Serum insulin-like growth factor-I (IGF-I) does not correlate positively with isometric strength, fatigue, and quality of life in post-polio syndrome.
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.
Trojan
D A
DA
Department of Neurology, Montreal Neurological Hospital, McGill University Health Centre and Montreal Neurological Institute, McGill University, Quebec, H3A 2B4, Montreal, Canada.
Collet
J
J
Pollak
M N
MN
Shapiro
S
S
Jubelt
B
B
Miller
R G
RG
Agre
J C
JC
Munsat
T L
TL
Hollander
D
D
Tandan
R
R
Robinson
A
A
Finch
L
L
Ducruet
T
T
Cashman
N R
NR
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
D007334:Insulin-Like Growth Factor I