title: Serum insulin-like growth factor-I in diabetic retinopathy.
abstract: OBJECTIVE
  To assess the relationship between serum insulin-like growth factor I (IGF-I) and diabetic retinopathy.
  
  
  METHODS
  This was a clinic-based cross-sectional study conducted at the Emory Eye Center. A total of 225 subjects were classified into four groups, based on diabetes status and retinopathy findings: no diabetes mellitus (no DM; n=99), diabetes with no background diabetic retinopathy (no BDR; n=42), nonproliferative diabetic retinopathy (NPDR; n=41), and proliferative diabetic retinopathy (PDR; n=43). Key exclusion criteria included type 1 diabetes and disorders that affect serum IGF-I levels, such as acromegaly. Subjects underwent dilated fundoscopic examination and were tested for hemoglobin A1c, serum creatinine, and serum IGF-I, between December 2009 and March 2010. Serum IGF-I levels were measured using an immunoassay that was calibrated against an international standard.
  
  
  RESULTS
  Between the groups, there were no statistical differences with regards to age, race, or sex. Overall, diabetic subjects had similar serum IGF-I concentrations compared to nondiabetic subjects (117.6 µg/l versus 122.0 µg/l; p=0.497). There was no significant difference between serum IGF-I levels among the study groups (no DM=122.0 µg/l, no BDR=115.4 µg/l, NPDR=118.3 µg/l, PDR=119.1 µg/l; p=0.897). Among the diabetic groups, the mean IGF-I concentration was similar between insulin-dependent and non-insulin-dependent subjects (116.8 µg/l versus 118.2 µg/l; p=0.876). The univariate analysis of the IGF-I levels demonstrated statistical significance in regard to age (p=0.002, r=-0.20), body mass index (p=0.008, r=-0.18), and race (p=0.040).
  
  
  CONCLUSIONS
  There was no association between serum IGF-I concentrations and diabetic retinopathy in this large cross-sectional study.
authors.affiliation: Department of Vitreoretinal Surgery and Disease, Emory University, Atlanta, GA, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Payne
authors.forename: Vin
authors.initials: V
authors.lastname: Tangpricha
authors.forename: Julia
authors.initials: J
authors.lastname: Cleveland
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lynn
authors.forename: Robin
authors.initials: R
authors.lastname: Ray
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Srivastava
mesh_terms: D000368:Aged; D015992:Body Mass Index; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D003930:Diabetic Retinopathy / Q000097:blood*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007118:Immunoassay; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D014481:United States
chemical_list: D003404:Creatinine; D006442:Glycated Hemoglobin; D007334:Insulin-Like Growth Factor I