DOES PRE-OPERATIVE VITAMIN D DEFICIENCY PREDICT POSTOPERATIVE HYPOCALCEMIA AFTER THYROIDECTOMY?

OBJECTIVE: Postoperative hypocalcemia is frequent after total thyroidectomy. The role of pre-operative vitamin D levels in the pathogenesis of this condition has not been studied under the most current guidelines for evaluation of the role of vitamin D in calcium homeostasis. We hypothesized that patients who are vitamin D deficient (VDD) pre-operatively are more likely to suffer from postoperative hypocalcemia, thereby requiring prolonged hospitalization. METHODS: A retrospective chart review of patients undergoing total thyroidectomy at the University of New Mexico Hospital between 2005 and 2014 was performed. Patients who underwent intentional parathyroidectomy were excluded. The study included 30 patients who had a 25-hydroxyvitamin D levels obtained within 12 months before surgery. RESULTS: Twelve patients who were VDD (25-hydroxyvitamin D ≤20 ng/mL) were compared to 18 patients who did not have VDD (non-VDD; 25-hydroxyvitamin D >20 ng/mL). The mean nadir postoperative ionized calcium concentration was lower in the VDD group (0.99 ± 0.10 vs. 1.06 ± 0.06 mmol/L, P = .04) (reference range = 1.15-1.27 mmol/L), as was the postoperative concentration of phosphorus (3.48 ± 0.60 vs. 4.17 ± 0.84 mg/dL, P = .03). VDD patients had a longer length of stay (4.3 ± 4.4 vs. 1.7 ± 1.5 days, P = .03). Three patients in the VDD group required intravenous calcium for treatment of symptomatic hypocalcemia, but none of the non-VDD patients required this intervention (P = .054). CONCLUSION: Pre-operative vitamin D deficiency is associated with an increased risk of postoperative hypocalcemia and a prolonged length of stay in patients undergoing total thyroidectomy. Vitamin D replacement before thyroidectomy may improve postsurgical outcomes in VDD patients. ABBREVIATIONS: BMI = body mass index non-VDD = non-vitamin D deficient PTH = parathyroid hormone VDD = vitamin D deficient.