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Am Fam Physician. 2009;80(10):3-5

Summary of Recommendations and Evidence

The U.S. Preventive Services Task Force (USPSTF) recommends screening for congenital hypothyroidism in newborns (Table 1). A recommendation.

PopulationAll newborn infants*
RecommendationScreen all newborn infants for congenital hypothyroidism
Grade: A
Screening testsTwo methods of screening are used most often in the United States:
  • Primary TSH with backup T4

  • Primary T4 with backup TSH.

Screening for congenital hypothyroidism is mandated in all 50 states and the District of Columbia.
Physicians should become familiar with the tests used in their area and the limitations of the screening strategies employed.
Timing of screeningInfants should be tested between two and four days of age.
Infants discharged from hospitals before 48 hours of life should be tested immediately before discharge.
Specimens obtained in the first 24 to 48 hours of life may be falsely elevated for TSH regardless of the screening method used.
Suggestions for practiceInfants with abnormal screens should receive confirmatory testing and begin appropriate treatment with thyroid hormone replacement within two weeks after birth.
Children with positive confirmatory testing in whom no permanent cause of congenital hypothyroidism is found should undergo a 30-day trial of reduced or discontinued thyroid hormone therapy to determine whether the hypothyroidism is permanent or transient.
This trial of reduced or discontinued therapy should take place sometime after the child reaches three years of age.

Rationale

Importance. Primary congenital hypothyroid-ism occurs in approximately one in every 3,000 to 4,000 newborns in the United States. In the absence of prompt diagnosis and treatment, most persons with this disorder will develop various degrees of neurologic, motor, and growth deficits, including irreversible mental retardation.

Benefits of detection and early intervention.Early detection of congenital hypothyroidism by neonatal screening and appropriate treatment substantially improves neurodevelopmental outcomes for affected persons.

Harms of detection and early treatment.Positive test results, whether true positive or false positive, cause anxiety in parents. For some parents, this anxiety may be considerable.

USPSTF assessment.The USPSTF concludes that there is high certainty that the net benefit of screening for congenital hypothyroidism in newborns is substantial.

Clinical Considerations

  • Patient population.This recommendation applies to all infants born in the United States. Premature, very low–birth-weight, and ill infants may benefit from additional screening because these conditions are associated with decreased sensitivity and specificity of screening tests.

  • Screening tests. Screening for congenital hypothyroidism is mandated in all 50 states and the District of Columbia, though methods of screening vary. There are two main methods used in the United States: primary thyroid-stimulating hormone (TSH) performed on capillary blood collected from a heel stick and absorbed onto filter paper with backup thyroxine (T4), and primary T4 with backup TSH. A few states use both tests in initial screening.1,2 Physicians should become familiar with the tests used in their area and the limitations of the employed screening strategy. For example, a primary TSH method may be falsely negative in low and very low–birth-weight infants with congenital hypothyroidism because of delayed elevation in TSH. Additionally, few states currently screen for centrally mediated congenital hypothyroidism. Families should be provided with appropriate information about newborn screening tests, including the benefits and harms of screening. They should be aware of the potential of a false-positive test, and the process required for definitive testing. Nationally, only one in 25 positive screening tests is confirmed.1 Normal newborn screening results for congenital hypothyroidism should not preclude appropriate evaluation of infants presenting with clinical signs and symptoms suggestive of hypothyroidism.

  • Timing of screening. Infants should be tested between two and four days of age. Infants discharged from hospitals before 48 hours of life should be tested immediately before discharge. Specimens obtained in the first 24 to 48 hours of life may be falsely elevated for TSH regardless of the screening method used.

  • Treatment. Primary care physicians should ensure that infants with abnormal screening results receive confirmatory testing and begin appropriate treatment with thyroid hormone replacement within two weeks after birth. Children with positive confirmatory testing in whom no permanent cause of congenital hypothyroidism is found (e.g., lack of thyroid tissue on thyroid ultrasonography or thyroid scan) should undergo a 30-day trial of reduced or discontinued thyroid hormone therapy at some point after three years of age to determine if the hypothyroidism is permanent or transient.

Future Research Needs

Additional research is needed to determine the cost benefit of different screening strategies, including the use of newer, more accurate TSH measurements, combined TSH-T4 strategies, and methods designed to identify primary and central hypothyroidism. Future research should be directed at determining the incremental benefits of routine collection of a second specimen from two-week-old newborns. Additional research is also needed on how to ameliorate the effects on families of false-positive results from congenital hypothyroidism and other newborn screening tests. These may include improved communication for informing parents, better newborn screening informational materials, and reduced time to rule out congenital disorders.

Discussion

In 1996, the USPSTF reviewed the evidence on screening for congenital hypothyroidism in newborns and recommended screening.3 In 2006, the USPSTF performed a brief literature review and determined that the benefits of screening for congenital hypothyroidism continue to be well established. This update included a search for new and substantial evidence on the benefits and harms of screening.4 The USPSTF found no new substantial evidence on the benefits and harms of screening for congenital hypothyroidism and, therefore, reaffirms its recommendation that all newborns be screened for congenital hypothyroidism. The 1996 recommendation statement, the 1996 evidence report, and the summary of the updated literature search can be found at http://www.uspreventiveservicestaskforce.org/recommendations.htm.

Recommendations from Other Groups

The American Academy of Pediatrics (AAP) and the American Academy of Family Physicians recommend universal newborn screening for congenital hypothyroidism.2,5 The AAP, in conjunction with the American Thyroid Association and the Lawson Wilkins Pediatric Endocrine Society, published guidelines for screening and treatment of congenital hypothyroidism.2

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