Resistance To Thyrotropin-Releasing Hormone Syndrome

Resistance to thyrotropin-releasing hormone (TRH) syndrome is a type of central congenital hypothyroidism (see this term) characterized by low levels of thyroid hormones due to insufficient release of thyroid-stimulating hormone (TSH) caused by pituitary resistance to TRH. It may or may not be observed from birth.

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. Goiter is always absent. Slow linear growth and developmental delay are usually apparent by 4-6 months of age.

Etiology

Resistance to TRH is caused by mutations in the TRH receptor gene (TRHR; 8q23).