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Published on: November 20, 2015
High incidence of thyroid dysfunction in preterm infants
Hye Rim Chung1, Choong Ho Shin, Sei Won Yang
1Department of Pediatrics, Seoul National University Bundang Hospital, Seongnam, Korea.
Insights
Repeat thyroid function tests are crucial for preterm infants, as initial results may not reflect true thyroid status. Monitoring is essential, especially for those exposed to iodine variations.
Area of Science:
- Neonatalogy
- Endocrinology
- Pediatric Research
Background:
- Preterm infants (<32 weeks' gestational age) require careful monitoring of thyroid function due to developmental vulnerabilities.
- Thyroid dysfunction in preterm neonates can impact growth and neurodevelopment.
- Establishing reliable thyroid function assessment protocols for this population is critical.
Observation:
- Thyroid function tests, including serum free thyroxine (fT4) and thyrotropin (TSH), were evaluated in 105 preterm infants.
- Initial tests were followed by repeat assessments more than two weeks later to track thyroid status.
- Factors analyzed included gestational age, systemic diseases, nutrition, and iodine exposure.
Findings:
- 30% of infants exhibited low fT4 without elevated TSH, indicating potential subclinical issues.
- 12% were diagnosed with hypothyroidism (low fT4 and high TSH) around 28 days of age.
- Transient TSH elevations with normal fT4 were observed in some infants, particularly after surgical procedures involving iodine.
Implications:
- Repeated thyroid function testing is essential for preterm infants, even with initially normal results.
- Iodine exposure (excessive or insufficient) is a significant factor influencing thyroid dysfunction in this group.
- Early and accurate diagnosis of thyroid dysfunction in preterm infants is vital for timely intervention and management.
Abstract:
To determine the validity of a repeat thyroid function test for preterm infants, and to investigate factors that influence thyroid function of preterm infants, thyroid functions of 105 infants born at <32 weeks' gestational age were evaluated. Initial serum free thyroxine (fT4) and thyrotropin (TSH) levels were measured during the first 10 days of life, and repeated tests were performed more than 2 weeks apart. We analyzed the effects of gestational age, systemic diseases, and nutrition on the development of thyroid dysfunction. Thirty-one infants (30%) had low fT4 levels (<0.7 ng/dL) in the absence of elevated TSH levels (<7 microU/mL). Thirteen infants (12%) had hypothyroidism (fT4 <0.7 ng/dL, TSH >or=10 microU/mL) and mean age at diagnosis was 28+/-17 days. Twelve infants had moderately elevated TSH (TSH 10-30 microU/mL) with normal fT4 levels after 1 week of postnatal life. The history of undergone surgical procedure which needed iodine containing disinfectants was significantly frequent in the infant with hypothyroidism and transient TSH elevation. Repeated thyroid function tests are necessary for preterm infants, even though they initially show normal thyroid function, and are especially important for infants who have been exposed to excessive or insufficient levels of iodine.
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