Enlarged thyroid refers to the increase in volume and shape of the thyroid gland. Common causes include iodine deficiency, drug-induced, thyroid diseases, etc. Iodine deficiency is the raw material for thyroid hormone synthesis. 1. Iodine deficiency: Iodine is the raw material for the synthesis of thyroid hormone, iodine deficiency leads to the body can not synthesize thyroid hormone, negative feedback to promote the secretion of thyroid stimulating hormone, which acts on the thyroid gland and leads to goiter. 2. Drugs: thiocyanate, perchlorate, large doses of iodine and other substances can inhibit the synthesis of thyroid hormones, resulting in goiter. 3. Thyroid disease: when certain factors disturb or destroy the normal balance of the thyroid gland, prompting the pituitary gland to secrete too much thyroid-stimulating hormone (TSH), often causing goiter. Hashimoto’s thyroiditis, subacute thyroiditis can have goiter; thyroid tumor can also have goiter. People with an enlarged thyroid should go to the hospital to find out the cause and treat it under the guidance of a doctor.