Isolated Thyroid-Stimulating Hormone Deficiency

A type of central congenital hypothyroidism, a permanent thyroid deficiency that is present from birth, characterized by low levels of thyroid hormones due to a deficiency in TSH synthesis.

Epidemiology

Prevalence is unknown.

Clinical description

The clinical manifestations are often subtle, 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 often 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. Slow linear growth and developmental delay are usually apparent by 4-6 months of age.

Etiology

Isolated TSH deficiency is transmitted in an autosomal recessive manner and is caused by mutations in the TSHB subunit gene (1p13).