title: Insulin-like growth factor-I and insulin-like growth factor binding protein-3 serum levels in ankylosing spondylitis.
abstract: OBJECTIVE
  Low bone mass, vertebral osteopenia and fractures have been described in patients with ankylosing spondylitis (AS), but the aetiology of this osteoporosis (OP) remains unknown. Insulin-like growth factor-I (IGF-I), a bone-promoting peptide, may be considered as reflecting osteoblast function as well as its main binding protein, insulin-like growth factor binding protein-3 (IGFBP-3). Both were found to be decreased in post-menopausal women and male patients with idiopathic OP. In this study, we aimed to measure the circulating IGF-I and IGFBP-3 in AS patients.
  
  
  METHODS
  Thirty-three AS patients were compared to 23 healthy controls. Bone mineral density (dual X-ray absorptiometry) was measured at the spine and the femoral neck. We determined the serum levels of growth hormone (GH), insulin, glycaemia, and the IGF-I and IGFBP-3 serum concentrations.
  
  
  RESULTS
  A lowered lumbar spine bone mineral density was found in the AS group (AS: 0.946 g/cm2, controls: 1.02 g/cm2; P = 0.05). AS patients had a higher glycaemia than controls, but results were in the normal range. There were no significant differences in the mean values for GH and insulin. Mean IGF-I serum levels were 218.3 ng/ml (+/-72.4) in patients and 212.1 (+/-71.1) in controls (P = 0.75). The serum concentrations of IGFBP-3 were significantly lower in AS (3.29+/-0.6 microg/ml) than in healthy subjects (3.63+/-0.6 microg/ml; P = 0.05). There was a negative correlation between the serum IGFBP-3 concentration and erythrocyte sedimentation rate (r = -0.39; P = 0.025).
  
  
  CONCLUSIONS
  Since IGFBP-3 is an important cofactor for IGF-I and modulates its bioavailability and activity in bone, these data suggest that osteoblast cell function could be impaired in AS. Inflammation could play a role in this IGFBP-3/IGF-I axis involvement. However, further studies are warranted to determine the role of the other growth factors and their binding proteins in the OP of AS.
authors.affiliation: Department of Rheumatology, University Hospital J. Minjoz, Besançon, France.
authors.forename: E
authors.initials: E
authors.lastname: Toussirot
authors.forename: N U
authors.initials: NU
authors.lastname: Nguyen
authors.forename: G
authors.initials: G
authors.lastname: Dumoulin
authors.forename: J
authors.initials: J
authors.lastname: Regnard
authors.forename: D
authors.initials: D
authors.lastname: Wendling
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015519:Bone Density; D002118:Calcium / Q000097:blood; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D010006:Osteoblasts / Q000276:immunology; D010024:Osteoporosis / Q000209:etiology*; D010281:Parathyroid Hormone / Q000097:blood; D013167:Spondylitis, Ankylosing / Q000097:blood* / Q000150:complications
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D010281:Parathyroid Hormone; D007334:Insulin-Like Growth Factor I; D002118:Calcium