Low Vitamin D and Risk of Post‐thyroidectomy Hypocalcemia

Abstract

Objective: 1) Determine if low vitamin D reduces risk of post-thyroidectomy hypocalcemia. 2) Verify if this is an independent effect. Method: Retrospective study of 139 total thyroidectomy patients (October 2009-October 2011) at a McGill University teaching hospital. Preoperative 25-hydroxy-vitamin D (25OHD), calcium, and PTH were measured. Patients were assessed for postoperative hypocalcemia. Low vitamin D (LVD) was defined as 25OHD ≤70 nmol/L (28 ng/mL) and optimal vitamin D (OVD) was defined as 25OHD >70 nmol/L (28 ng/mL). Results: Hypocalcemia occurred in 3.2% (2 of 62) patients with LVD and 10.4% (8 of 77) patients with OVD (OR 0.2875, P = .124). No patients with vitamin D deficiency (VDD), defined as 25OHD ≤35 nmol/L (14 ng/mL), developed hypocalcemia. Univariate analysis did not show age, sex, malignancy, presence of thyroiditis, number of preserved parathyroids, parathyroid autotransplantation, preoperative PTH, or preoperative calcium to be significantly predictive. Multivariate analysis confirmed no confounding factors in vitamin D analysis, but also did not show any independent risk factors. Fisher analysis comparing total versus completion thyroidectomy was marginally significant ( P = .064) for predicting hypocalcemia. Conclusion: Transient hypocalcemia appears to occur less frequently in patients with VDD, however in our limited study we were unable to elucidate whether this was significant. Future study observing a larger population and excluding completion thyroidectomy patients may help to clarify whether VDD impacts risk for hypocalcemia.