Congenital hypothyroidism is a rare endocrine disorder affecting approximately one in 4,000 infants. The thyroid is a small butterfly shaped gland positioned at the base of the neck that produces hormones to regulate the body’s physical and mental growth. Congenital hypothyroidism occurs when an infant’s thyroid gland does not produce adequate amounts of the thyroid hormone.
Causes of Congenital Hypothyroidism
Most cases of congenital hypothyroidism occur sporadically, resulting from an error in the development of the thyroid gland. In these instances, the thyroid may have failed to develop, may have developed in the wrong location, or may have only partially formed. The error in development results in impairing the function of the thyroid stimulating hormone (TSH).
Some cases of congenital hypothyroidism are attributed to inheriting autosomal recessive traits. These cases of inborn errors can affect thyroid metabolism in normally developed thyroid glands.
Iodine deficiency was once a leading contributor to congenital hypothyroidism. With the widespread introduction of iodine into diets, the number of cases in developed countries attributed to iodine deficiency has been significantly reduced.
Symptoms of Congenital Hypothyroidism
Babies with congenital hypothyroidism may have the following symptoms:
- excessive sleeping;
- poor eating and weight gain;
- poor muscle tone;
- weak cry;
- constipation or irregular bowl movements;
- exaggerated jaundice;
- low body temperature;
- decreased activity; and/or
- dry skin or brittle hair.
Symptoms are often asymptomatic and can go unnoticed for a period of time. Because of this, it is imperative that the disorder is identified through a newborn screening test.
Diagnosing Congenital Hypothyroidism
A newborn screening test is performed on infants within 24 to 72 hours after birth. This test screens for a number of disorders, including congenital hypothyroidism. Congenital hypothyroidism is detected by increased levels of TSH or decreased levels of thyroxine (T4) in the newborn’s blood.
A pediatric endocrinologist will confirm the results of abnormal screens with an additional blood test. The doctor may also administer an ultrasound to determine the location and state of development of the thyroid gland.
Congenital Hypothyroidism: Treatment and Outcome
Once the diagnosis of congenital hypothyroidism has been confirmed, lifelong treatment with thyroid hormone replacement therapy must begin immediately. The thyroid hormone replacement therapy, levothyroxine, is a synthetic version of the thyroid hormone and is available in the form of a pill. The pill is most effectively administered by placing it on the back of the infant’s tongue and offering the breast, bottle, or pacifier to initiate swallowing. Liquid preparations of the therapy should be avoided because of potential inconsistencies with its administration.
Newborns will require monitoring of the thyroid hormones through regular blood tests. The dosage of the thyroid hormone replacement therapy is adjusted as necessary as the baby grows. The blood tests should typically be performed every two to three months until the age of three years, and more often after each change in dosage. A pediatric endocrinologist will monitor the blood test schedule and treatment.
The thyroid is fundamental in babies’ physical and mental development. If left untreated, congenital hypothyroidism can cause mental retardation and stunted physical growth. If treatment is delayed, irreversible neurological problems can occur.
Fortunately, infants who are diagnosed early and begin treatment immediately can develop normally, both physically and mentally.
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