The effect of preoperative vitamin D values on hypocalcemia after total thyroidectomy.

Objectives: Hypocalcemia is a common complication following thyroidectomy. Vitamin D plays a critical role in calcium regulation. This study aimed to investigate the relation between preoperative vitamin D levels and postoperative hypocalcemia. Material and Methods: We conducted a retrospective analysis of 899 patients who underwent total thyroidectomy at our center between 2015 and 2020 due to multinodular goiter, atypia of undetermined significance, follicular lesions, and follicular neoplasia. Patients were excluded if they had a history of thyroid surgery, Graves' disease, renal failure, incidental parathyroidectomy, or received calcium or vitamin D supplementation before surgery. The patients were divided into two groups based on their preoperative vitamin D levels: Group 1 (n= 240) with levels <10 ng/mL, and Group 2 (n= 659) with levels ≥10 ng/mL. Demographic characteristics and pre- and postoperative laboratory values were compared between the groups. Results: The female-to-male ratio was 3.22, with an average vitamin D level of 18.94 ± 13.28 ng/mL. Vitamin D levels were significantly lower in women compared to men (p= 0.001). In Group 1, the rates of asymptomatic and symptomatic postoperative hypocalcemia were 17.1% and 6.7%, respectively; while in Group 2, these rates were 11.2% and 3.2% (p= 0.020). The average preoperative vitamin D level was 14.79 ± 9.4 ng/mL in patients who developed hypocalcemia and 19.12 ± 13.4 ng/mL in those who remained normocalcemic, with this difference being statistically significant (p= 0.026). Conclusion: In our study, we found that preoperative vitamin D level below 10 ng/mL is associated with increased risk of hypocalcemia following thyroidectomy.