Objective To evaluate the thyroid functions of preterm infants.
Methods Data about thyroid functions (fT4, TSH) were collected retrospectively from 428 preterm infants less than 34 weeks of gestation, who were born between 2006 and 2009.
Results The mean gestational age of the study group was 30.5±2.4 (23.9–33.9) weeks, the mean birth weight was 1339±496 (496–3190)g. The study group was divided into three subgroups according to gestational weeks (< 28 wk, n=79; 28–31 6/7 wk, n=204; 32–33 6/7 wk, n=145). Twenty five percent of the infants were small for gestational age (SGA). Mean age at first thyroid function evaluation was 18.3±12.5 days. Mean fT4 levels were 12.0±3.1, 14.1±3.3 and 17.7±3.9 pmol/L in three subgroups, respectively and significantly lower in infants < 28 weeks. In all subgroups SGA infants had lower fT4 levels, but it was significantly lower in only 28–31 6/7 and 32–33 6/7 weeks but not in < 28 weeks subgroup.Overall, the prevalence of hypothyroxinemia and hypothyroidism were 25% and 0.8%, respectively in the first evaluation. 17.6% of infants < 28 weeks had hypothyroxinemia (n=13) and all of them were treated. In the total group levothyroxine treatment was given to 51 (11.9%) infants. Mean treatment period was 1.6±1.2 years.
Conclusion Free T4 levels were lower in the early gestational age subgroups. SGA infants had lower fT4 levels.