Effect of vitamin D3 on thyroid function and de-iodinase 2 expression in diabetic rats

Objective: This study aimed to assess the effect of vitamin D-3 administration to diabetic rats on thyroid profile and deiodinase 2 (D2). Methods: Thirty male Wistar rats were included into three groups; control, streptozotocin-induced diabetic and diabetic supplemented with vitamin D-3 groups. Ten weeks later, serum levels of free T-4, free T-3 and TSH were measured. Tissue homogenates from liver, kidney, muscle, femur bone, heart and brain were obtained and assessed for D2 mRNA. Results: Diabetic rats demonstrated significant increase in free T-4 and significant decrease in free T-3. These changes were ameliorated by vitamin D-3 administration. D2 mRNA was significantly reduced in all tissue homogenates obtained from diabetic rats, while vitamin D-3 treatment significantly enhanced D2 in liver and brain homogenates. Conclusion: Diabetes mellitus inhibited peripheral conversion of T-4 into T-3 secondary to reduction in D2 expression. Vitamin D-3 greatly corrected the alterations in thyroid profile and D2 expression.