title: Serum insulin-like growth factor 1 in the aging horse.
abstract: BACKGROUND
  Insulin-like growth factor 1 (IGF-1) has important roles in anabolic processes in the musculoskeletal system and has been reported to decrease with age in both people and horses.
  
  
  OBJECTIVE
  The objective of this study was to determine serum IGF-1 levels in the aging horse from early to late adulthood (age range 5-27 years).
  
  
  METHODS
  Healthy horses (n = 72) were used in a cross-sectional study, while 37 paired serum samples were available for a longitudinal study. Serum IGF-1 protein was determined using an ELISA kit validated for use in equine samples.
  
  
  RESULTS
  No association was found between serum IGF-1 levels and age in the cross-sectional study. In the longitudinal study, a latent variable model fitted to the data revealed that horses in general experienced a 5.2% increase of serum IGF-1 levels over a 5-year period, but horses crossing a change point around 9 years of age between the 2 samples experienced an 11.0% decrease.
  
  
  CONCLUSIONS
  In this study, there was no evidence for aging being a factor in changes of IGF-1 levels in an adult and old horse population.
authors.affiliation: Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Tone
authors.initials: T
authors.lastname: Lygren
authors.forename: Sanni
authors.initials: S
authors.lastname: Hansen
authors.forename: Henning
authors.initials: H
authors.lastname: Langberg
authors.forename: Julie
authors.initials: J
authors.lastname: Fjeldborg
authors.forename: Stine
authors.initials: S
authors.lastname: Jacobsen
authors.forename: Mette O
authors.initials: MO
authors.lastname: Nielsen
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.forename: Bo
authors.initials: B
authors.lastname: Markussen
authors.forename: Preben D
authors.initials: PD
authors.lastname: Thomsen
authors.forename: Lise C
authors.initials: LC
authors.lastname: Berg
mesh_terms: D000375:Aging / Q000097:blood; D000818:Animals; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D006736:Horses / Q000097:blood* / Q000254:growth & development; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008137:Longitudinal Studies; D008297:Male
chemical_list: D007334:Insulin-Like Growth Factor I
keywords: ELISA; equine; growth factors; longitudinal study; senescence