A 12-year-old boy may have hypothyroidism. The full name of hypothyroidism is hypothyroidism, which is a generalized low metabolic syndrome caused mainly by hypothyroid hormonemia or thyroid hormone resistance due to various reasons. Hypothyroidism can occur in 12-year-old boys when there is autoimmune damage, destruction of the thyroid gland, iodine excess or deficiency, genetic mutation, pituitary or hypothalamic pathology. Hypothyroidism can cause chills and loss of appetite in the early stages, or no obvious symptoms. In severe cases, it can lead to pericardial effusion, heart failure and other serious illnesses, which can affect children’s health. 12-year-old children with hypothyroidism should go to the hospital in a timely manner, follow the doctor’s instructions for treatment, to avoid delaying the condition.