Assay of growth hormone levels in human plasma using commercial kits: analysis of some factors influencing the results.

The reliability of growth hormone (GH) assays, performed in 39 different laboratories, using five different immunoassay kits was evaluated. It was found that the variability in GH levels measured by different commercial assay kits may be due to human factors, as well as differences between the kits. The influence of the variation in amount of circulating GH, during provocative testing and spontaneous secretory episodes, on the results of GH assay was also evaluated. It was found that large molecular weight forms of GH may be underestimated by some assay kits.