The thyroid gland is an endocrine gland composed of two lobes which are connected by the isthmus. Thyroid hormones are triiodothyronine and tetraiodothyronine. Thyroid gland is under the control of the pituitary gland and its hormone TSH. Hypothyroidism describes decreased thyroid function and term hyperthyroidism describes a condition of excessive production of thyroid hormones.Conatal hypothyroidism may occur sporadically or familially. Usually the diagnosis of hypothyroidism was made too late, and for this reason, neonatal screening for congenital hypothyroidism was introduced in a large number of countries. Therapy is started immediately with a full dose of L-thyroxine. The most common cause of acquired hypothyroidism is chronic autoimmune thyroiditis (Hashimoto's or atrophic). In children with hypothyroidism, the first and most common manifestation is growth retardation. Iti s treated with levothyroxine substitution therapy. Hyperthyroidism most commonly occurs in the newborn due to transplacental transmission of maternal TSH-receptor stimulating antibodies. In addition to early diagnosis, early propylthiouracil therapy is required. Graves' disease is an autoimmune disease of the thyroid gland caused by TSH-receptor stimulating autoantibodies. Hyperthyroidism in childhood has a significant impact on growth and pubertal development. Therapy for Graves' disease in children and adolescents are antithyroid drugs, radioactive iodine, or thyroidectomy. Thyroid tumors are not common condition in children and adolescents, but should be suspected whenever a physical examination reveals a solitary nodule. The therapy is surgical, and if necessary, radioactive iodine is then used for therapeutic purposes.