Renal Function in Treated Hypoparathyroidism a Possible Direct Nephrotoxic Effect of Vitamin D

Abstract

Vitamin D* intoxication is a well known hazard in the treatment of hypoparathyroidism. Impaired renal function in a patient receiving vitamin D is usually attributed to hypercalcemia (1), but even in the absence of this complication, the metabolic abnormalities of parathyroid hormone (PTH) deficiency are incompletely corrected by vitamin D. The plasma phosphate usually falls to within the normal range, but the mean value remains elevated. PTH increases the tubular reabsorption of calcium; vitamin D may have a similar effect (2), but normocalcemia can often only be maintained in the absence of PTH at the expense of hypercalciuria (3). Either persistent hyperphosphatemia or hypercalciuria might conceivably result in renal injury. Finally, as in the rat, vitamin D itself may have a direct nephrotoxic effect (4). In view of these uncertainties, a detailed study was undertaken of renal function in vitamin D treated hypoparathyroidism.