All issues > Volume 41(10); 1998

Original Article

J Korean Pediatr Soc. 1998;41(10):1324-1328. Published online October 15, 1998.

Thyroid Hormone Concentrations in Preterm Infants

Sung Keun SK Moon¹, Jeong Nyun JN Kim¹, Mi Jung MJ Park¹, Myung Jae MJ Choi¹, Chrul Young CY Chung¹

¹Deparment of Pediatrics, InJe University, College of Medicine, Seoul, Korea

Correspondence Jeong Nyun JN Kim ,Email: 1

Abstract

Purpose
: To establish reference ranges for thyroid hormone concentrations in premature infants, we measured T4 and thyroid stimulating hormone(TSH) concentrations and analyzed the relation to gestational age and birth weight.
Methods
: Serum T4 and TSH concentrations were measured by radioimmunoassay for 391 premature infants born in Sanggye Paik Hospital for two years and eight months.
Results
: Gestational age of the subjects was 33.3±2.4 weeks(range : 26-37 weeks). Birth weight was 2,016±520g(range : 880-3,510g). Sampling date was 10.5±8.6 day(median value 8 day). Serum T4 concentrations for the gestational age 26 to 28, 29 to 31, 32 to 34 and 35 to 37 week groups were 4.8±3.6, 5.6±3.6, 6.4±4.4 and 7.0±4.6μg/dl, respectively. Serum T4 concentrations for the birth weight below 1,500, 1,500 to 1,999, 2,000 to 2,499 and above 2,500g groups were 5.7±3.8, 5.8±3.6, 6.4±4.6 and 8.1±5.1μg/dl, respectively. Serum TSH concentrations for the gestational age 26 to 28, 29 to 31, 32 to 34 and 35-37 week groups were 6.5±3.0, 7.2±6.1, 5.8±5.0 and 5.6±5.1 mIU/ml, respectively. Serum TSH concentrations(mean±SD) for the birth weight below 1,500, 1,500 to 1,999, 2,000 to 2,499, above 2,500g groups were 8.3±6.8, 5.7±4.3l, 5.5±5.1 and 5.6±5.2 mIU/ml, respectively. Serum T4 concentrations correlated positively with gestational age(y=0.31x - 3.7, R2=0.03, P<0.05) and birth weight(y=0.001x＋3.33, R2=0.33, P<0.05). Serum TSH concentrations correlated negatively with gestational age(y=-0.25x＋16.1, R2=0.01) and birth weight(y= -0.001x＋10.6, R2=0.01).
Conclusion
: Serum T4 concentration in premature infants positively correlated with gestational age and birth weight. Transient elevation of serum TSH concentration was normalized at follow- up test. We recommend that a reference value should be set according to gestational age and birth weight.

Keywords :Premature infants, T4, Thyroid stimulating hormone, TSH