Late Detection of Thyroid Dysfunction in NICU Patients / 대한주산의학회잡지

ABSTRACT

OBJECTIVE: To evaluate the incidence, the time of detection, classification, and risk factors of thyroid dysfunction in very low birth weight (VLBW) and sick infants in order to help with the diagnosis and treatment of thyroid dysfunction in the neonatal intensive care unit (NICU). METHODS: We reviewed the medical records of 78 infants, who were admitted for more than 1 month in the NICU at Chungbuk National University Hospital from July 2004 through June 2006. In these infants, at least to 2 thyroid function tests were performed, a initial screening whthin 2 weeks of age and a repeated thyroid function test after 2 weeks of age. RESULTS: 1) The study infants were divided into 2 groups, VLBW (birth weight or =1,500 g). 2) In the VLBW groups (n=48), 24 infants (50%) showed thyroid dysfunction. Six infants (12.5%) were detected at initial screening test and all had transient hypothyroxinemia. The remaining 18 infants (37.5%) were detected at repeated tests, most commonly detected at 4~8 weeks of age (n=8). Their types of thyroid dysfunction were primary hypothyroidism (PH) with a delayed marked TSH rise (n=3), PH with a delayed mild TSH rise (n= 7), euthyroid sick syndrome (ESS, n=8), and central hypopituitary hypothyroidism (HH, n=1). 3) In the NVLBW groups (n=30), 11 infants (36.7%) showed thyroid dysfunction. Three infants (10%) were detected at initial screening test, while 8 (26.7%) were detected at repeated tests. Their types of thyroid dysfunction were PH (n=5), ESS (n=3), transient hyperthyrotropinemia (n=2), and HH (n=1). 4) Among 35 infants with thyroid dysfunction, 20 infants (57.1%) were treated with thyroxine. CONCLUSION: Thyroid dysfunction was very common in sick infants in the neonatal intensive care unit, especially in the very low birth weight infants. Often, they were not detected at the initial screening test, but detected at later repeated tests. The repeated thyroid function test need to be performed in infants at risk for late detection of thyroid dysfunction after 2~4 weeks of age.