Treating vitamin D insufficiency in primary hyperparathyroidism: a cautionary tale

Vitamin D deficiency is a poorly recognized pandemic and can be associated with primary hyperparathyroidism, which is not infrequently found in the general population. No formal guidelines exist to guide therapy for suboptimal Vitamin D status in patients with hyperparathyroidism. However, there are many potential benefits to achieving a Vitamin D replete state before parathyroid surgery. Previous reports have indicated that Vitamin D status can be improved without adverse effects in hyperparathyroidism. We report accentuation of hypercalcemia and hypercalciuria with Vitamin D treatment (weekly 50,000 IU ergocalciferol x 8 weeks) in a 64-year-old Caucasian male veteran with primary hyperparathyroidism, osteoporosis and Vitamin D insufficiency. The exacerbation of hypercalcemia and hypercalciuria resolved with cessation of Vitamin D therapy. We propose that clinicians consider using modest doses of Vitamin D such as 1,000 IU daily for replacement in patients with hyperparathyroidism and Vitamin D deficiency. We recommend that serum and urine calcium be monitored if such treatment is implemented.