Congenital hypothyroidism

Congenital hypothyroidism (CH) is thyroid hormone deficiency present at birth. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability. Infants born with congenital hypothyroidism may show no effects, or may display mild effects that often 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 and a developmental defect in the thyroid gland, either due to a genetic defect or of unknown cause. Treatment consists of a daily dose of thyroid hormone (thyroxine) by mouth. Because the treatment is simple, effective, and inexpensive, most of the developed world utilizes newborn screening with blood thyroid stimulating hormone (TSH) levels to detect congenital hypothyroidism. Most children with congenital hypothyroidism correctly 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. Infants born with congenital hypothyroidism may show no effects, or may display mild effects that often go unrecognized as a problem: excessive sleeping, reduced interest in nursing, poor muscle tone, low or hoarse cry, infrequent bowel movements, significant jaundice, and low body temperature. If the fetal thyroid hormone deficiency is severe because of complete absence (athyreosis) of the gland, physical features may include a larger anterior fontanel, persistence of a posterior fontanel, an umbilical hernia, and a large tongue (macroglossia). In the era before newborn screening, less than half of cases of severe hypothyroidism were recognized in the first month of life. As the months proceeded, these babies would grow poorly and be delayed in their development.