Reproducibility of growth hormone testing procedures: A comparison between 24-hour integrated concentration and pharmacological stimulation

The purpose of this study was to compare the reproducibility of two approaches to the evaluation of GH secretion: the integrated concentration of GH (IC-GH), a physiological test of GH secretion, and pharmacological stimulation tests. IC-GH was determined in 40 poorly growing children twice within 4 weeks. The first and second IC-GH were highly correlated r = 0.859, P < 0.001. One hundred and thirteen poorly growing children underwent pharmacological GH stimulation tests twice within 6 weeks. A moderate correlation was found between the first and second pharmacological test r = 0.524, P < 0.01. Among the three pharmacological stimuli studied, clonidine (n = 81) had the highest reproducibility followed by arginine (n = 20), and insulin (n = 12). We conclude that IC-GH is more consistently reproducible than the GH response to repeated pharmacological stimulation.