Screening for Congenital Hypothyroidism

NYU Langone is a New York State Department of Health–designated care center for children with congenital hypothyroidism, and our doctors are specialists in treating this rare condition. Children born with congenital hypothyroidism have a partial or complete loss of thyroid function. This means the thyroid does not produce enough of the hormones needed for growth and brain development. 

Newborn babies typically have no obvious signs of hypothyroidism. For this reason, screening is important to prevent the developmental delays and permanent intellectual disability that may result in children with hypothyroidism. Screening requires a simple blood test and is mandatory in the United States. A few drops of blood, taken by pricking a newborn baby’s heel, are placed on a special card that is sent to a New York State Department of Health laboratory. 

The laboratory measures two hormones that show how well the thyroid is working—thyroxine (T4), a hormone produced in the thyroid, and thyroid-stimulating hormone (TSH), a hormone made in the pituitary gland that signals to the thyroid that it should produce more T4 when levels are low. A baby with higher-than-normal TSH levels or lower-than-normal T4 levels may have congenital hypothyroidism. 

Screening for congenital hypothyroidism is recommended when a baby is three days old. Infants who are discharged from the hospital earlier should be tested immediately before they leave, although there is a risk of a false–positive result because of a brief rise in TSH levels before a baby is three days old. 

The laboratory alerts your pediatrician by the time your baby is nine days old if the screening test result suggests a problem with the thyroid. A positive newborn screening result does not mean that your baby has congenital hypothyroidism. Additional blood tests must be performed immediately to enable doctors to make an accurate diagnosis.

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