Hypercalcemia in a woman with hypoparathyroidism associated with increased parathyroid hormone-related protein during lactation.

OBJECTIVE

To report a case of postpartum hypercalcemia in a woman with hypoparathyroidism associated with increased serum concentrations of parathyroid hormone-related protein (PTHrP) during lactation.

METHODS

The clinical and laboratory data for our patient and the related literature are reviewed.

RESULTS

A 35-year-old woman with long-standing surgical hypoparathyroidism treated with dihydrotachysterol and calcium carbonate gave birth to a healthy boy at 40 weeks of gestation and began lactating normally. Two and a half weeks later, hypercalcemia developed in association with nausea, vomiting, and myalgias. Subsequently, an increased serum PTHrP concentration was noted. After saline diuresis and corticosteroid therapy to correct the hypercalcemia, a normal serum calcium level was maintained without vitamin D preparations or calcium supplements until the 12th postpartum week, when hypocalcemia reappeared. The serum PTHrP level was no longer increased, and treatment with calcitriol and calcium carbonate was resumed. Subsequent serum calcium concentrations have been normal.

CONCLUSIONS

This case suggests that PTHrP stimulation of the parathyroid hormone-PTHrP receptor during lactation may compensate for the absence of parathyroid hormone in lactating women with hypoparathyroidism and that treatment with pharmacologic doses of vitamin D preparations during the postpartum period may result in hypercalcemia.