Plasma beta-endorphin concentrations in neonates associated with acute stress

Plasma beta-endorphin concentrations were measured in two groups of neonates. The control group (group 1) consisted of 20 infants with a mean gestational age of 31.5 +/- 0.6 weeks and a mean birth weight of 1,720 +/- 135 g. Blood samples were collected at a mean postnatal age of 1.0 +/- 0.3 days. Group 2 consisted of 23 infants with clinical evidence of acute illness and associated significant stress who had a mean gestational age of 33.2 +/- 1.1 weeks and a mean birth weight of 2,075 +/- 225 g. Their blood samples were collected at a mean postnatal age of 3.4 +/- 1.3 days. The mean beta-endorphin concentration in group 1 was 27.8 +/- 6 pg/ml and 63.9 +/- 4.2 pg/ml in group 2 (p less than 0.05). No correlation was observed for gestation or birth weight and beta-endorphin concentrations in group 1; however, in group 2 a positive correlation was seen for gestational age and plasma beta-endorphin concentrations (r = 0.4411) suggesting an increased release of plasma beta-endorphin with increasing gestation when faced with significant clinical stress.