Vitamin D Treatment in Primary Hyperparathyroidism: A Randomized Placebo Controlled Trial

Context: Low 25-hydroxyvitamin D levels are common in patients with primary hyperparathyroidism (PHPT) and associated with higher PTH levels and hungry bone syndrome after parathyroidectomy (PTX). However, concerns have been raised about the safety of vitamin D supplementation in PHPT. Objective: We aimed to assess safety and effects on calcium homeostasis and bone metabolism of supplementation with high doses of vitamin D in PHPT patients. Design, Setting: This was an investigator-initiated double-blind, randomized, placebo-controlled, parallel-group trial from a single center. Patients: Forty-six PHPT patients were recruited, with a mean age of 58 (range 29-77) years, and 35 (76%) were women. Interventions: Intervention included daily supplementation with 70 mu g (2800 IU) cholecalciferol or identical placebo for 52 weeks. Treatment was administered 26 weeks before PTX and continued for 26 weeks after PTX. Main Outcome Measures: PTH, calcium homeostasis, and bone metabolism were evaluated. Results: Preoperatively, 25-hydroxyvitamin D increased from 50 to 94 nmol/L in the treatment group and decreased from 57 to 52 nmol/L in the placebo group (P < .001). Compared with placebo, vitamin D decreased PTH significantly by 17% before PTX (P = .01), increased lumbar spine bone mineral density by 2.5% (P = .01), and decreased C-terminal beta-CrossLaps by 22% (P < .005). The trabecular bone score did not change in response to treatment, but improved after PTX. Postoperatively, PTH remained lower in the cholecalciferol group compared with the placebo group (P = .04). Plasma creatinine and plasma and urinary calcium did not differ between groups. Conclusions: Daily supplementation with a high vitamin D dose safely improves vitamin D status and decreases PTH in PHPT patients. The vitamin D treatment is accompanied by reduced bone resorption and improved bone mineral density before operation.