J Clin Res Pediatr Endocrinol. Ahead of Print: JCRPE-65265 | DOI: 10.4274/jcrpe.galenos.2022.2022-2-1

Thyroid Function in 509 Premature Newborns Below 31 Weeks of Gestational Age: Evaluation and Follow-up

Ariadna Campos-martorell¹, Alicia Montaner Ramon², Karla Narváez Barros³, Jose Luis Marin Soria⁴, Rosa Maria López Galera⁴, Diego Yeste Fernández⁵, María Clemente León^6
1Pediatric Endocrinology Unit. Vall d’Hebron University Hospital. Barcelona, Spain. Autonomous University of Barcelona. Barcelona, Spain
²Neonatal Unit. Vall d’Hebron University Hospital. Barcelona, Spain
³Pediatric Endocrinology Unit. Hospital del Mar. Barcelona, Spain
⁴Neonatal Screening Program of Catalonia. Inborn Errors Metabolism Unit Biochemistry and Molecular Genetics Department Center for Biomedical Diagnosis (CDB) Hospital Clinic. Barcelona. Spain School of Medicine. University of Barcelona. Spain
⁵Pediatric Endocrinology Unit. Vall d’Hebron University Hospital. Barcelona, Spain. Vall d’Hebron Research Institute. Paediatric Endocrinology. Vall d’Hebron University Hospital. Barcelona, Spain. Autonomous University of Barcelona. Barcelona, Spain
⁶Pediatric Endocrinology Unit. Vall d’Hebron University Hospital. Barcelona, Spain. Vall d’Hebron Research Institute. Paedriatic Endocrinology. Vall d’Hebron University Hospital. Barcelona, Spain. Autonomous University of Barcelona. Barcelona, Spain

INTRODUCTION: Preterm and low birth weight (LBW) neonates could present thyroid dysfunction during a critical period for neurodevelopment. These alterations can be missed in the congenital hypothyroidism screening which only measures TSH. The objective of this study was to evaluate a protocol for thyroid function screening (TFS) 6 years after its implementation.
METHODS: Serum TSH and free thyroxine (FT4) were performed during the second week of life in neonates below 31 weeks. Patients with abnormal TFS (FT4<0.8ng/dL and/or TSH>5mU/L) were followed up with repeated tests until normal levels were reported. Patients who were still on levothyroxine at 3 years of age were re-evaluated.
RESULTS: 509 neonates were included. Thyroid dysfunction was detected in 170 neonates (33%); congenital hypothyroidism (CH): 20 (3.9%) [typical CH: 1; delayed TSH CH: 19]; hypothyroxinemia of prematurity (HOP): 15 (2.9%); and transient hyperthyrotropinemia: 135 (26.5%). Twenty-one neonates (4.1%) were treated (20 for CH and 1 for HOP). At 3-year follow-up only 3 patients were diagnosed with permanent CH and still need treatment. LBW presented TSH levels higher than those with adequate weight.
DISCUSSION AND CONCLUSION: This protocol was able to detect thyroid dysfunction in preterm neonates who were not identified by the current program based on TSH determination in whole-blood. This thyroid dysfunction seems to resolve spontaneously in a few months in the great majority of neonates, but in some cases levothyroxine could be needed. There is a critical need for specific guidelines regarding the follow-up and reevaluation of transient CH in preterm neonates.

Keywords: preterm newborn, low birth weight, congenital hypothyroidism, hypothyroxinemia of prematurity, delayed TSH rise

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