Role of Follicular T Cells in Hashimoto's Thyroiditis

Inclusion Criteria: \- The study will include 45 Hashimoto's patients attending the out clinics of Endocrinology Department of Assiut university hospital. In addition, 45 healthy blood donors will be included as controls. The diagnosis of hashimoto's thyroiditis will be determined according to the criteria of American Thyroid Association; * Having symptoms of hypothyroidism, and a blood test shows an underactive thyroid gland \[an elevated thyroid stimulating hormone (TSH) level with or without a low thyroid hormone (free T4 or total T4) level\]. * have elevated thyroid antibody levels. * ultrasound examination demonstrating characteristic heterogeneous echotexture. * results of thyroid fine needle aspiration (FNA) examinations meeting HT cytology diagnostic criteria. Exclusion Criteria: * -We should exclude other causes of thyroiditis, such as De Quervain's thyroiditis, Riedel's thyroiditis, and suppurative thyroiditis and also exclude other autoimmune diseases for example; type1 diabetes\&Rheumatoid arthritis,and other diseases which cause hypothyroidism as carcinoma and surgery.