Osteoperosis

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BONE INTEGRITY IN OLDER WOMEN LINKED TO IGF-1 LEVELS

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- EVIDENCE OF A STRONG HORMONE CONNECTION

As women age, osteoporosis increasingly becomes a major health threat.

The result of ignoring its subtle and gradual physiological damage can

include not only future pain and discomfort, but hospitalization, loss

of independence, and even death.

To tease out some of the possible synergistic hormonal mechanisms

involved in progressive bone loss, researchers from the National

Institute of Health and other organizations studying health and aging

examined the association between bone density and the human growth

factor IGF-1. This large-scale cross-sectional study, the Framingham

Osteoporosis Study, examined over 650 elderly men and women between the

ages of 72 and 94 who participated in the Framingham Heart Study.

The researchers found a significant positive correlation between IGF-1

levels and bone density in women in all five sites analyzed: Ward's

area, femoral neck, radius, trochanter, and lumbar spine. This

relationship remained intact even after adjusting for possible

confounding factors such as protein intake, body mass, estrogen levels,

and smoking. A similar association was not established in men, however,

and researchers speculated that this may be related to differences in

sex hormones.

" IGF-1 has been reported to decline during and after menopause,

suggesting an interrelationship between IGF-concentrations, estrogen

levels, and bone loss in postmenopausal women, " they noted. " Although

IGF-1 levels decline with estrogen, maintenance of relatively high

levels of IGF-1 in postmenopause in some women may explain in part their

higher bone mineral density. "

IGF-1 has been shown to spur bone growth formation. Levels are affected

by nutrition and health status, including protein intake. More long-term

clinical studies are needed, the researchers suggest, to gauge the

safety and effectiveness of using growth hormone therapy to boost the

body's supply of IGF-1 in women who need to take additional measures to

protect against bone loss.

Source: Langlois JA, Clifford CJ, Visser M, Hannan MT, T,

PWF, and Kiel DP. Association between insulin-like growth factor I and

bone mineral density in older women and men: the Framingham Heart Study.

J Clin Endocrinol Metab 1998;83(12):4257-4262.