Background: Although some studies have reported that preoperative vitamin D deficiency (VDD) is a risk factor for hypocalcemia after total thyroidectomy (TT) in patients with nontoxic multinodular goiter or Graves' disease, the association between VDD and postoperative hypocalcemia in thyroid cancer patients undergoing TT plus central compartment neck dissection (CCND) remains unclear. This study evaluated whether preoperative VDD was associated with postoperative symptomatic hypocalcemia.
Materials and methods: Data were collected prospectively between September 2012 and May 2013. A total of 267 consecutive thyroid cancer patients who underwent TT with CCND were analyzed. Patients were divided into two groups--VDD or non-VDD--by preoperative vitamin D level of <10 or ≥10 ng/mL. Symptomatic hypocalcemia was defined as serum calcium <8.2 mg/dL and symptoms or signs of hypocalcemia. The rates of postoperative symptomatic hypocalcemia and clinicopathological features were compared between the two patient groups.
Results: The rate of postoperative symptomatic hypocalcemia was higher in the VDD group than in the non-VDD group (43.8% vs. 30.4%, p=0.043). By logistic regression analysis, predictive factors for postoperative symptomatic hypocalcemia included a preoperative vitamin D level of <10 ng/mL (p=0.007; odds ratio=3.00). In patients who had postoperative intact parathyroid hormone (iPTH) levels <15 pg/mL, symptomatic hypocalcemia was more common in the VDD group than in the non-VDD group (77.5% vs. 53.2%, p=0.008). The findings show that a preoperative vitamin D threshold level of >20 ng/mL reduced the risk of symptomatic hypocalcemia by 72% when compared with patients with VDD (p=0.003).
Conclusion: VDD is significantly associated with postoperative symptomatic hypocalcemia in thyroid cancer patients undergoing TT plus CCND. VDD was predictive for symptomatic hypocalcemia when patients had postoperative serum iPTH levels <15 pg/mL. Thus, preoperative supplementation with oral vitamin D should be considered to minimize postoperative symptomatic hypocalcemia.