Congenital hypothyroidism occurs when a baby is born with a thyroid gland that is not producing enough thyroid hormones. Untreated congenital hypothyroidism is the most common cause of mental retardation.
If the results of thyroid testing (T4 and TSH) indicate congenital hypothyroidism, the health care professional may prescribe thyroid supplements.
Limitations of congenital hypothyroidism screening:
The thyroid test measures the amount of a hormone that is present in the baby’s blood at the time the test is performed. At birth, however, there are thyroid hormones from the mother present in the newborn’s circulation that can mask the baby’s low thyroid hormone level. Discharging a baby shortly after delivery does not allow enough time for the mother’s thyroid substance to disappear from the baby’s circulation. To more accurately diagnose congenital hypothyroidism, the recommended timing is as follows:
1. The specimen should be collected between 2 and 6 days of age (optimally between 48 hours and 4 days).
2. If the baby is discharged prior to 48 hours of age, thyroid testing should be performed as close to the time of discharge as possible, but no later than 7 days of age.
3. If the baby’s blood was collected before 24 hours of age, a second specimen should be tested before 2 weeks of age.
Source
S1
American Academy of Pediatrics. Update of newborn screening and therapy for congenital hypothyroidism. Jun 2006. Pediatrics 117(6):220-303.
