Study on the clinical features of Hashimoto′s thyroiditis with elevated serum IgG4

Abstract

Objective To investigate the clinical features of Hashimoto′s thyroiditis(HT) with elevated serum IgG4 levels and to guide the clinical practice. Methods Serum IgG4 concentrations were detected in patients with HT by nephelometric immunoassay. These patients were classified into two groups according to the IgG4 levels: positive group(IgG4≥1.35 g/L), and negative group(IgG4<1.35 g/L). The clinical characteristics of these two groups, including age, gender, medical history, serological features, and ultrasound were compared. Results Nine out of 111 patients with HT were positive with IgG4(8.11%), all of them were women. There was no significant difference in gender, age, BMI, dose of levothyroxine administration, FT3, FT4, and TSH levels between the two groups. The volume of thyroid in positive group was larger than that in negative group [57.81(38.36, 74.93) ml vs 25.07(18.48, 42.14) ml, P=0.015], and the level of thyroglobulin antibodies(TgAb; P=0.011) and thyroid peroxidase antibodies(TPOAb; P=0.025) in positive group were also significantly higher than those in negative group. Moreover, the positive group had a slightly higher risk of PTC than that of negative group(11.1% vs 2.94%, P=0.290), though the difference was not significant. Correlation analysis showed that IgG4 was positively associated with TgAb, TPOAb, and thyroid volume. Conclusions The levels of TgAb and TPOAb are higher, the volume of thyroid gland is greater, and the risk of PTC with lymph node metastasis is more frequent in HT patients with elevated serum IgG4. For HT patient with elevated serum IgG4, their thyroid function and morphology should be more closely monitored. Key words: IgG4; Hashimoto′s thyroiditis; Papillary thyroid carcinoma