CD4 and Hashimoto thyroiditis: In Graves’ disease, lymphocyte infiltration is not severe and mainly CD4 + T helper 2 cells take the lead.[4] Although there are many studies reporting that autoimmune thyroid diseases may be associated with Vitamin D deficiency, there are also studies reporting that there is no relationship, and this is still a controversial issue.[1,6,10] In studies evaluating the correlation between Vitamin D and Hashimoto thyroiditis to date, the diagnosis of Hashimoto thyroiditis was generally evaluated according to TPO-Ab positivity and ultrasonographic findings.