title: Relationship between insulin-like growth factor-1 and radiographic disease in patients with primary osteoarthritis: a systematic review.
abstract: OBJECTIVE
  To evaluate the association between radiographic osteoarthritis (OA) and either serum insulin-like growth factor-1 (IGF-1) levels or IGF-1 gene polymorphisms in patients with primary OA.
  
  
  METHODS
  We conducted a systematic review of reported associations between circulating IGF-1 and/or IGF-1 gene polymorphisms and radiographic OA. Studies were eligible when: (1) investigating serum IGF-1 and/or IGF-1 gene polymorphisms in relation to prevalent or incident radiographic OA; (2) written in English; (3) full-text article or abstract; (4) patients had primary OA in knee, hip, hand or spine; (5) longitudinal, case-control or cross-sectional design. Quality assessment was done using a standardized criteria set. Best-evidence synthesis was performed based on guidelines on systematic review from the Cochrane Collaboration Back Review Group, using five evidence levels: strong, moderate, limited, conflicting and no evidence.
  
  
  RESULTS
  We included 11 studies with more than 3000 primary OA cases. Data on the relationship between serum IGF-1 and radiographic OA were inconsistent. Adjustment for body mass index (BMI) was often omitted. Of four high-quality studies, three studies reported no association, one study found significantly higher IGF-1 levels in OA patients compared to controls. Patients with IGF-1 gene promoter polymorphisms and a genetic variation at the IGF-1R locus had an increased OA prevalence compared to controls.
  
  
  CONCLUSIONS
  Observational data showed no association between serum IGF-1 and occurrence of radiographic OA (moderate level of evidence), and a positive relationship between IGF-1 gene polymorphisms and radiographic OA (moderate level of evidence); however the confounding effect of BMI was insufficiently addressed. Future well-designed prospective studies should further elaborate the role of the complex GH/IGF-1 system in primary OA.
authors.affiliation: Department of Endocrinology & Metabolic Diseases, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. K.M.J.A.Claessen@lumc.nl
authors.forename: K M J A
authors.initials: KM
authors.lastname: Claessen
authors.forename: S R
authors.initials: SR
authors.lastname: Ramautar
authors.forename: A M
authors.initials: AM
authors.lastname: Pereira
authors.forename: J W A
authors.initials: JW
authors.lastname: Smit
authors.forename: N R
authors.initials: NR
authors.lastname: Biermasz
authors.forename: M
authors.initials: M
authors.lastname: Kloppenburg
mesh_terms: D015415:Biomarkers / Q000097:blood; D019317:Evidence-Based Medicine / Q000379:methods; D020022:Genetic Predisposition to Disease; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D010003:Osteoarthritis / Q000097:blood* / Q000000981:diagnostic imaging / Q000235:genetics; D011110:Polymorphism, Genetic; D011859:Radiography
chemical_list: D015415:Biomarkers; D007334:Insulin-Like Growth Factor I