The levels of serum enzymes, plasma proteins and lipids in normal infants and small children.

A group of 291 children aged 3 weeks to 6 1/2 years was examined at a public maternal and child health center and 260 of them - who were considered to be healthy - were included in the present study. By venipuncture, serum was obtained for the analysis of 6 enzymes, and plasma for the estimation of 9 proteins and for lipid analyses. In different age groups, high levels were found for alkaline phosphatase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, creatine kinase and gamma-glutamyl transferase. Haptoglobin, alpha 1-antitrypsin, prealbumin and transferrin were present at low concentrations during the first months of life. Transferrin rose later in childhood to above adult levels. Only immunoglobulin M showed a sex difference, with higher values for girls. Breast-fed infants had higher (non-fasting) concentrations of cholesterol and triglycerides than formula-fed babies, and they also had higher levels of aspartate aminotransferase and alanine aminotransferase.