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Congenital Hypothyroidism

(Cretinism)

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.
The Thyroid Gland
IMAGE
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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, but it is probably genetic. The most common known causes are abnormal development of the thyroid gland or a defect in producing thyroid hormone. About 15% of cases are inherited.
Babies may have a temporary shortage in their thyroid hormones, which is more common if born before 40 weeks.

Risk Factors

Factors that may increase the chance of congenital hypothyroidism include:

Symptoms

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

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:

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 hormone.
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:

RESOURCES

American Thyroid Association http://www.thyroid.org

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

CANADIAN RESOURCES

Health Canada http://www.hc-sc.gc.ca

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

References

American Academy of Pediatrics, Rose SR, Section on Endocrinology and Committee on Genetics, et al. Update of newborn screening and therapy for congenital hypothyroidism. Pediatrics. 2006;117(6):2290-2303.

Bongers-Schokking JJ, Koot HM, et al. Influence of timing and dose of thyroid hormone replacement on the development in infants with congenital hypothyroidism. J Ped. 2000;136(3):292-297.

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

Gruters A, Krude H, Biebermann H. Molecular genetic defects in congenital hypothyroidism. Europ J Endocr. 2004;151 Suppl 3:U39-U44.

Congenital hypothyroidism. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated March 24, 2016. Accessed March 29, 2016.

LeFranchi SH, Austin J. How should we be treating children with congenital hypothyroidism. J Pediatr Endocrinol Metab. 2007;20(5):559-578.

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