Thyroid hormones are critical for normal growth and neurodevelopment. Abnormalities of thyroid functions tests (TFT) are frequently seen in premature infants, physiological hypothyroxinemia being the most common (70%). Clinical and subclinical hypothyroidism is common (0.3–2.5%) in woman who are in conceptional age or pregnant. Maternal hypothyroidism is known to have an adverse impact on the developing fetus. In this study we aim to identify the rate of abnormalities of TFT, its association with morbidities and impact on long term neurodevelopment.
Material and method In this retrospective study, rate of abnormalities of TFT, its association with morbidities and neurodevelopment is investigated in 139 premature babies admitted to neonatal intensive care unit in Uludag Universitiy Medical Faculty between January 2009 and January 2012.
Results Mean gestational weeks and birth weights of infants were 31.3 ± 2.9 weeks 1667 ±707 gr. Fourty one patients (24%) had TFT abnormality, 53.6% had transient TSH elevation, 22% had primary hypothyroidism, 22% had non-thyroidal disease and 2.4% had transient hypothyroxinemia. Fourty seven percent of SGA babies and, 26% of AGA babies had TFT abnormalities, difference was not statistically significant. Most common TFT abnormality was found to be transient TSH elevation in SGA and AGA babies. Mothers of 8 patients had maternal hypothyroidism. Five of these babies (63.5%) had TFT abnormality (p = 0.049). Mean head circumference in 18 months of age in normal TFT group was 46.3 cm ± 1.6 compared to babies with abnormal TFT whose mean head circumference was 45 cm ± 2.4 at the same age, difference was statistically significant. There were no statistically significant difference between groups for antropometric values in 6, 9, 12 moths and neurodevelopmental evaluation.
Conclusion TFT abnormalities are frequent in prematüre babies and it is one of the most common causes of preventable mental retardation. In neonates, even transient hypothyroidism is associated with poor neurodevelopmental outcome, hence it must be treated urgently. As also detected in our study, maternal hypothyroidism is associated with increased neonatal hypothyroidism and these babies must be managed closely in postnatal period. Although not statistically significant, SGA babies were found to have increased rate of hypothyroidism. Further investigation with larger number of patients is necessary.