Growth hormone (GH) determinations by RIA and IFA during GH stimulation tests in children with short stature

Growth hormone deficiency (GHD) as a syndrome comprises multiple pathogenetically distinct entities caused by disorders of secretion or peripherial action of growth hormone (GH). Confirmation of the diagnosis of GH deficiency in children is based on provocative testing for human growth hormone (hGH). Immunofunctional assay (IFA) allows quantitation of only biological active GH forms in circulation. The aim of this study was to compare the results of GH determinations by radioimmunoassay (RIA) and IFA, and to establish cut-off-levels for IFA in insulin tolerance test (ITT). We have investigated 32 children (30 males and 2 females) with short stature. All patients underwent insulin tolerance test (ITT), GH was measured in duplicate by radioimmunoassay (RIA, Seria) and IFA (DSL). Children with peak GH concentration below 10 ng/ml in ITT (by RIA) underwent arginin tolerance test (ATT, arginin 0,5 g/kg). The correlation between the results of growth hormone determination by radioimmunoassay and immunofunctional assay was excellent and cut-off-level in stimulatory test was established for the immunofunctional assay.