The Relationship between Serum Vitamin D Levels and Thyroid Functions in Patients with Hashimoto’s Thyroiditis from Saudi Arabia

Abstract

Hashimoto’s thyroiditis (HT) is a chronic devastating autoimmune disorder of the thyroid gland, which develops due to environmental and genetic predispositions. Various studies have explored the role of 25(OH)-D deficiency in HT. Although vitamin D supplementation is suggested to improve thyroid functions, the mechanism of action of vitamin D on thyroid hormones remains unclear. The objective of the present study was to determine serum concentrations of thyroid hormones, serum thyroid antibodies, and serum 25(OH)-D and underscore the association of vitamin D with thyroid function in HT. A cross-sectional study comprising 150 subjects, including 80 HT cases and 70 healthy controls was carried out. The serum thyroid hormone concentrations (FT4, TSH), serum thyroid antibodies (anti-TPO, anti-Tg), serum 25(OH)-D, serum ferritin, blood hematocrit, and mean cell volume (MCV) were measured. Results showed that serum TSH, anti-Tg, and anti-TPO were significantly increased in HT cases than in the healthy controls, while serum FT4, 25(OH)-D and ferritin were significantly reduced (p <0.0001). A negative correlation between serum vitamin D with anti-TPO and a positive correlation with FT4 and ferritin (p <0.05) was observed. The results indicated that reduced serum levels of vitamin D are associated with higher serum anti-TPO and lower serum FT4 and ferritin levels in HT patients.