PARATHYROID FUNCTION IN SPONTANEOUS PRIMARY HYPOTHYROIDISM

Abstract

SUMMARY Calcium and phosphorus metabolism were studied in 22 patients with spontaneous primary hypothyroidism. Two patients were found to have hypercalcaemia but the mean serum calcium concentration of the group was significantly less than that of control subjects. The renal tubular reabsorption of phosphate was decreased and could be increased to normal with small calcium infusions. The response to calcium deprivation and to infusions of EDTA was abnormal and suggested an impaired ability to mobilize calcium from bone. There was a significant correlation between the defect in calcium mobilization, as judged from the response to EDTA, and the renal tubular reabsorption of phosphate. In three patients serum parathyroid hormone concentrations, measured by radioimmunoassay, were in the upper part of the normal range. It is suggested that in patients with hypothyroidism the target cells in bone are less responsive to the effects of parathyroid hormone than normal; as a consequence parathyroid hormone secretion may be increased.