THE DIAGNOSTIC-VALUE OF INTEGRATED GROWTH-HORMONE SECRETION STUDIES SHORTER THAN 24 HOURS IN NORMAL-GROWING AND SHORT-GROWING CHILDREN

Spontaneous growth hormone (GH) secretion is evaluated by measurement of the 24-hour integrated concentration of GH (24-hour IC-GH), a major diagnostic procedure, or by shorter protocols such as monitoring 6 h during sleep. We have evaluated several possibilities for shortening t he procedure by comparing the results of an abbreviated procedure to t he 24-hour IC-GH studies. The study population consisted of 50 childre n with classic GH deficiency (group GHD), determined by provocative te sting, and 45 children who had a subnormal secretion of GH (group N), determined by low 24-hour IC-GH but normal GH provocative tests. Twent y-two children of normal height and stature served as a control group. All the children were prepubertal. while there was no overlap between the lower 5th percentile of the 24-hour IC-GH of the control subjects (3.3 mug/l) and the upper 97th percentile of the 24-hour IC-GHs of th e N and GHD groups (2.9 and 2.7 mug/l, respectively), there was a cons iderable overlap between the IC-GH of control subjects and that of the GHD and N groups measured in all the abbreviated blood withdrawal pro tocols, except for the 10-hour daytime and the 12-hour nighttime proto cols of the GHD patients. It should be noted that there was only a sma ll overlap between the control and the GHD groups during the 12-hour d aytime protocol. We have found that the longer the blood collection pe riod the greater the sensitivity and the specificity. We conclude that the 24-hour IC-GH test is the best diagnostic tool for identifying ch ildren with subnormal GH secretion.