High incidence of thyroid dysfunction in preterm infants

• Published in: Journal of Korean medical science Vol. 24; no. 4; pp. 627 - 631
• Main Authors: Chung, Hye Rim, Shin, Choong Ho, Yang, Sei Won, Choi, Chang Won, Kim, Beyong Il, Kim, Ee Kyung, Kim, Han Suk, Choi, Jung Hwan
• Format: Journal Article
• Language: English
• Published: Korea (South) The Korean Academy of Medical Sciences 01-08-2009; 대한의학회
• Subjects: Female; Gestational Age; Humans; Hypothyroidism - diagnosis; Hypothyroidism - epidemiology; Hypothyroidism - metabolism; Incidence; Infant, Newborn; Infant, Premature; Infant, Premature, Diseases - diagnosis; Infant, Premature, Diseases - epidemiology; Infant, Premature, Diseases - metabolism; Original; Pregnancy; Thyroid Function Tests; Thyrotropin - blood; Thyroxine - blood; 의학일반; Hypothyroidism; Preterm Infant; Thyroid hormones
• ISSN: 1011-8934; 1598-6357
• DOI: 10.3346/jkms.2009.24.4.627

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.