Continuing efforts to standardize measured serum growth hormone values in Japan

DETERMINATION of growth hormone (GH) levels in serum samples is essential for diagnosis of GH deficiency and excess In clinical practice, GH levels have been determined by immunological methods including radioimmunoassay and enzyme immunoassay. In Japan, several reagents to measure serum GH (GH assay kits) have been commercially available. Until 2005, measured GH values in individual sera varied significantly among GH assay kits. To deal with the variations, we as the Study Committee for GH and Its Related Factors, The Foundation for Growth Science, Japan collaborated with the Study Group for Hypothalamo-Pituitary Disorders of the Ministry of Health, Labour and Welfare (MHLW), Japan and the suppliers of GH assay kits, and provided the formulas to adjust the measured values to their average. Since the majority of discrepancies in the measured values were attributed to the unequal potencies of the in-house GH standards of the suppliers, the unified recombinant human GH (rhGH)-based standards were introduced to all GH assay kits in 2005 [4-6]. As the result, the discrepancies in measured values among them became