Definition

The thyroid is a gland in the lower neck. It makes hormones that regulate growth, brain development, and metabolism. Hypothyroidism is a low or absent production of these hormones. Congenital means the conditions is present since birth.

If this condition is not treated it can cause damage to the brain. This can lead to intellectual disability and abnormal growth.

Causes

In most cases, the cause is unknown. The most common known cause is abnormal development of the thyroid gland. A small percentage of cases are inherited.

Babies born before 40 weeks may have a temporary shortage in the thyroid hormones.

Risk Factors

Factors that may increase the risk of congenital hypothyroidism include:

• Medication during pregnancy, such as radioactive iodine therapy
• Maternal autoimmune disease
• Too much iodine during pregnancy
• Inborn error of metabolism

Symptoms

Symptoms or signs take time to develop. The symptoms of congenital hypothyroidism may include the following:

• Puffy face
• Coarse facial features
• Dull look
• Thick protruding tongue
• Poor feeding
• Choking episodes
• Constipation or reduced stooling
• Yellow skin color— jaundice
• Short stature
• Swollen abdomen
• Decreased activity
• Sleeps a lot
• Rarely cries or hoarse cry
• Dry brittle hair; low hairline
• Poor muscle tone
• Cool and pale skin
• Poor weight gain due to poor appetite
• Poor growth
• Difficult breathing
• Low temperature
• Swollen hands, feet and genitals

Diagnosis

At birth, most infants are screened for this condition. Blood tests will be able to identify thyroid levels. Images of the thyroid may also be taken with:

• Thyroid scan (technetium)
• Nuclear imaging (scintigraphy)

Treatment

The outcome is best if the condition is caught early. It is important to start treatment before the brain and nervous system are fully developed. If treatment is given early, it could prevent damage. Left untreated, the condition can lead to poor mental development and delayed growth.

Medication will treat the hypothyroidism. The medication will replace the missing hormones.

Once medication starts, the levels of thyroid hormones are checked often. This will help to keep the values within normal range. If values are kept within a normal range, there are no side effects or complications.

Prevention

Most cases cannot be prevented. The following are some things the mother can do during pregnancy to reduce the risk:

• Avoid radioactive iodine treatment or iodine as antiseptic during pregnancy
• Consume enough, but not too much iodine during pregnancy

Genetics Home Reference http://ghr.nlm.nih.gov

Thyroid Foundation of Canada http://www.thyroid.ca

Castanet M, Polak M, et al. Familial forms of thyroid dysgenesis. Endocr Dev. 2007;10:15-28.

Congenital hypothyroidism. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed
Updated November 3, 2014. Accessed December 11, 2014.

Gruters A, Krude H, Biebermann H. Molecular genetic defects in congenital hypothyroidism. Europ J Endocr. 2004;151:39-44.

LeFranchi SH, Austin J. How should we be treating children with congenital hypothyroidism. J Pediatr Endocrinol Metab. 2007;20:559-578.

Update of newborn screening and therapy for congenital hypothyroidism. American Academy of Pediatrics. Pediatrics. 2006;117:2290-2303.