Chronic inflammation of the thyroid gland due to autoimmune factors causing lymphocytic infiltration of the gland is the most common cause of primary hypothyroidism. The prevalence is higher in women than in men (8:1), the incidence increases with age, and a family history of thyroid disease is common. Histological studies reveal extensive lymphocytic infiltration of the thyroid gland with lymphoid follicles. Symptoms and signs Patients complain of a painless enlarged thyroid with a swollen throat. Examination reveals a painless enlarged or nodular thyroid that is firm and harder than a normal thyroid. When first seen, many patients have pre-existing hypothyroidism, other forms of autoimmune disease are common, including pernicious anemia, rheumatoid arthritis, SLE, dry syndrome, and other autoimmune endocrinopathies can co-exist, including Addison’s disease (adrenocortical insufficiency), hypoparathyroidism, insulin-dependent diabetes mellitus, Schmidt syndrome is Addison’s disease and secondary to bradycardia. The incidence of hypothyroid thyroid cancer can be increased in this disease, especially papillary carcinoma and thyroid lymphoma. Diagnosis Early laboratory tests include increased titers of normal T3, T4 and thyroid peroxidase antibodies and, less commonly, thyroglobulin antibodies, and increased radioiodine uptake by the thyroid gland, most often due to impaired thyroid iodination with persistent iodine uptake by the thyroid gland, and later development of hypothyroidism with decreased T4, decreased thyroid radioiodine uptake and increased TSH. Treatment Hashimoto’s thyroiditis requires lifelong thyroid hormone replacement therapy to reduce hypertrophy and treat hypothyroidism, which is occasionally transient. The average T4 dose of replacement therapy is 75 to 150 μg/d. 1. Thyroid tablets or sodium thyroxine are given for treatment; 2. Antithyroid drugs and thyroid tablets may be given simultaneously in cases with hyperthyroidism; 3. Short-term application of corticosteroid therapy may be given in cases with obvious enlargement of the thyroid gland or with symptoms of compression; 4. Surgery may be considered in cases with obvious symptoms of compression that have failed with the above treatment.