Text Box: THE RELATION BETWEEN SERUM CONCENTRATIONS OF LEPTIN AND ERYTHROPOIETIN IN HEALTHY AND SICK NEONATES Acunas B1, Vatansever U1, Unlu A2, Ekuklu G3, Sener S2, Pala O1 Trakya University Faculty of Medicine Dept of Pediatrics1, Biophysics2, Public Health3, Edirne, Turkey Objective: It has been reported that leptin significantly stimulates the proliferation and differentiation of yolk sac cells and fetal liver cells and stimulates directly hematopoietic precursors in vitro. Erythropoietin (Epo), is the main factor controlling erythropoiesis in both antenatal and postnatal life and increased levels of Epo have been reported in conditions associated with intrauterine hypoxia, severe growth retardation and perinatal brain damage. The objective of this study was to elucidate the relation between serum concentrations of leptin and erythropoietin in normal and sick neonates. Method: The study group comprised of six groups of infants (n=106). Group 1 included infants that were small for gestational age (SGA) (n=14), Group 2 comprised of infants born premature (n=25). Group 3 included term infants with perinatal asphyxia (n=18). Group 4 comprised of infants of diabetic mothers (n=12). Group 5 included infants delivered with cesarean section (n= 19) and Group 6 included infants born with normal labor (n=18). Blood samples were obtained within 12 hours (S1), 3 (S2) and 7(S3) days after birth to assess serum concentrations of leptin and Epo. Results: Serum concentrations of leptin were significantly lower in Groups 1 and 2 compared to the other groups at study entry (p= 0.002). A decrease in leptin levels was seen in all groups with an advance in postnatal age. There was a significant correlation between baseline leptin levels (log transformed) and birth weight and body mass index (BMI) of neonates (r= 0.32, p=0.001; r= 0.35, p<0.001 respectively). In the stepwise lineer regression model, BMI was the best predictor of leptin concentration ( y= -2.495 + 0.28. BMI). There was no statistically significant difference among the groups with regard to erythropoietin concentrations of S1 and S2. However, erythropoietin levels of S3 remained significantly high (p=0.001) in Group 3 compared to the other groups. A decrease in erythropoietin levels was observed in all groups with an advance in postnatal age. No correlation was observed between leptin levels and erythropoietin concentrations Conclusion: The results of this study confirms previous data that serum leptin concentrations are low in SGA and premature infants and positively correlated with birthweight and BMI, but does not support the possibility that leptin has an association with erythropoietin in healthy and sick neonates. 2332