Study Of the Thyroid Hormone Profile in Preterm Small for Gestational Age and Appropriate for Gestational Age Infants in A Tertiary Care Hospital

Abstract

Background: Thyroid hormone play a key role in normal growth and development of children especially in their first two years of life. Untreated congenital hypothyroidism can lead to intellectual disabilities and developmental abnormalities.5Even transient hypothyroxinaemia in early neonatal period can cause neurologic and mental problems.6Thyroid dysfunction is more common in preterm neonates when compared to term babies. Additional to prematurity, being small for gestational age further affects the cognitive and sensorimotor functions of an infant. There are very few studies that showed altered thyroid hormones in the first week of life in preterm SGA, so further studies are required. We did the present study to compare thyroid hormone profile among preterm SGA and preterm AGA and to see if being SGA makes the preterm babies more susceptible to thyroid dysfunction and if any comorbidities of the preterm newborns have any association with their thyroid hormone profile.
Methods: It was designed to study thyroid hormone profile and frequency of thyroid dysfunction in preterm SGA and AGA infants. Study also assessed the association of neonatal clinical conditions like low APGAR score, intraventricular haemorrhage, necrotising enterocolitis, congenital heart diseases and NICU intervention such as surfactant administration, and use of medications (steroids, dopamine and furosemide) with thyroid hormone profile in preterm SGA and AGA infants. Observational, Cross-Sectional Study was done for 18 Months in Neonatal intensive care unit, Krishna Institute of Medical Sciences,Karad. All preterm newborns (GA <37 Weeks) admitted to the neonatal intensive careunit, Krishna Institute of Medical Sciences, Karad including both preterm SGA and preterm AGA were included in the study. The Thyroid function test was performed on Day 4 of life in preterm SGA and preterm AGA infants in NICU and repeated on Day 14.Thyroid function test (TFT) results, and  neonatal demographic and clinical factors were analysed to identify thyroid dysfunction in preterm SGA and AGA infants
Results: Mean value of TSH was measured to be 5.81mU/L in the SGA group whereas it wasrelatively less in the AGA group with mean value of 4.42 mU/L. The p value was <0.0001 which was found to be statistically significant. Mean FT4 value in SGA preterms was 1.69ng/dl while in AGA preterms was 1.97ng/dl. In this study transient hypothyroidism was seen in 1 SGA preterm and 2 AGA preterms, transient hypothyroxinaemia was seen in 3 SGA preterms and 5 AGA preterms, hyperthyrotropinemia was seen 4 each in SGA and AGA preterms and 1 case of delayed TSH elevation in preterm SGA group though none was statistically significant. We observed statistically significant higher TSH (7.46±0.66) in low APGAR preterm SGA babies and statistically significant higher TSH (7.74±1.22) in low APGAR preterm AGA babies. It was observed that TSH was on higher side in severe intraventricular haemorrhage (6.65±1.8) in preterm SGA group and (6.65±1.8) in preterm AGA group. It was statistically significant with p value 0.003 in AGA group.Clinical conditions like CHD, IVH NEC did not affect FT4 values in preterm SGA andAGA group. Medications like surfactant administration, usage of steroids, dopamine and furosemide did not affect TSH and FT4 concentration in preterm SGA and AGA in the present study.
Conclusion: Preterm SGA newborns had significantly higher TSH concentrations within the normal range and FT4 was on the lower side compared to AGA preterm group. Repeat screening done at day of life 14 showed various thyroid dysfunction in bothSGA and AGA preterm groups. Newborn screening for thyroid abnormalities and repeated follow upfor bothpreterm SGA and AGA, with special consideration to preterms with comorbidities is advisable.