Measurement of human growth hormone in urine: development and validation of a sensitive and specific assay

A specific solid-phase immunoradiometric assay (IRMA), optimized for maximum sensitivity, has been developed for measurement of human GH (hGH) in urine. The sensitivity varied with sample size, giving a range of 0.001 to 0.003 mU/l for a sample volume of 2 ml. Recovery and dilution experiments, together with chromatography of urine samples, indicate that the method is specific for hGH. Added exogenous hGH was measured with a mean recovery of 101 +/- 10% (S.D.) for 1 ml samples and 87 +/- 8% for 2 ml samples. Measurements of samples diluted at 1:2 and 1:4 gave values of 97.4 and 96.6% respectively of those expected. Cross-reactions of human placental lactogen and prolactin were less than 0.008 and 0.04% respectively on a mol/mol basis. The assay was insensitive to the presence of NaCl (50-500 mmol/l), urea (50-1000 mmol/l), creatinine (1-20 mmol/l), Ca2+ ions (1-20 mmol/l), SO4(2-) ions (1-1000 mmol/l), Mg2+ ions (0.05-50 mmol/l), 0.5-5% (w/v) glucose and a pH range of 6-9. Chromatography of unextracted samples showed that the immunoreactive material in urine eluted in a single homogenous peak with a similar position to monomeric pituitary hGH (22 kDa). Administered hGH (0.002%) was recovered in urine collected over a 2-h period following an intravenous injection. The urine output of hGH showed a good correlation with serum hGH in 18 patients following routine insulin tolerance tests and in 25 patients following an oral glucose tolerance test.(ABSTRACT TRUNCATED AT 250 WORDS)