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Wegmann MG, Jensen RB, Thankamony A, Frystyk J, Roche E, Hoey H, Kirk J, Shaikh G, Ivarsson SA, Söder O, Dunger DB, Juul A. Increases in Bioactive IGF do not Parallel Increases in Total IGF-I During Growth Hormone Treatment of Children Born SGA. J Clin Endocrinol Metab 2020; 105:5608612. [PMID: 31665326 DOI: 10.1210/clinem/dgz118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 10/17/2019] [Indexed: 12/16/2022]
Abstract
BACKGROUND Some children born small for gestational age (SGA) experience supra-physiological insulin-like growth factor-I (IGF-I) concentrations during GH treatment. However, measurements of total IGF-I concentrations may not reflect the bioactive fraction of IGF-I which reaches the IGF-I receptor at target organs. We examined endogenous IGF-bioactivity using an IGF-I kinase receptor activation (KIRA) assay that measures the ability of IGF-I to activate the IGF-IR in vitro. AIM To compare responses of bioactive IGF and total IGF-I concentrations in short GH treated SGA children in the North European Small for Gestational Age Study (NESGAS). MATERIAL AND METHOD In NESGAS, short SGA children (n = 101, 61 males) received GH at 67 µg/kg/day for 1 year. IGF-I concentrations were measured by Immulite immunoassay and bioactive IGF by in-house KIRA assay. RESULTS Bioactive IGF increased with age in healthy pre-pubertal children (n = 94). SGA children had low-normal bioactive IGF levels at baseline (-0.12 (1.8 SD), increasing significantly after one year of high-dose GH treatment to 1.1 (1.4) SD, P < 0.01. Following high-dose GH, 68% (n = 65) of SGA children had a total IGF-I concentration >2SD (mean IGF-I 2.8 SDS), whereas only 15% (n = 15) had levels of bioactive IGF slightly above normal reference values. At baseline, bioactive IGF (SDS) was significantly correlated to height (SDS) (r = 0.29, P = 0.005), in contrast to IGF-I (SDS) (r = 0.17, P = 0.10). IGF-I (SDS) was inversely correlated to delta height (SDS) after one year of high-dose GH treatment (r = -0.22, P = 0.02). CONCLUSION In contrast to total IGF-I concentrations, bioactive IGF stayed within the normal reference ranges for most SGA children during the first year of GH treatment.
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Affiliation(s)
| | - Rikke Beck Jensen
- Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Denmark
| | - Ajay Thankamony
- Department of Pediatrics, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Jan Frystyk
- Medical Research Laboratory, Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Endocrine Research Unit, Department of Endocrinology, Odense University Hospital & Department of Clinical Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
| | - Edna Roche
- Department of Pediatrics, The National Children's Hospital, Trinity College Dublin, The University of Dublin, Dublin, Ireland
| | - Hilary Hoey
- Department of Pediatrics, The National Children's Hospital, Trinity College Dublin, The University of Dublin, Dublin, Ireland
| | - Jeremy Kirk
- Department of Endocrinology, Birmingham Children's Hospital, Birmingham, United Kingdom
| | - Guftar Shaikh
- Department of Endocrinology, Royal Hospital for Children, Glasgow, United Kingdom
| | - Sten-A Ivarsson
- Department of Clinical Sciences, Endocrine and Diabetes Unit, University of Lund, Lund, Sweden
| | - Olle Söder
- Pediatric Endocrinology Unit, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden
| | - David B Dunger
- Department of Pediatrics, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Anders Juul
- Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Denmark
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