Hypothyroidism in children
Deficiency of thyroid hormone secretion during fetal development and early in infancy results in infantile cretinism (congenital hypothyroidism). Untreated hypothyroidism is characterized in infants by respiratory difficulties, persistent jaundice, and hoarse crying and in older children by stunted growth (dwarfism), bone and muscle dystrophy, and mental deficiency.
Cretinism is three times more common in girls than in boys. Early diagnosis and treatment allow the best prognosis; infants treated before age 3 months usually grow and develop normally. Athyroid children who remain untreated beyond age 3 months and children with acquired hypothyroidism who remain untreated beyond age 2 years suffer irreversible mental retardation; their skeletal abnormalities are reversible with treatment.
In infants, cretinism usually results from defective embryonic development that causes congenital absence or underdevelopment of the thyroid gland. The next most common cause can be traced to an inherited enzymatic defect in the synthesis of thyroxine (T4) caused by an autosomal recessive gene. Less frequently, antithyroid drugs taken during pregnancy produce cretinism in infants. In children older than age 2, cretinism usually results from chronic autoimmune thyroiditis.
Signs and symptoms
The weight and length of an infant with infantile cretinism appear normal at birth, but characteristic signs of hypothyroidism develop by the time he’s 3 to 6 months old. In a breast-fed infant, onset of most symptoms may be delayed until weaning because breast milk contains small amounts of thyroid hormone.