Thyroid dysgenesis

Other Names: Thyroid, ectopic; Thyroid hypoplasia; Thyroid agenesis

Thyroid hypoplasia is a form of thyroid dysgenesis characterized by incomplete development of the thyroid gland that results in primary congenital hypothyroidism, a permanent thyroid deficiency that is present from birth.

Epidemiology

Prevalence is estimated at around 1/28,000. Thyroid hypoplasia and athyreosis combined account for one-third of cases of thyroid dysgenesis.

Cause

Familial cases of thyroid hypoplasia are caused by mutations in the FOXE1, NKX2-1, NKX2-5 or PAX8 genes (9q22, 14q13, 5q34 and 2q12-q14). Mutations that result in partial inactivation of the TSHR gene (14q31) can present with thyroid hypoplasia.

Inheritance

Thyroid hypoplasia is generally thought to be sporadic. However, recent evidence points to the possibility of a genetic component. Around 2% of cases have been shown to be familial.

Signs and symptoms

Clinical manifestations of thyroid hypoplasia are often subtle or not present at birth, probably as a result of trans-placental passage of some maternal thyroid hormone or due to the fact that many infants have some thyroid production of their own. More specific symptoms and signs do not develop until several months of age. Common clinical features and signs include decreased activity and increased sleep, feeding difficulty and constipation, prolonged jaundice, myxedematous facies, large fontanels (especially posterior), macroglossia, a distended abdomen with umbilical hernia, and hypotonia. Goiter is always absent. Slow linear growth and developmental delay are usually apparent by 4-6 months of age. Without treatment thyroid hypoplasia results in severe intellectual deficit and short stature.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Abdominal distention(Abdominal bloating)
• Coarse facial features(Coarse facial appearance)
• Constipation
• Fatigue(Tired)
• Hypothyroidism(Underactive thyroid)
• Jaundice(Yellow skin)
• Large fontanelles(Wide fontanelles)
• Macroglossia(Abnormally large tongue)
• Muscular hypotonia(Low or weak muscle tone)
• Thyroid hypoplasia(Small thyroid gland)

30%-79% of people have these symptoms

• Global developmental delay
• Intellectual disability, severe(Early and severe mental retardation)
• Short stature(Decreased body height)

Diagnosis

Imaging studies are required to confirm the diagnosis.

NIH genetic and rare disease info

• NIH info on Thyroid dysgenesis

Thyroid dysgenesis is a rare disease.

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