Endocrine Abstracts

Objective: All neonates should be screened for congenital hypothyroidism in the first week of their lives. To evaluate the reliability of thyroid function tests in neonates who undergo exchange transfusion (ET), we decided to study the alteration of thyroid hormones after ET in term neonates.Method: From April 2001 to August 2001, eighteen full term neonates (gestation age > 37 weeks) undergoing ET due to hyperbilirubinemia at neonatal wards of Al-Zahra and Shahid-Beheshti hospitals, both are teaching hospitals affiliated to Isfahan University of Medical Sciences, Iran, were studied. All ETs were performed using a double volume exchange of adult donor blood. The age of subjects was five days or more. The patients had not Rh disease and seemed well. Thyroid function (T3, T4, TSH) was evaluated before the exchange (pre-ET), at the conclusion of the ET (post-ET) and seven days later. Results were analyzed with the Student t test and Wilcoxon test. P values less than 0.05 were considered significant.Results: The mean pre-ET, T4 and TSH concentrations were significantly higher than in donor blood but the mean pre-ET, T3 concentration was not statistically differing from donor blood. At the end of exchange (post-ET), the mean T4 and TSH concentrations dropped and statistically differed from pre-ET values whereas the mean post-ET, T4 and TSH were still significantly higher than the donor blood. The post-ET, T3 value was not significantly different from pre-ET, T3 and T3 of donor blood. After seven days, the mean T4 and TSH concentrations increased and statistically reached to pre-ET, T4 and TSH but at this time the mean T3 concentration was significantly higher than pre-ET value.Conclusion: The results of our study showed that there was a significant decrease in concentrations of T4 and TSH at the end of ET but no difference at seven days later. Therefore, we suggest that the screening of congenital hypothyroidism should be performed either before the ET or after one-week Post Exchange transfusion.