Congenital Hypothyroidism
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Congenital Hypothyroidism

(Cretinism)

En Español (Spanish Version)

Definition

Congenital hypothyroidism is a condition where a newborn has decreased or absent thyroid function and thyroid hormone production.

The thyroid is a gland in the lower neck that makes iodine-containing hormones that regulate growth, brain development, and metabolism. Hypothyroidism occurs when the gland is absent, abnormally developed, destroyed, or reduced in size, or the production of thyroid hormones is decreased or absent.

The Thyroid Gland

© 2008 Nucleus Medical Art, Inc.

The longer this disorder is unrecognized and untreated, the more damage is done to the brain and the greater the risk of mental retardation and abnormal growth. Fortunately, with early recognition and treatment, damage can be avoided.

Causes and Risks

In most cases, the cause of congenital hypothyroidism is unknown. A small percentage of cases are inherited and caused by mutations in the genes producing the enzymes (proteins) required to make thyroid hormones. Here are other causes:

  • Medication during pregnancy, such as radioactive iodine therapy
  • Maternal autoimmune disease
  • Too much iodine during pregnancy
  • Anatomic defect in thyroid gland
  • Inborn error of metabolism

Symptoms

Most doctors now depend on the screening test in newborns to diagnose this condition since the 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
  • Jaundice prolonged
  • Short stature
  • Swollen, protuberant belly button
  • Decreased activity
  • Sleeps a lot
  • Rarely cries or hoarse cry
  • Dry brittle hair; low hairline
  • Poor muscle tone
  • Cool and pale skin
  • Goiter (enlarged thyroid)
  • Birth defects (eg, heart valve abnormality)
  • Poor weight gain due to poor appetite
  • Poor growth
  • Difficult breathing
  • Slow pulse
  • Low temperature
  • Swollen hands, feet and genitals

Diagnosis

At birth, most infants are screened for congenital hypothyroidism. A pediatric endocrinologist is appropriate if a specialist is needed. Tests may include the following:

  • Measurement of free (unbound) thyroxine (T4) levels in the blood
  • Measurement of thyroid stimulating hormone (TSH) in the blood
  • Thyroid scan (technetium)

Treatment

If untreated, congenital hypothyroidism can lead to severe mental retardation and growth retardation. However, if caught early at birth (preferably during the first two weeks of life) when the brain and nervous system are not yet fully developed, thyroid hormone replacement could prevent damage.

Congenital hypothyroidism is generally treated with hormone replacement therapy. The hormone thyroxine is given in one of the following forms:

  • Levothyroxine
  • Levothroid
  • Levoxyl
  • Synthroid

Typically, the tablets should be given at least thirty minutes before a meal or feeding. Treatment is individualized in that the amount that is absorbed and handled by the body differs among individuals. Once medication starts, the blood levels of TSH and T4 are frequently monitored 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 of congenital hypothyroidism are not preventable. The following are some things the mother can do during pregnancy to reduce the risk.

  • Mothers should not have radioactive iodine treatment or use iodine as antiseptic.
  • Mothers should consume enough, but not too much iodine.

RESOURCES

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

Med Help International
http://www.medhelp.org

CANADIAN RESOURCES

Canadian Task Force on Preventive Health
http://www.ctfphc.org

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

References

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

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

Congenital hypothyroidism. National Institute of Health website. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/001193.htm . Accessed September 12, 2005.

Congenital hypothyroidism. Thyroid Foundation of America website. Available at: http://www.tsh.org/disorders/pregnancy/newborns.html . Accessed September 12, 2005.

Congenital hypothyroidism. US National Library of Medicine website. Available at: http://ghr.nlm.hig.gov/condition=congenitalhypothyroidism . Accessed September 12, 2005.

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;20:559-78.

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



Last reviewed January 2008 by David Juan, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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