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Congenital hypothyroidism

What is congenital hypothyroidism?

Congenital hypothyroidism is a condition that affects infants from birth (congenital) and results from a partial or complete loss of thyroid function (hypothyroidism). The thyroid gland is a butterfly-shaped tissue in the lower neck. It makes iodine-containing hormones that play an important role in regulating growth, brain development, and the rate of chemical reactions in the body (metabolism).

Congenital hypothyroidism occurs when the thyroid gland fails to develop or function properly. In 80 to 85 percent of cases, the thyroid gland is absent, abnormally located, or severely reduced in size (hypoplastic). In the remaining cases, a normal-sized or enlarged thyroid gland is present, but production of thyroid hormones is decreased or absent. If untreated, congenital hypothyroidism can lead to mental retardation and abnormal growth. In the United States and many other countries, all newborns are tested for congenital hypothyroidism. If treatment begins in the first month after birth, infants usually develop normally.

How common is congenital hypothyroidism?

Studies of populations from North America, Europe, Japan, and Australia, indicate that congenital hypothyroidism affects 1 in 3,000 to 4,000 newborns. For reasons that remain unclear, congenital hypothyroidism affects more than twice as many females as males.

What genes are related to congenital hypothyroidism?

Mutations in the DUOX2, PAX8, SLC5A5, TG, TPO, TSHB, and TSHR genes cause congenital hypothyroidism.

Gene mutations cause the loss of thyroid function in one of two ways. Mutations in the PAX8 gene and some mutations in the TSHR gene prevent or disrupt the normal development of the thyroid gland before birth. Mutations in the DUOX2, SLC5A5, TG, TPO, and TSHB genes prevent or reduce the production of thyroid hormones, even though the thyroid gland is present.

Mutations in other genes that have not been well characterized may also cause congenital hypothyroidism.

How do people inherit congenital hypothyroidism?

Most cases of congenital hypothyroidism are sporadic, which means they occur in people with no history of the disorder in their family.

An estimated 15 to 20 percent of cases are inherited. Many inherited cases are autosomal recessive, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.

Some inherited cases (those with a mutation in the PAX8 gene or certain TSHR mutations) have an autosomal dominant pattern of inheritance, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

Congenital Hypothyroidism on Wikipedia

'''Congenital hypothyroidism''' is a condition of thyroid hormone deficiency present at birth. Approximately 1 in 4000 newborn infants has a severe deficiency of thyroid function, while even more have mild or partial degrees. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent mental retardation. Treatment consists of a daily dose of thyroid hormone (thyroxine) by mouth. Because the treatment is simple, effective, and inexpensive, nearly all of the developed world practices newborn screening to detect and treat congenital hypothyroidism in the first weeks of life.

Causes

Around the world, the most common cause of congenital hypothyroidism is iodine deficiency, but in most of the developed world and areas of adequate environmental iodine, cases are due to a mixture of known and unknown causes. Most commonly there is a defect of development of the thyroid gland itself, resulting in an absent (athyreosis) or underdeveloped (hypoplastic) gland. A hypoplastic gland may develop higher in the neck or even in the back of the tongue. A gland in the wrong place is referred to as ''ectopic'', and an ectopic gland at the base or back of the tongue is a ''lingual'' thyroid. Some of these cases of developmentally abnormal glands result from genetic disease, and some are "sporadic," with no identifiable cause. Congenital hypothyroidism can also occur due to genetic defects of thyroxine or triiodothyronine synthesis within a structurally normal gland. Among specific defects are thyrotropin (TSH) resistance, iodine trapping defect, organification defect, thyroglobulin, and iodotyrosine deiodinase deficiency. In a small proportion of cases of congenital hypothyroidism, the defect is due to a deficiency of thyroid stimulating hormone, either isolated or as part of congenital hypopituitarism. In some instances, hypothyroidism detected by screening may ...   [ Read More ]


External Resources

Thyroid Disorders - Primary, secondary, juvenile and congenital hypothyroidism by David W. Gardner M.D. Includes photos of patients.

Congenital Hypothyroidism - Information about this hereditary condition that is fairly uncommon. Learn the importance of newborn screening tests to prevent mental retardation.

Thyroid Disease in Childhood - Learn about the types of thyroid disorders affecting children, growth, metabolism, congenital hypothyroidism and congenital goitre.

Thyroid Disorders & Treatments - Congenital Hypothyroidism - Discusses the cause, screening process, incidence and types, Low T4, and outcome.

Congenital Hypothyroidism - A case report of a child with severe disease symptoms that include protruding tongue, pericardial effusion, dry thick skin, sepsis, and lethargy. From Pediatric Oncall.

Thyroid Disorders in Children - A mother's personal story about her pregnancy and a daughter with Congenital Hypothyroidism.

Children With Congenital Hypothyroidism and Their Siblings: Do They Really Differ? - Study suggests that even with treatment early in life, due to newborn screening, may have reduced IQ relative to siblings.

Congenital Hypothyroidism - Covers the causes, prevention, symptoms, tests, complications, diagnosis, and treatment. From AllRefer Health.

Congenital Hypothyroidism and Nonimmune Hydrops Fetalis: Associated? - Presents a case where there is an abnormal accumulation of fluid in the fetal compartments, including ascites, pleural effusion, pericardial effusion, and skin edema.


Related Pages on HealthTales.com:

Congenital Heart Defects
Congenital bilateral absence of the vas deferens

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