Serum insulin-like growth factor binding protein-2 levels as an indicator of functional ability in elderly men.
BACKGROUND
In a cross-sectional study in 403 healthy, independently living elderly men (mean age 78 years), we determined which are the main physiological determinants of functional ability in the elderly, and which components of the somatotropic system contribute to the maintenance of functional ability.


METHODS
Functional ability was assessed by the number of problems in activities of daily living and by a measure of physical performance. Other physical characteristics included leg extensor strength, bone mineral density of total body and proximal femur, and body composition, including lean mass and fat mass. Serum insulin-like growth factor (IGF)-I and its binding proteins (IGFBP) -1, -2 and -3 concentrations were all measured by RIA.


RESULTS
Muscle strength was related to a lower degree of disability. Further, it was positively related to physical performance and bone mineral density (all P<0.001). Fat mass influenced activities of daily living and physical performance negatively and bone mineral density positively (all P<0.001). Serum concentrations of IGF-I and IGFBP-3 were not related to any of the physical characteristics. High serum IGFBP-2 concentrations were related to a higher degree of disability (P<0.001), a lower physical performance (P=0.006), muscle strength (P=0.002), bone mineral density of proximal femur (P=0.007), lean mass and fat mass (both P<0.001). Serum insulin and IGFBP-1 concentrations were independently, positively related to lean mass (P=0.003) and fat mass (P<0.001).


CONCLUSIONS
In independently living elderly men, functional ability appears to be determined by muscle strength (positive) and fat mass (negative). Low serum IGFBP-2 concentrations are a powerful indicator for overall good physical functional status, probably inversely reflecting the integrated sum of nutrition and the biological effects of growth hormone, IGF-I and insulin.
van den Beld
Annewieke W
AW
Department of Internal Medicine III, Room D4, Erasmus University Medical Center, 40 Dr. Molewaterplein, 3015 GD Rotterdam, The Netherlands. a.vandenbeld@erasmusmc.nl
Blum
Werner F
WF
Pols
Huibert A P
HA
Grobbee
Diederick E
DE
Lamberts
Steven W J
SW
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D015415:Biomarkers; D015992:Body Mass Index; D015519:Bone Density; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction; D011237:Predictive Value of Tests; D011467:Prostate / Q000473:pathology
D015415:Biomarkers; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I