Master's in Genetic Counseling (MGC)

Congenital Hypothyroidism

Congenital hypothyroidism is a condition in which there is inadequate production of functional thyroid hormone. The most common etiologies of congenital hypothyroidism are total or partial failure of the thyroid gland to develop, or its development in an abnormal location.

Clinical Features

Infants with congenital hypothyroidism may appear normal for the first several months of life. Clinical signs may consist of jaundice, constipation, poor muscle tone, lethargy, feeding problems, a puffy face, large tongue, umbilical hernia, and hypothermia. If untreated, affected individuals may suffer profound mental retardation, growth delay, deafness, and neurologic abnormalities.

Laboratory Tests

Screening for congenital hypothyroidism is performed by determining the level of T4 (thyroxine) and TSH (thyroid stimulation hormone) in the dried filter paper blood spot. Normal, borderline, and abnormal results are reported based upon the combined values of both assays, with the methods of interpretation varying from state to state.

Treatment

For affected individuals, synthetic thyroid hormone is administered daily. Periodic thyroid function tests and re-evaluation of growth and development are necessary. If the serum T4 level is maintained within the normal range, normal growth and development can be achieved. Pediatric endocrinology consultation is beneficial for diagnostic and follow up purposes. For specific treatment guidelines, please consult with a pediatric endocrinology specialist.

Screening Practice Considerations

While nutritional factors do not influence the results of the newborn screening test for congenital hypothyroidism, a blood transfusion may alter the results. It is desirable to obtain specimens before a transfusion occurs, regardless of age.

TSH levels rise in the first few hours after birth. If a specimen is collected during the first 24 hours of life, TSH levels may be elevated. This may be a transient elevation only, and follow-up testing is still required. Specimens should be collected as late as possible before discharge (but no later than 72 hours).

Premature infants may demonstrate a physiologic reduction in T4 levels. TSH levels are usually normal. These infants require repeat testing and special follow-up measures to ensure that the low T4 levels rise into the normal range as the infant matures. This may take several weeks. If T4 levels do not rise into the normal range, referral to a pediatric endocrinologist is recommended.

10 to 15% of congenital hypothyroidism cases will have normal newborn screening results, with abnormal results evident only after the first few weeks of life. Therefore, it is critical that practitioners be aware of the clinical presentation of this disorder and arrange for appropriate testing regardless of newborn screening results.

For additional information on newborn screening for congenital hypothyroidism, please see the American Academy of Pediatrics' "Newborn screening for congenital hypothyroidism: recommended guidelines" (Pediatrics, 91:6, 1203-1209).

Click on a state below for state specific follow-up procedures.

• Delaware
• Maryland
• New Jersey
• Pennsylvania
• Virginia
• West Virginia
• Washington, D.C.