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.
Female ; Gestational Age ; Humans ; Hypothyroidism/*diagnosis/epidemiology/metabolism ; Incidence ; Infant, Newborn ; Infant, Premature ; Infant, Premature, Diseases/*diagnosis/epidemiology/metabolism ; Pregnancy ; Thyroid Function Tests ; Thyrotropin/*blood ; Thyroxine/*blood

PURPOSE: We hypothesized that parenteral nutrition associated cholestasis (PNAC) would be more severe in small for gestational age (SGA) compared with appropriate for gestational age (AGA) very low birth weight (VLBW) infants. MATERIALS AND METHODS: Sixty-one VLBW infants were diagnosed as PNAC with exposure to parenteral nutrition with elevation of direct bilirubin > or =2 mg/dL for > or =14 days. Twenty-one SGA infants and 40 AGA infants matched for gestation were compared. RESULTS: Compared with AGA infants, PNAC in SGA infants was diagnosed earlier (25+/-7 days vs. 35+/-14 days, p=0.002) and persisted longer (62+/-36 days vs. 46+/-27 days, p=0.048). Severe PNAC, defined as persistent elevation of direct bilirubin > or =4 mg/dL for more than 1 month with elevation of liver enzymes, was more frequent in SGA than in AGA infants (61% vs. 35%, p=0.018). The serum total bilirubin and direct bilirubin levels during the 13 weeks of life were significantly different in SGA compared with AGA infants. SGA infants had more frequent (76% vs. 50%, p=0.046), and persistent elevation of alanine aminotransferase. CONCLUSION: The clinical course of PNAC is more persistent and severe in SGA infants. Careful monitoring and treatment are required for SGA infants.
Bilirubin/blood ; Case-Control Studies ; Cholestasis/diagnosis/epidemiology/*etiology ; Comorbidity ; Female ; Humans ; Infant, Newborn ; Infant, Premature, Diseases/epidemiology/etiology ; *Infant, Small for Gestational Age ; Infant, Very Low Birth Weight ; Liver/metabolism/physiopathology ; Male ; Parenteral Nutrition/*adverse effects