Abstract: ［Abstract］ Objective〖HTSS〗〓To investigate the 25 hydroxyvitamin D status in children with Hashimoto thyroiditis(HT) and the role of vitamin D in the pathogenesis of HT.
〖HTH〗〖WTHZ〗Methods〖HTSS〗〓Sixtyone children with HT in Shijiazhuang Han nationality were collected. The patients were divided into summerautumn group (JuneNovember) and winterspring group (December to May of the following year) according to the date of first visit, and ＜10 years old group and ≥10 years old group according to the age. Four milliliters of fasting venous blood samples were collected to test thyrotropin(TSH), total thyroxin(TT4), free thyroxine(FT4), total triiodothyronine(TT3), free triiodothyronine(FT3), thyroid peroxidase antibody(TPOAb), thyroglobulin(TG), thyroglobulin antibody(TGAb) and 25 hydroxyvitamin D(25OHD) level. The lengths, widths and thicknesses of the right and left lobes of the thyroid were measured by ultrasound and the volume of thyroid was calculated, and the iodine in the morning midstream urine was measured by electrochemical method.
〖HTH〗〖WTHZ〗Results〖HTSS〗〓The level of 25OHD in 61 children with HT was （47.50±1788） nmol/L, 15 cases(24.59%) were deficient, 19 cases(31.15%) were insufficient  and 27 cases(44.26%) were sufficient. The levels of 25OHD were （55.15±18.61） nmol/L and （42.55±15.73） nmol/L in summerautumn group and winterspring group respectively. The summerautumn group were higher than the winterspring group(P＜005). There was no difference in thyroid related laboratory parameters between the two groups. The levels of 25OHD were （49.14±18.15） nmol/L and （45.81±17.75） nmol/L in groups of<10 years old and≥10 years old respectively. There was no significant difference between the two groups(P＞005). There was no difference in thyroid related laboratory parameters between the two groups either. Serum 25OHD level was negatively correlated with TG(rs=-0.348, P=0006), and there was no correlation between 25OHD and thyroid volume, TSH, TT4, FT4, TT3, FT3, TGAb and morning midstream urinary iodine(P＞005).
〖HTH〗〖WTHZ〗Conclusion〖HTSS〗〓The serum 25OHD level in children with HT was not significantly decreased, and the seasonal changes were still present. The serum 25OHD level may not affect the laboratory and clinical parameters of children with HT.

Key words: Hashimoto disease, vitamin D, child