Diagnosis and treatment of hypothyroidism in children

Hypothyroidism represents one of the most common endocrine disorders in infancy and childhood. Screening programs of newborns report that congenital hypothyroidism occurs in approximately one in 4000 newborn infants. Studies of school age children report that 1.2% are positive for antithyroid antibodies. Acquired hypothyroidism caused by chronic lymphocytic thyroiditis is estimated to occur in from one in 500 to one in 1000 children. At the cellular level, thyroid hormone regulates protein synthesis and cell growth and differentiation. Thyroid hormone plays a critical role in normal growth and development, particularly during the first three years of life. Thyroid hormone is crucial for normal development of the central nervous system, and untreated congenital hypothyroidism will result in mental retardation and other neurologic sequelae such as incoordination, abnormal muscle tone, short attention span, learning disorders, and deafness. A major advance in the prevention of brain damage resulting from congenital hypothyroidism has been the development of screening programs of newborns that allow detection and treatment within the first month of life before clinical manifestations are apparent. Other physiologic effects of thyroid hormone deficiency include decreases in oxygen consumption, metabolic rate, nerve conduction, cardiac contractility, and muscle capacity. Children with acquired hypothyroidism most commonly have a decrease in growth velocity, short stature, sluggishness, cold intolerance, and a decrease in school performance. If hypothyroidism develops during adolescence, delayed puberty is also a feature. A goiter is commonly present. All of these changes are reversible with treatment with thyroid hormone.