Congenital hypothyroid syndro... Health Article

Definition

Congenital hypothyroid syndrome is a condition in which a child is born with a deficiency in thyroid gland activity or thyroid hormone levels.

Description

The thyroid gland is a small gland in the front of the neck that secretes thyroid hormones called thyroxine (T4) and triiodothyronine (T3) into the bloodstream. Some of the T4 is converted into T3 by the liver and kidney. These thyroid hormones help regulate a great number of processes. A deficiency in the level of these hormones can affect the brain, heart, muscles, skeleton, digestive tract, kidneys, reproductive function, blood cells, other hormone systems, heat production, and energy metabolism.

In most cases of congenital hypothyroidism, the thyroid gland is either completely absent or severely under-developed. Sometimes thyroid tissue is located in ectopic, or abnormal, locations along the neck.

Other abnormalities can lead to congenital hypothyroidism including:

• • abnormal synthesis of thyroid hormones;
• • abnormal synthesis of thyroid-stimulating hormone (TSH) or thyrotropin-releasing hormone (TRH), which are regulatory hormones that affect the production of thyroid hormones;
• • abnormal response to thyroid hormones, TSH or TRH;
• • inadvertent administration of harmful drugs or substances to the pregnant mother, possibly resulting in temporary congenital hypothyroidism in the newborn;
• • dietary deficiency of iodine, a raw component vital to the manufacture thyroid hormones.

Genetic profile

Most causes of congenital hypothyroidism are not inherited. Some abnormalities in thyroid hormone synthesis (TSH synthesis), or the response to TSH, are inherited in autosomal recessive fashion. This means that both parents have one copy of the changed (mutated) gene but do not have the condition. Abnormal response to thyroid hormone may be an autosomal dominant condition, meaning that only one parent has to pass on the gene mutation in order for the child to be affected with the syndrome.

Demographics

Congenital hypothyroidism occurs in one in every 4,000 newborns in the United States. It is twice as common in girls as in boys. The condition is less common in African Americans and more common in Hispanics and Native Americans.