Results of thyroid function tests in premature infants

Abstract

Introduction: To determine the rate, etiology and morbidity association of disorders of thyroid function tests (TFTs) in premature babies.Materials and Methods: A total of 139 premature babies who were admitted to Uludag University Faculty of Medicine Hospital Neonatal Intensive Care Unit between January 2009 and January 2012 were included in this study. Prenatal, natal and postnatal characteristics along with TFTs results were recorded. TFTs were performed for all patients in the first and third weeks of life. Thyroid stimulation hormone (TSH) values of > 10 IU/L was considered elevated. Free T3 and T4 levels were evaluated according to laboratory cut-off values. Weight, height and head circumference values of all individuals with and without the diagnosis of hypothyroidism on the 6th, 12th, and 18th months of their polyclinic follow-ups.Results: Abnormal TFTs were detected in 41 (24%) patients. Twenty two patients (53%) had transient TSH elevation, 9 (22%) had primary hypothyroidism, 9 (22%) had non-thyroidal disease and 1 (2.4%) had transient hypothyroxinemia. Among morbidities, respiratory distress syndrome rate was found to be significantly higher in patients with thyroid function disorders (p=0.007). The rate of thyroid function disorders in patients with mothers with hypothyroidism was significantly more frequent compared to patients without maternal hypothyroidism (p=0.049). The mean head circumference in 18 month was significantly lower in patients with abnormal TFTs (p=0.047).Conclusions: Thyroid function disorders are common morbidities in premature babies and are important for neuromotor development. Maternal thyroid function disorder can lead to impairment of TFTs in infants. Thyroid function tests should be performed in all premature babies and hypotyhroidism should be treated. Avoidance of iodine exposure in premature infants can reduce the rate of abnormal TFTs and transient hypothyroidism.