Assessment of Pre-Operative Vitamin D Serum Levels in Thyroid Cancer Patients

Abstract Objective To investigate the relationship between vitamin D levels and thyroid cancer (TC) incidence and the effect of pre-operative vitamin D supplementation. Methods This retrospective case-control study was conducted on patients who underwent thyroidectomy at King Abdulaziz Medical City from January 2016 to January 2022. Their pre-operative vitamin D serum levels and histopathology of resected thyroid nodule (TN) were evaluated. Multivariable conditional logistic regression was computed to determine the relationship between serum 25(OH) D level and TC. Results A total of 633 patients were included in the study, with 325 malignant TN cases and 308 benign TN cases as control. TC group had significantly higher serum 25(OH) D levels than the controls (51.12 nmol/L vs. 46.17 nmol/L, p-value = 0.037). However, there was no significant difference between the groups on serum 25(OH) D level, once categorised into deficient, inadequate, normal, or high. Patients on Vitamin D supplements had a lower incidence of TC (45.5%) than those not on Vitamin D supplements (57.5%), with a significant (p-value = 0.003). In multivariable regression models, patients who took Vitamin D supplements had a 37% lower risk of having TC than those who did not (OR = 0.634; 95% CI = 0.460–0.873). Conclusion There was no significant correlation between Vitamin D deficiency and TC. However, patients on Vitamin D supplements had a lower risk of developing TC than those who had not. Further prospective studies are necessary to clarify the function of this factor.