Hypothyroidism in babies results from either a small, absent or poorly functioning thyroid gland. The thyroid gland is located in the throat. Hypothyroidism in babies is referred to as congenital because the baby is born with the disorder, rather than developing it later in life. An old term for this disorder used to be cretinism.
The thyroid gland is responsible for the overall control of the body's metabolism. If it is not functioning properly, then brain development can be slow (possibly leading to mental handicap) and physical development can be delayed (such as dwarfism) if the baby is not treated early.
The signs of congenital hypothyroidism (or CH) may not be obvious at birth. However babies with CH can sometimes have severe prolonged jaundice, a large tongue, a hoarse cry, be lethargic and sleep for prolonged periods and occasionally have a hernia near their belly button (although these hernias can also occur in healthy babies). Damage to the brain can be permanent if babies with CH are not treated early. They are also at increased risk of hearing impairment. It is for this reason babies with CH should have their hearing checked when older.
Congenital Hypothyroidism affects about 1 in 3,500 babies (or 0.00033%). The newborn screening test for this disorder has been available since about 1977 and is aimed at detecting hypothyroidism early, so that the baby can be started on a medication called thyroxine, to prevent or minimise, mental and physical delay.
It is possible for the newborn screening test to give a false positive result (meaning the baby is thought to have CH but actually does not). This is possible for less than 1% of babies detected. It is also possible to have a false negative result (meaning that the baby does have CH but the test did not detect it). This can happen for up to 5% of babies with congenital hypothyroidism.
The baby will require further blood tests before treatment is commenced.