THE IMPACT OF GENDER AND PUBERTY ON REFERENCE VALUES FOR URINARY GROWTH-HORMONE EXCRETION - A STUDY OF 3 MORNING URINE SAMPLES IN 517 HEALTHY-CHILDREN AND ADULTS

Some recent studies have indicated that measurement of urinary GH (U-G H) excretion may be a useful tool for the evaluation of GH insufficien cy in children with growth disorders, although some investigators are skeptical about the diagnostic value of U-GH. Most current assays are only available for specific laboratories or require time-intensive pre treatments of the specimens. This limits the possibility for many cent ers to compare their patients' data with others or to establish their own reference ranges for U-GH excretion. Therefore, we investigated th e performance of a commercially available kit, which allows direct mea surement of U-GH in untreated urine specimens. We established a refere nce range for the geometric mean of 3 morning urine samples in 446 hea lthy children and 71 adults. U-GH could be determined in all but 9 of 1526 samples (99.4%). U-GH excretion was significantly dependent on pu bertal maturation (P < 0.0001) and sex (P < 0.001), whereas age had no significant influence in the prepubertal group (P > 0.3). Peak values occurred in Tanner stages 3 and 4 (369 and 391 pg/h in females; 503 a nd 882 pg/h in males), corresponding to an age interval of 11-18 yr in boys and 9-15 yr in girls. Short collection periods (<6 h) were relat ed to low values for U-GH excretion (nanograms per night; P < 0.02). T his time effect disappeared if U-GH excretion was expressed as picogra ms per h. If U-GH was related to creatinine output, there was a decrea se in U-GH excretion during prepuberty, a blunting of the pubertal pea k, and lower values in adults than in prepubertal children (P < 0.0002 ). The intraindividual variation in U-GH excretion (picograms per h) r anged from 40-61%, constituting approximately two thirds of the interi ndividual variation. This variation was not lowered by relating U-GH t o creatinine. We conclude that the assay was suitable for measurement of U-GH excretion in virtually all healthy volunteers. Sex and puberta l stage as well as urinary volume and clock times for collection perio ds should be registered when establishing a reference range for U-GH e xcretion and applying it for clinical purposes. Our reference values m ay be useful for further studies of patients with GH disorders.