Congenital Hypothyroidism is inadequate thyroid hormone production in newborn infants. This can occur because of an anatomic defect in the gland, an inborn error of thyroid metabolism, or iodine deficiency.
The term endemic cretinism is used to describe clusters of infants with goiter and hypothyroidism in a defined geographic area.
The term sporadic cretinism was initially used to describe the random occurrence of cretinism in nonendemic areas. The cause of these abnormalities was identified as nonfunctioning or absent thyroid glands.
History
• In regions of iodide deficiency and a known prevalence of endemic cretinism, the diagnosis may be straightforward.
• Infants with congenital hypothyroidism are usually born at term or after term.
• Symptoms and signs include the following:
o Decreased activity
o Large anterior fontanelle
o Poor feeding and weight gain
o Small stature or poor growth
o Jaundice
o Decreased stooling or constipation
o Hypotonia
o Hoarse cry
• They are described as "good babies" because they rarely cry and sleep most of the time.
• Family history: similarly affected infants or family members with unexplained mental retardation.
• Maternal history of a thyroid disorder and mode of treatment, whether before or during pregnancy, can occasionally provide the etiology of the infant’s problem.
• Congenital hypothyroidism is more common in infants with birthweights less than 2,000 g or more than 4,500 g.
Physical
The physical findings of hypothyroidism may or may not be present at birth.
- Signs include the following:
• Coarse facial features
• Macroglossia
• Large fontanelles
• Umbilical hernia
• Mottled, cool, and dry skin
• Developmental delay
• Pallor
• Myxedema
• Goiter
- Other birth defects: mainly atrial and ventricular septal defects.
- Anemia may occur, due to decreased oxygen carrying requirement.
Causes
- Endemic cretinism: iodine deficiency, naturally occurring goitrogens.
- Congenital hypothyroidism:
• Dysgenesis of the thyroid gland
• Inborn errors of thyroid hormone metabolism – Dyshormonogenesis
• Thyroid hormone resistance (ie, thyroid hormone receptor abnormalities)
• Maternal autoimmune disease (transient or permanent)
• Iatrogenic causes - Maternal use of thioamides, iodine excess, radioactive iodine therapy
• TSH or thyrotropin-releasing hormone (TRH) deficiencies
Medical Care
The mainstay in the treatment of congenital hypothyroidism is early diagnosis and thyroid hormone replacement. One study suggested that optimal care includes diagnosis before age 13 days and normalization of thyroid hormone blood levels by age 3 weeks.
Endemic cretinism can be prevented by appropriate iodine supplementation. Iodization of salt is the usual method, but cooking oil, flour, and drinking water have also been iodinated for this purpose. Long-acting intramuscular injections of iodized oil (Lipiodol) have been used in some areas.
Diet
Dietary iodide supplementation, especially in endemic areas, can prevent endemic cretinism. Dietary iodine deficiency is the most common preventable cause of brain damage worldwide.
Soy-based formulas may decrease the absorption of levothyroxine. This is not a contraindication to their use, even in infants with congenital hypothyroidism. Switching an infant from a milk-based formula to a soy-based formula may increase the dose of thyroid hormone needed to maintain a euthyroid status.
Medication
Only levothyroxine is recommended for treatment. It has been established as safe, effective, inexpensive, easily administered, and easily monitored.
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