Analysis of vitamin D nutritional status and disease risk factors in patients with subacute thyroiditis

Background: Vitamin D (VD) deficiency has become a global public health problem, and published studies have demonstrated that patients with subacute thyroiditis (SAT) have worse VD nutritional status and that VD supplementation may alleviate thyroid-related diseases by fighting against infections and mediating autoimmunity. Objectives: This study explored the correlation between serum VD levels and the risk and extent of disease in patients with SAT. Design: A case-control study. Methods: We included patients with SAT diagnosed at the First People’s Hospital of Jining City between September 2021 and September 2023 and a healthy population during the same period. We collected clinical and laboratory data to determine differences in VD levels between the two populations and identify risk factors for the onset and extent of SAT. Results: The 25(OH)D level of SAT patients was significantly lower than that of the healthy population ( p < 0.05). Multifactorial logistic regression analysis showed that low 25(OH)D level, low body mass index (BMI), elevated leukocytes, and low lymphocyte count were independent risk factors for SAT. No significant difference was noted in VD levels between patients with mild SAT and those with moderately severe SAT ( p > 0.05). Additionally, fever, thyroid tenderness, high BMI, and elevated free thyroxine (FT4) were independent risk factors for SAT severity; serum 25(OH)D levels were positively correlated with FT4/FT3 levels in SAT patients. Conclusion: VD levels are lower in patients with SAT than in healthy controls, and low VD levels increase SAT risk. Although VD levels are not related to SAT severity, adequate VD inhibits the conversion of FT4 to FT3, likely playing a protective role in SAT development.