(Cretinism)
Definition
Congenital hypothyroidism is a condition where a newborn has decreased or absent thyroid function and thyroid hormone production.
The thyroid is a gland in the lower neck that makes iodine-containing hormones that regulate growth, brain development, and metabolism. Hypothyroidism occurs when the gland is absent, abnormally developed, destroyed, or reduced in size, or the production of thyroid hormones is decreased or absent.
The Thyroid Gland
The longer this disorder is unrecognized and untreated, the more damage is done to the brain and the greater the risk of mental retardation and abnormal growth. Fortunately, with early recognition and treatment, damage can be avoided.
Causes and Risks
In most cases, the cause of congenital hypothyroidism is unknown. A small percentage of cases are inherited and caused by mutations in the genes producing the enzymes (proteins) required to make thyroid hormones. Here are other causes:
• Medication during pregnancy, such as radioactive iodine therapy
• Maternal autoimmune disease
• Too much iodine during pregnancy
• Anatomic defect in thyroid gland
• Inborn error of metabolism
Symptoms
If your newborn experiences any of these symptoms, do not assume it is due to congenital hypothyroidism. These symptoms may be caused by other, less serious health conditions. However, if you notice any one of them, see the baby’s pediatrician.
• Puffy face
• Coarse facial features
• Dull look
• Thick protruding tongue
• Poor feeding
• Choking episodes
• Constipation or reduced stooling
• Jaundice
• Short stature
• Swollen, protuberant belly button
• Decreased activity
• Sleeps a lot
• Rarely cries or hoarse cry
• Dry brittle hair; low hairline
• Poor muscle tone
• Cool and pale skin
• Goiter (enlarged thyroid)
• Birth defects (eg, heart valve abnormality)
• Poor weight gain
• Poor growth
Diagnosis
At birth, most infants are screened for congenital hypothyroidism. A pediatric endocrinologist is appropriate if a specialist is needed. Tests may include the following:
• Measurement of free (unbound) thyroxine (T4) levels in the blood
• Measurement of thyroid stimulating hormone (TSH) in the blood
• Thyroid scan (technetium)
Treatment
If untreated, congenital hypothyroidism can lead to severe mental retardation and growth retardation. However, if caught early at birth (preferably during the first two weeks of life) when the brain and nervous system are not yet fully developed, thyroid hormone replacement could prevent damage.
Congenital hypothyroidism is generally treated with hormone replacement therapy. The hormone thyroxine is given in one of the following forms:
• Levothyroxine
• Levothyroid
• Levoxyl
• Synthroid
Typically, the tablets should be given at least thirty minutes before a meal or feeding. Treatment is individualized in that the amount that is absorbed and handled by the body differs among individuals. Once medication starts, the blood levels of TSH and T4 are frequently monitored to keep the values within normal range. If values are kept within a normal range, there are no side effects or complications.
Prevention
Most cases of congenital hypothyroidism are not preventable. The following are some things the mother can do during pregnancy to reduce the risk.
• Mother shouldn’t have radioactive iodine treatment or use iodine as antiseptic.
• Mother should consume enough, but not too much iodine.
