Congenital hypothyroidism

Congenital hypothyroidism (CH) is a thyroid hormone deficiency present at birth. If untreated soon after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability. Untreated congenital hypothyroidism is also referred to as cretinism. Infants born with congenital hypothyroidism may be asymptomatic, or may display mild symptoms that go unrecognized as a problem. Significant deficiency may cause excessive sleeping, reduced interest in nursing, poor muscle tone, low or hoarse cry, infrequent bowel movements, significant jaundice, and low body temperature.

Causes of congenital hypothyroidism include iodine deficiency, developmental defect in the thyroid gland or the hypothalamus/pituitary either due to a genetic defect or an unknown cause, or dysfunction of the thyroid gland or the thyroid hormone. The source of the CH can occur at the level of the hypothalamus/pituitary gland (central CH) or the thyroid gland (primary CH). In both cases, the initial newborn screening will reflect low free thyroid hormone (fT4) levels, with elevated thyroid stimulating hormone (TSH) in primary CH and low/normal TSH in central CH.

Treatment consists of a daily dose of thyroid hormone (thyroxine) by mouth. Because the treatment is simple, effective, and inexpensive, most high-income countries utilize newborn screening with blood thyroid stimulating hormone (TSH) levels to detect congenital hypothyroidism. Most children with congenital hypothyroidism who are appropriately treated with thyroxine grow and develop normally in all respects. Approximately 1 in 4000 newborns have a severe deficiency of thyroid function; a greater number have a mild or moderate deficiency. Incidence of primary CH is 1 in every 2000 to 3000 births, while the incidence of central CH is much lower occurring in 1 of every 16,000 to 30,000 births.