Spontaneous changes in growth hormone and insulin levels in newborn infants.

Ten term, normally grown newborn infants aged 3-5 days with hyperbilirubinaemia due to rhesus or ABO incompatibility have been studied. Blood samples were taken via an umbilical venous catheter at 10 minute intervals in order to study spontaneous changes in growth hormone, insulin, glucose and free fatty acid concentration. Mean plasma GH, insulin and glucose concentrations remained unchanged, but the FFA level rose, due probably to the low room temperature at which the investigations were performed. Analysis of individual changes showed large and bidirectional alterations in GH and insulin, which were much greater than the error of the analytical methods. The findings should be considered in the evaluation of diagnostic investigations performed on newborn infants.