Both autoimmune and nonautoimmune hypothyroidism are associated with vitamin D deficiency, according to study results published in BMC Endocrine Disorders.

Given conflicting reports on the relationships between thyroid diseases and vitamin D deficiency, investigators aimed to evaluate vitamin D levels in patients with immune and nonimmune hypothyroidism in a cross-sectional case-control study.

A total of 633 patients with immune hypothyroidism (Hashimoto thyroiditis; 23.1% men) and 305 with nonimmune hypothyroidism (21.6% men) were recruited from an endocrinology clinic in Jahrom, Iran. An additional 200 healthy participants (24.5% men) were enrolled as controls.

Diagnosis of autoimmune Hashimoto thyroiditis was based on decreased thyroxine levels (<4.5 µg/dL), elevated thyrotropin concentrations (>3.6 mU/L), and the presence of either high serum thyroperoxidase (>40 U/mL) or thyroglobulin (>100 U/mL) antibodies. Vitamin D insufficiency was defined as concentrations <20 ng/mL.


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Vitamin D levels were higher in control participants compared with patients with Hashimoto thyroiditis (20.4 vs 13.22 ng/mL; P =.001) or nonautoimmune thyroiditis (16 ng/mL; P =.001). No significant difference was observed in vitamin D levels between patients with immune and nonimmune hypothyroidism (P =.923).

The group with vitamin D deficiency had a significantly higher number of thyroperoxidase antibody-positive individuals compared with the vitamin D-sufficient group (422 vs 195; P =.030), but no difference was observed in the number of thyroglobulin antibody-positive individuals between groups.

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There was an inverse correlation between vitamin D levels and thyroglobulin antibody levels in patients with Hashimoto thyroiditis (r=-0.261; P =.001). There was also a direct correlation between vitamin D and thyrotropin levels (r=0.108; P =.008). These associations were not observed in participants with nonimmune hypothyroidism or control patients.

“The results of the present research indicated that hypothyroidism patients with or without an immune base, deal with vitamin D deficiency (< 20 ng/mL) more than healthy people…[V]itamin D deficiency may have direct associations with thyroid gland function and indirectly may affect thyroid by modulating immune system,” the study authors concluded.

“[S]creening for vitamin D deficiency may be helpful in all hypothyroid patients,” they added.

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Reference

Ahi S, Dehdar MR, Hatami N. Vitamin D deficiency in non-autoimmune hypothyroidism: a case-control study. BMC Endocr Disord. 2020;20(1):41.