Dose dependency of the serum bio/immuno GH ratio in childen during pharmacological secretion tests

E. A. Chaler, P. Travaglino, S. Pagani, E. Bozzola, R. Marino, E. Berensztein, M. Maceiras, M. Tauber, M. A. Rivarola, A. Belgorosky, Mauro Bozzola

Research output: Contribution to journalArticlepeer-review

Abstract

Dissociation between GH bioactivity (bio-GH) and GH immunoactivity (immuno-GH) is due to the heterogeneity of the molecule: the measurements do not always provide reliable information on the bio-GH. We studied the ratio of bio-GH and immuno-GH during pharmacological secretion tests in 211 sera to study the concentration-response curve of the assay (C1), 16 samples of normally growing subjects with idiopathic short stature (C2), 13 samples from patients with GH deficiency (GHD1) and 6 samples of 3 patients with GHD and normal provocative tests (GHD2). GH bioactivity was determined by the Nb 2 cell proliferation assay (bio-GH) and immuno-GH by a time-resolved immunofluorometric assay (IFMA) (immuno-GH). A non-linear negative relationship between the serum bio-GH /immuno-GH ratio and serum immuno-GH was observed in C1. In log-log plotting representation, two cut-off lines were drawn: a vertical cut-off line separating above-below cut-off serum peak immuno-GH values in provocative tests, and a diagonal cut-off line separating normal-abnormal serum bio-GH/immuno-GH ratio; four areas were defined. GHD1 had normal ratios, but below cut-off peak immuno-GH responses. P2 and P3 of Group GHD2 had abnormal ratios in samples with low serum immuno-GH but only P2 had autosomal dominant mutation. P1 had the same autosomal dominant isolated GHD as P2 but a low normal ratio. Our data underline the importance of relatively low serum GH concentrations in mediating GH biological actions. An abnormal serum bio-GH/immuno-GH ratio might explain certain cases of GHD and might be useful in detecting abnormal circulating isoforms of GH in patients with growth failure.

Original languageEnglish
Pages (from-to)109-114
Number of pages6
JournalJournal of Endocrinological Investigation
Volume29
Issue number2
Publication statusPublished - Feb 2006

Keywords

  • GH bioactivity and immunoactivity
  • GH deficiency
  • Nb2 cell bioassay
  • Short children

ASJC Scopus subject areas

  • Endocrinology

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