Relationship between baseline insulin-like growth factor-I (IGF-I) and femoral bone density in women aged over 70 years: potential implications for the prevention of age-related bone loss.
OBJECTIVE
To test the hypothesis that the decline in femoral bone mass associated with healthy aging is partially accounted for by deficiency of the growth hormone-insulin-like growth factor-I (IGF-I) axis.


METHODS
Cross-sectional study.


METHODS
A sample of 245 community-dwelling healthy women aged 70 and older. Exclusion criteria were diseases or medications known to affect the musculoskeletal system or the somatotrophic axis.


METHODS
Serum levels of IGF-I, calcitriol, and osteocalcin were determined by radioimmunoassay; serum calcidiol was measured by competitive binding assay, and serum parathyroid hormone (PTH) was assessed immunochemically. Urinary pyridinium crosslinks were measured by fluorescent detection after high-pressure liquid chromatography. Isometric and isokinetic quadriceps strength was evaluated using an isokinetic dynamometer. Bone density (BMD) was assessed by dual-energy X-ray absorptiometry at the proximal femur. Multiple regression was used to adjust for potential confounders.


RESULTS
At the proximal femur, BMD declined by 0.59-0.84% per year. In addition to body mass index and muscle strength, serum IGF-I was found to be an independent predictor of BMD at all femoral sites.


CONCLUSIONS
The data support the hypothesis that circulating IGF-I not only reflects the integrated growth hormone secretion but also has a direct role in the endocrine regulation of bone remodeling. The present findings support the need for further studies to assess the potential of IGF-I in attenuating age-related femoral bone loss.
Department of Internal Medicine, Katholicke Universiteit Leuven, Belgium.
S
S
Boonen
E
E
Lesaffre
J
J
Dequeker
J
J
Aerssens
J
J
Nijs
W
W
Pelemans
R
R
Bouillon
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism* / Q000473:pathology*; D015519:Bone Density; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D005260:Female; D005269:Femur / Q000473:pathology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D015663:Osteoporosis, Postmenopausal / Q000175:diagnosis / Q000378:metabolism; D011237:Predictive Value of Tests; D012044:Regression Analysis
D007334:Insulin-Like Growth Factor I