92 MEASUREMENT OF URINARY GROWTH HORMONE (uGH) BY A SENSITIBE BNZYME IMMUNOMETRIC ASSAY (EIA) IN CHILDREN

Abstract

An EIA developed for the measurement of serum GH, vas adapted for the measurement of uGH. Due to the very low levels of GH, urine saaples are routinely dialyzed and concentrated at least 15 fold by centrifugal ultrafiltration. Urine samples collected in plastic tubes containing BSA (1g/l) are stored at -20°C until analyzed for GH and creatinine (CR). Under these conditions GH is stable for at least 2 months. Mean recovery of GH after dialysis and concentration is 91.4%. The sensitivity of the assay is 0.4 pg/tube. The intraassay and interassay coefficients of variation are respectively 4.9% and 5.5% at a concentration of 4.5 pg/ml. The centrifugal ultrafiltration step requires approxiaately 45′ per batch. Using this aethod we analyzed first-morning urine samples of healthy children and of children referred for short stature. The results in the healthy children vary froa 5 to 100 ng GH/g CR. In children with documented GH deficiency results are <3 ng GH/g CR. In children with intermediate GH response to ITT and/or ARG results range froa 3 to 6 ng GH/g CR. Furthermore, we found a highly significant correlation between uGH and peak serum GH during ITT or ARG provocation tests. From our results we conclude that the measurement of uGH in morning urine reflects night-GH production. The effectiveness of this parameter for diagnostic purpose has to be further studied, due to the large day to day variation of measured uGH in individual children.