ODP464 Association between preoperative vitamin D insufficiency and postoperative symptomatic hypocalcemia in patients with thyroid cancer

BACKGROUND: It is controversial whether vitamin D insufficiency (VDI) increases the risk of postoperative hypocalcemia and decreases the predictive power of parathyroid hormone (PTH) for postoperative hypocalcemia in patients undergoing total thyroidectomy (TT). Here, we investigated the role of VDI in the development of postoperative symptomatic hypocalcemia and assessed its effect on the predictive power of PTH as a marker for postoperative symptomatic hypocalcemia in thyroid cancer patients who underwent TT plus central compartment neck dissection (CCND). METHODS: All consecutive differentiated thyroid cancer patients who underwent TT plus CCND between January 2017 and December 2020 at a single tertiary referral hospital were retrospectively reviewed. Patients were divided into two groups according to their preoperative 25-hydroxyvitamin D (25(OH)D) levels (< 20 vs. ≥ 20 ng/ml). Postoperative symptomatic hypocalcemia was defined as ionized calcium < 2.2 mEq/l on postoperative day 1 and positive symptoms or signs of hypocalcemia. The effects of exposure on postoperative symptomatic hypocalcemia were analyzed using a multivariate logistic regression model. RESULTS: The incidence of postoperative symptomatic hypocalcemia was comparable between patients with and without VDI (P= 0.252). Preoperative VDI was not associated with the development of postoperative symptomatic hypocalcemia (OR = 1. 07, 95% CI 0.73 to 1.56, P= 0.744). Postoperative hypoparathyroidism (iPTH < 15 pg/ml) was associated with the development of postoperative symptomatic hypocalcemia in both VDI and non-VDI patients (OR = 6.78, 95% CI 3.88 to 11.85, P< 0. 001 and OR = 9.68, 95% CI 3.86 to 24.28, P< 0. 001, respectively). CONCLUSIONS: VDI did not predict postoperative symptomatic hypocalcemia after TT plus CCND in thyroid cancer patients and did not influence the predictive power of postoperative PTH for postoperative symptomatic hypocalcemia. Therefore, prophylactic calcium and vitamin D supplementation in patients with VDI should be carefully considered in thyroid cancer patients. Presentation: No date and time listed