic patients, measured simultaneously with sera from normal subjects, was 55% of normal mean (P < 0.01). The diabetic patients had hypomagnesaemia (P < 0.001), hypercalciuria (P < 0.001) and a 9.6% decrease in bone mass (P < 0.001). Low serum iPTH values were correlated with high glycosuria (R = -0.28, P < 0.05) and with long duration of diabetes (R = -0.31, P < 0.02). Patients with both high glycosuria and long diabetes duration had especially low iPTH values (mean 16 ng/l, n = 16) compared with patients with both low glycosuria and short diabetes duration (mean 32 ng/l, n = 15, P < 0.005) and with normal subjects (mean 37 ng/l, n = 28, P < 0.001). The 16 patients with low serum iPTH values also had higher urinary calcium excretion rate (P < 0.05) than the 15 patients with low glycosuria and short duration of diabetes. The diabetic hypoparathyroidism may be secondary to a primary disturbance of bone metabolism, with a negative net calcium balance.