The Calciferol Requirements of Patients with Surgical Hypoparathyroidism

Thirty patients with surgical hypoparathyroidism are presented. All received vitamin D therapy in the form of calciferol. Biochemical control, as defined by arbitrary criteria, was achieved in only nine patients for a total period of 26 patient-years. The mean controlling dose of calciferol was 2.12 mg/day; the mean dose producing hypercalcemia in 16 patients was 3.28 mg/day. No patient was controlled on less than 1.25 mg/day, and only two patients were controlled on a calciferol dose of 1.25 mg/day. Every patient receiving calciferol doses greater than 2.50 mg/day became hypercalcemic. A mechanism is suggested for the proximity between "controlling" and "intoxicating" doses of calciferol in hypoparathyroidism. The documented periods of hypercalcemia lasted 1 to 6 weeks after withdrawal of calciferol. No significant differences were found between the calciferol requirements of euthyroid and hypothyroid patients.