The causes of thyroid enlargement in children include physiologic factors such as iodine deficiency and pathologic factors such as various thyroid diseases. 1. Physiological factors: iodine deficiency can cause diffuse goiter leading to thyroid enlargement. At the same time, children’s thyroid function is relatively active, and relatively high thyroxine can also cause mild goiter, which usually shrinks on its own in adulthood. 2. Pathological factors: These include various thyroid diseases, such as primary hyperthyroidism, secondary hyperthyroidism, high-functioning adenoma, subacute thyroiditis, thyroid adenoma and thyroid cancer. Pathological goiter is often accompanied by thyroid hormone abnormalities, localized pain in the thyroid gland and other symptoms. In case of thyroid enlargement, it is recommended to consult a doctor for thyroxine measurement, thyroid ultrasound and other related examinations.