Direct double monoclonal immunoradiometric assay of urinary human growth hormone

Several reports indicate that urinary growth hormone (GH) excretion might reflect central release of the hormone, and that measurement of urinary GH shows promise in the investigation of physiological and pathological GH secretion. We have developed and evaluated a direct immunoradiometric assay (IRMA) in which two monoclonal antibodies are used to measure GH in the urine of children. The detection limit is approximately 0.018 pmol/L for a sample volume of 2 mL. Within- and between-run variations (CVs) were 5.6% and 14.2%, respectively. Analytical recovery and dilution experiments showed the specificity of the method for GH. In normal-stature prepubertal children ages 3-12 years, 24-h urinary GH excretion was 0.189 (SD 0.100) pmol and correlated well with the amount of GH in the first morning miction, which showed wide day-to-day variations. Like others, we found a strong correlation between GH concentrations in serum and urine during stimulation tests with GH-releasing hormone (somatoliberin) and (or) during physiological nocturnal secretion, confirming that urinary GH measurement may be of help in investigating patients (particularly young children) with diseases in which GH secretion is impaired.