Causes
The most common cause of congenital hypothyroidism is an ectopic thyroid. Just like an ectopic pregnancy — in which the fertilized egg starts to grow outside the uterus — an ectopic thyroid grows in an inappropriate location. Because the ectopic thyroid is not properly located, these glands generally don't function correctly and fail to produce enough thyroid hormone.
Development of the thyroid gland begins in the first trimester of pregnancy, when the first remnants of thyroid tissue in the back of the tongue start making the gradual descent to the base of the neck. There, a healthy gland grows and forms, then starts churning out thyroid hormone that aids in the development of the fetus. But if that tissue doesn't migrate properly, the thyroid gland is said to be ectopic.
In most cases of ectopic thyroid, the thyroid gland develops where it originates, in the back of the tongue. This type of development is called a lingual thyroid. On occasion, these misplaced thyroid glands actually do produce enough thyroid hormone, and the patient may not even know that anything is wrong.
Lingual thyroid is more common in girls than boys. Though most are small and less than a centimeter, some can grow to four centimeters. In some patients, a lingual thyroid can interfere with swallowing or breathing.
The majority of babies born with a lingual thyroid go on to develop hypothyroidism. Treatment to prevent hypothyroidism usually involves suppressing TSH levels so that the lingual thyroid does not grow. If it gets too big or affects swallowing, your child may require surgery. People with lingual thyroid usually undergo regular monitoring of thyroid hormone levels.
Essential
Lingual thyroid isn't detected only in children. In rare cases, they may not become apparent until adulthood, even into your seventies. Signs and symptoms are generally the same — shortness of breath and difficulty swallowing.
Some babies with congenital hypothyroidism are born without a thyroid gland or one that is smaller than normal. In some cases, a baby has hypothyroidism because the mother had a deficiency of iodine, a situation that is rare in the United States. Some babies may lack an enzyme required for iodine metabolism, which causes a deficit in thyroid hormone production. Babies born without this enzyme may also be deaf.
Signs and Symptoms
Most babies born with hypothyroidism look perfectly normal at birth. That's why the screening process is essential for detecting babies who lack adequate thyroid hormone. But some babies may actually have one or more symptoms, including:
Decreased birth weight
Puffy face
Swollen tongue
A hoarse cry
Cold hands and feet
Persistent constipation and a bloated abdomen
Prolonged jaundice
Lack of energy and constant fatigue
Poor muscle tone
Little or no growth over time
Although the newborn screening has become routine, parents should still be on the lookout for suspicious symptoms. And if you come from a family where thyroid disease is prevalent, it doesn't hurt to ask about the screening to make sure it's done.
Cretinism
Children without enough thyroid hormone are at serious risk for cretinism, a condition that causes severe retardation in both physical and mental development. Cretinism is common in regions of the world where iodine is deficient, goiter is endemic, and screening is not performed. Worldwide, cretinism is the most common cause of mental retardation.
Fact
According to MedicineNet.com, the word cretin may have come from the Old French term chretien, meaning “Christian.” Fleeing persecution, Christians moved into the Pyrenees valleys, where a lack of iodine caused them to have children with congenital hypothyroidism. Another theory is that the word could have come from cretura, meaning “creature,” or creta, meaning “chalk” or “pale.”
People who have cretinism suffer numerous problems. Growth is permanently stunted, and an adult will be well below normal height. Cretinism also causes the skin to be thick and flabby, and waxy in color. Most children with cretinism have a flattened nose and a protruding stomach. Gait and speech are notably slow, and intellectual development is seriously limited.
