Neonatal hypothyroidism, also called congenital hypothyroidism, is a disease in which there is a decreased production of thyroid hormones and in extreme cases, no production at all. It occurs in approximately one in every 3,500 to 5,000 births and is more common in Hispanics than in whites. There are several causes of neonatal hypothyroidism, most commonly an abnormally developed or missing thyroid gland. Although there are usually no symptoms with a mild decrease in thyroid hormones, infants with severe hypothyroidism have a distinctive appearance and experience multiple symptoms as the disease progresses. Tests can be performed to diagnose hypothyroidism, and if treatment starts within the first few weeks of life, it can reverse most of the negative effects of the disease.
Thyroid hormones, such as thyroxine, are necessary for normal metabolism, growth, and brain development in babies. When one has hypothyroidism, the thyroid does not produce sufficient levels of thyroid hormones. Girls are twice as likely as boys to have the disease, and it is also more frequent in twins than in single births. Although there is a higher instance of the disease in Hispanics than in whites, it is lower in black infants.
The most common causes of neonatal hypothyroidism are either a thyroid gland that has developed abnormally or one that is missing altogether. The thyroid hormones themselves could also be defective or abnormally formed. Another possible cause is a pituitary gland that is not stimulating the thyroid to produce enough thyroxine. In some cases, an iodine deficiency can lead to hypothyroidism as well.
There are several symptoms when infants have severe neonatal hypothyroidism, particularly a distinctive appearance. They can have a puffy face, coarse facial features, and a dull look. Usually they will have a protruding, enlarged tongue. The disease can also cause infants to have dry, brittle hair, a low hairline, and mottled skin.
As the disease progresses, more symptoms appear. Infants with neonatal hypothyroidism might have prolonged jaundice, be very sleepy and sluggish, and have trouble feeding. Also, since reduced thyroid hormone levels affect growth, infants with the disease generally have poor growth, short statures, and decreased muscle tone. Additional symptoms include a hoarse cry, constipation, and episodes of choking.
Most countries throughout the world will screen newborns for neonatal hypothyroidism by testing a drop of blood. The blood test checks the thyroid hormone levels to see if they are within the normal range. In some cases, a thyroid scan or x-ray of the long bones will be done to diagnose the disease.
As long as the disease is diagnosed within the first few weeks of life, the effects of neonatal hypothyroidism can be treated and reversed. Doctors will typically prescribe medication that replaces the thyroid hormone. It is generally recommended that infants with the disease have blood tests done regularly to recheck the thyroid and make sure the thyroid hormone levels remain in the normal range.
If left untreated, hypothyroidism can lead to severe mental and growth retardation, known as cretinism. The disease affects the development of the central nervous system and can cause irreversible damage. In addition, infants with the disease are at higher risk for developing heart problems.