The Serum Levels Assessment of IGG-4 in Patients with Autoimmune Hypothyroidism, and Its Relationship with Anti-TPO Antibody

Introduction: Hypothyroidism is one of the most common endocrine disorders. In many countries, autoimmune disorders are the most common cause of hypothyroidism. Regarding the high prevalence of hypothyroidism in the Iranian population, this study was performed to evaluate the serum levels of IGG-4 in patients diagnosed with autoimmune hypothyroidism and to find its possible relationship with anti-thyroid peroxidase antibody (Anti-TPO).Methods & Materials: In this study, patients (new cases) who had referred to Endocrine and Thyroid Clinics of Ghaem Educational Hospital, Mashhad, Iran, and diagnosed with autoimmune hypothyroidism between the years of 2017 until 2019 were enrolled. Initially, the demographic information of each subject was gathered and then they underwent a physical examination by an expert endocrinologist. Venous blood sample was taken from each subject to analyze the serum levels of IGG-4, Free T4, TSH, and Anti-TPO antibody. Participants were divided into two groups based on their serum level of IGG-4, where group 1 consisted of subjects with serum IGG-4 levels above 135mg/dL, and group 2 consisted of subjects with serum IGG-4 levels below 135mg/dL (non-IGG-4 related autoimmune hypothyroidism).Results: Autoimmune hypothyroidism was more common in females (79.55% females compared with 20.45% males, the mean age was 36.89±7.97 years). The mean serum level of IGG-4 in all subjects with autoimmune thyroid disease was 86.11±96.18 mg/dL. Seven patients (15.9%) had elevated serum levels of total IGG-4 (IGG-4> 135mg/dl, the mean was 276.87±111.64 mg/dL). The mean serum level of TSH, T4 and of Anti-TPO antibody was 23.10±14.42 mIU/L, 0.84±0.44 µg/dL, and 431.06±233.57 IU/mL respectively. There was no relationship between age, IGG-4, Anti-TPO antibody, and TSH. A positive correlation was found between the Anti-TPO antibody and Free T4 in females (p=0.002, r=0.496). Also, a reverse correlation was observed between Free T4 and TSH (p=0.033, r = - 0.322).Conclusion: Autoimmune hypothyroidism is significantly more common in females. Our results showed that about 15% of hypothyroid autoimmune patients are IGG-4-related (IGG-4> 135mg/dl). There is no correlation between the serum levels of IGG-4 and Anti-TPO antibody.