Vitamin D treatment in primary hyperparathyroidism: a randomized placebo controlled trial.

Single-center, investigator-initiated, double-blind, randomized, placebo-controlled, parallel-group trial at Aarhus University Hospital in Denmark. Adults with primary hyperparathyroidism and vitamin D insufficiency were randomized; for the vitamin D group, 20 participants were randomized and 20 were analyzed/completed.

Vitamin D3 (cholecalciferol) was given orally at 70 g (2800 IU) daily for 52 weeks, covering 6 months before and 6 months after parathyroidectomy. The active intervention was compared with placebo in a double-blind randomized design.

High-dose vitamin D3 was safe and improved vitamin D status and PTH control in patients with primary hyperparathyroidism. In the vitamin D group, 25OHD rose from 50.2 to 94.2 nmol/L preoperatively (P < .001), PTH fell by 17% with an absolute difference of 2.4 ± 1.2 pmol/L, and 1,25(OH)2D increased from 98 to 127 pmol/L (30%, P = .008). Bone resorption improved preoperatively, with CTx decreasing 22% (P < .005) and lumbar spine BMD increasing 2.5% (P = .01) versus placebo; after surgery, PTH remained lower in the vitamin D group (P = .04), while calcium levels and renal function were unaffected. Two serious adverse events and 13 adverse events occurred overall, and none were attributed to study medication.

The trial was small, with only 20 participants per active arm analyzed/completed, and it was conducted at a single center in Denmark, limiting generalizability. Ethnicity was not reported, and several outcomes were most clearly demonstrated within the vitamin D arm rather than as large between-group differences after surgery.