Reduced calcitriol requirements for treating hypoparathyroidism during lactation. A case report.

We reduced the dose of calcitriol from 0.75 to 0.25 microgram/d to maintain low normal serum calcium levels in a hypoparathyroid woman during lactation. Calcitriol requirements quickly returned to 0.75 microgram/d when she discontinued breast-feeding. In her previous pregnancy, failure to reduce the dose of calcitriol resulted in serious hypercalcemia 11 days after she began breast-feeding. The changing requirement for calcitriol in our patient related directly to the falling level of estradiol. Although the cause or causes of diminished calcitriol requirements in hypoparathyroid women during lactation remains unclear, increased bone resorption promoted by low plasma estrogen levels may be an important mechanism. We conclude that the dose of calcitriol should be reduced during lactation and that both the hypoparathyroid mother and her infant should be carefully monitored to detect abnormal serum calcium levels.