Relationship of Vitamin D Deficiency and Intraoperative Parathyroid Hormone Elevation in Completion and Total Thyroidectomy.

Objective: To quantify how frequently intraoperative parathyroid hormone levels increase during thyroid surgery and to explore a possible relationship between secondary hyperparathyroidism due to vitamin D deficiency and elevation in intraoperative parathyroid hormone.

Study Design: Case series with chart review.

Setting: Tertiary academic center.

Subjects And Methods: A total of 428 consecutive patients undergoing completion and total thyroidectomy by the senior author over a 7-year period were included for analysis. All patients had baseline and postexcision intraoperative parathyroid hormone levels as well as vitamin D levels from the same laboratory. Institute of Medicine criteria were employed for vitamin D stratification (>30, normal; 20-29.9, insufficient; <20, deficient) . Other data analyzed include sex, age, neck dissection status, and parathyroid autotransplantation.

Results: A total of 118 patients (27.6%) had an intraoperative parathyroid hormone elevation above baseline. Patients with vitamin D deficiency were significantly more likely to experience hormone elevation ( P = .04). When parathyroid hormone rose, it did so by a mean 32.1 pg/mL. Patients with vitamin D deficiency demonstrated significantly larger hormone increases ( P = .03).

Conclusion: Elevation in intraoperative parathyroid hormone levels above baseline after completion and total thyroidectomy occurs in over one-fourth of cases and is significantly associated with vitamin D deficiency. This study is the first to report this observation. We hypothesize that vitamin D deficiency in these patients may create a subclinical secondary hyperparathyroidism that leads to intraoperative parathyroid hormone elevation when the glands are manipulated. Additional studies will be needed to explore this physiologic mechanism and its clinical significance.