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348 Circulating PYY, Ghrelin, Leptin and Adiponectin Concentrations in Preterm Infants at Discharge from the Neonatal Unit

Background: Preterm infants are often in negative energy balance during the neonatal period. The aim of the present study was to determine the circulating concentrations of hormones involved in the regulation of metabolism, PYY, ghrelin, leptin and adiponectin, in preterm infants at discharge and to examine whether these hormones are interrelated with each other or correlated with the infants' anthropometric parameters, food intake and growth rates.Materials and Methods: Serum levels of PYY, ghrelin, leptin and adiponectin were measured by RIA in 62 preterm infants (gestational age 32.0±2.1 weeks, postnatal age 40.9±14.8 days) and 15 fullterm infants of a comparable postnatal age. All the infants were formula-fed on demand.Results: Preterm infants had higher PYY (1126.2±215.4 pg/ml, p<0.001) and ghrelin (721.7±98.0 pg/ml, p<0.001), and lower adiponectin levels (40.8±15.3 mcg/ml, p<0.01) than term infants (825.3±234.4, 602.4±93.7 and 53.1±16.0, respectively). Serum leptin concentrations did not differ significantly between preterm (0.1–15.6, median 1.2 mcg/L) and term infants (0.1–9.7, median 1.2 mcg/L). A correlation between the hormones studied was present only between serum PYY and ghrelin levels (r=0.50, p<0.001). In the entire study population, serum PYY concentrations were negatively correlated, whereas adiponectin concentrations were positively correlated, with gestational age, the infants' anthropometric measurements (birthweight, body weight, body length, BMI and head circumference) and the difference in body weight z-score. Ghrelin levels were negatively correlated with gestational age, the infants' anthropometric measurements and the difference in body length z-score. No correlation between serum leptin levels and any of the above variables was recorded. The concentrations of all the hormones studied were not correlated with the infants' caloric intake or weight gain.Conclusions: These findings indicate that PYY and ghrelin are increased in preterm infants, possibly to compensate for the negative energy balance. Adiponectin may have a role in the infants' growth.