Hypothyroidism is usually not reversible when it is detected in a child at the age of 9. Symptoms can be controlled by medication. Thyroid hormones are vital to the physical and intellectual development of children. Hypothyroidism present in childhood, if left untreated, may result in slow growth, short stature, and mental retardation. Hypothyroidism in childhood is usually due to genetic factors. It should be diagnosed early and treated as soon as possible, and once diagnosed, it requires lifelong medication. The general treatment plan is to take oral levothyroxine sodium tablets to compensate for the insufficient secretion of endogenous thyroid hormones by supplementing exogenous thyroxine, thus ensuring normal physical and intellectual development. Once parents find that their children are short in stature compared with their peers, have poor learning ability, memory loss, etc., they should go to the hospital for examination and treatment in a timely manner to avoid delaying the condition.