Decreased calcitriol requirement during pregnancy and lactation with a window of increased requirement immediately post partum.

OBJECTIVE

To describe the changes in calcium and calcitriol requirements during pregnancy and lactation in a patient with hypoparathyroidism due to autosomal dominant hypocalcemia.

METHODS

We summarize the clinical presentation and treatment of the patient and review the pertinent literature.

RESULTS

Calcitriol requirements disappeared during pregnancy in a 34-year-old woman with autosomal dominant hypoparathyroidism secondary to an activating mutation in the calcium-sensing receptor gene. Within hours after delivery, her serum calcium concentration dropped to 4.7 mg/dL (albumin, 3.2 g/dL), and she required intravenous calcium and reinstitution of calcitriol. When lactation began a few days later, her calcitriol requirement again disappeared. As has occasionally been described in the literature, this patient with hypoparathyroidism required no calcitriol during late pregnancy and lactation to maintain a normal serum calcium level.

CONCLUSIONS

To our knowledge, this is the first reported case documenting a period of time between pregnancy and lactation when calcitriol requirements reappeared, likely due to a parathyroid hormone-related protein "window" between delivery, when placental production of parathyroid hormone-related protein stops, and lactation, when mammary gland production begins.