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A novel mutation in a patient with insulin-like growth factor 1 (IGF1) deficiency
  1. G Bonapace,
  2. D Concolino,
  3. S Formicola,
  4. P Strisciuglio
  1. Department of Pediatrics, Faculty of Medicine, University Magna Graecia of Catanzaro, 88100 Italy
  1. Correspondence to:
 Pietro Strisciuglio
 MD, Department of Pediatrics, University Magna Graecia of Catanzaro, c/o Ospedale Civile A. Pugliese, Viale Pio X, 88100 Catanzaro, Italy;

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The insulin-like growth factors (IGFs; somatomedins) comprise a family of peptides that play important roles in mammalian growth and development. The principal members of this family are IGF1 and IGF2. IGF1 (somatomedin C), a 70 residue basic polypeptide, mediates many of the growth promoting actions of growth hormone (GH) and has metabolic and mitogenic effects.1 The major source of circulating IGF1 is the liver, but it is also produced in a wide variety of tissues and has endocrine and paracrine modes of action. The mature IGF1 peptide has A, B, C, and D domains with homology to insulin, and is highly conserved.2 It is produced as an inactive precursor, pre-pro-IGF1, with an additional carboxyterminal E region that plays an important role in the maturation of normal IGF1 peptide. This regulatory region is obtained by alternative splicing of the last two exons. IGF1 resides on the long arm of chromosome 12 (12q 22–24.1),3 and several molecular studies have demonstrated that the structure of this gene is very complex. The gene contains six exons, which extend over more than 85 kb on chromosomal DNA. For human IGF1, two potential primary translation products exist: IGF1A and IGF1B, with sizes of 153 and 195 amino acids respectively. The two precursors are synthesised from distinct messenger RNAs produced by alternative splicing of the primary transcript. IGF1A mRNA contains exons 1, 2, 3, 4, and 6 of the human IGF1 gene while IGF1B is encoded by exons 1, 2, 3, 4, and 5. It has been speculated that IGF1B plays the major role during intrauterine growth, while the same function during postnatal growth is taken over by IGF1A.4

Recent studies have focused attention on the genetic causes of growth alterations. Mutations involving the molecular structure of GH5 or the function of …

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  • The first two authors contributed equally to this work.