Thyroid-function assessment by use of enzyme immunoassays

We used an enzyme immunoassay to determine the normal reference intervals for thyroxin, triiodothyronine, and thyrotropin in groups of children, ranging from newborns to 15-year-olds. Results compared well with those by radioimmunoassay. There were no substantial differences between plasma and serum samples for thyroxin and triiodothyronine, but thyrotropin concentrations differed significantly (p less than 0.05, n = 20 each).