title: Serum insulin-like growth factor-I (IGF-I) does not correlate positively with isometric strength, fatigue, and quality of life in post-polio syndrome.
abstract: OBJECTIVE
  To determine if serum insulin-like growth factor-I (IGF-I) levels are associated with strength, body mass index (BMI), fatigue, or quality of life in post-poliomyelitis syndrome (PPS). PPS is likely due to a distal disintegration of enlarged post-polio motor units as a result of terminal axonal sprouting. Age-related decline in growth hormone and IGF-I (which support terminal axonal sprouts) is proposed as a contributing factor.
  
  
  METHODS
  As part of the North American Post-Poliomyelitis Pyridostigmine Study (NAPPS), baseline data on maximum voluntary isometric contraction (MVIC), BMI, subjective fatigue (fatigue severity scale, Hare fatigue symptom scale), health-related quality of life (short form health survey-36; SF-36), and serum IGF-I levels were gathered on 112 PPS patients. Pearson correlation coefficients were calculated to evaluate the association between serum IGF-I and MVIC in 12 muscles, BMI, two fatigue scales, and SF-36 scale scores.
  
  
  RESULTS
  There is a significant inverse correlation of IGF-I levels with MVIC in left ankle dorsiflexors (r=-0.30, P<0.01), and left and right knee extensors (r=-0.22, -0.25, P=<0.01, 0.01), but no significant correlations in other muscles. When men and women were evaluated separately, inverse correlations of IGF-I levels with MVIC were found only in men. IGF-I correlated inversely with BMI (r=-0.32, P=0006) and age (r=-0.32, P=0.0005). IGF-I did not correlate with the fatigue or SF-36 scales.
  
  
  CONCLUSIONS
  In this exploratory study, we found that contrary to our expectations, IGF-I did not correlate positively with strength. IGF-I correlated negatively with strength in several lower extremity muscles, BMI, and age. IGF-I is likely not an important factor in the pathogenesis of fatigue and in determining quality of life in PPS, but its role on strength should be studied further.
authors.affiliation: Department of Neurology, Montreal Neurological Hospital, McGill University Health Centre and Montreal Neurological Institute, McGill University, Quebec, H3A 2B4, Montreal, Canada.
authors.forename: D A
authors.initials: DA
authors.lastname: Trojan
authors.forename: J
authors.initials: J
authors.lastname: Collet
authors.forename: M N
authors.initials: MN
authors.lastname: Pollak
authors.forename: S
authors.initials: S
authors.lastname: Shapiro
authors.forename: B
authors.initials: B
authors.lastname: Jubelt
authors.forename: R G
authors.initials: RG
authors.lastname: Miller
authors.forename: J C
authors.initials: JC
authors.lastname: Agre
authors.forename: T L
authors.initials: TL
authors.lastname: Munsat
authors.forename: D
authors.initials: D
authors.lastname: Hollander
authors.forename: R
authors.initials: R
authors.lastname: Tandan
authors.forename: A
authors.initials: A
authors.lastname: Robinson
authors.forename: L
authors.initials: L
authors.lastname: Finch
authors.forename: T
authors.initials: T
authors.lastname: Ducruet
authors.forename: N R
authors.initials: NR
authors.lastname: Cashman
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D009132:Muscles / Q000503:physiopathology; D016262:Postpoliomyelitis Syndrome / Q000097:blood* / Q000503:physiopathology*; D011788:Quality of Life; D012737:Sex Factors; D011795:Surveys and Questionnaires
chemical_list: D007334:Insulin-Like Growth Factor I