Diminished bone density is common among menopausal women and raises their risk of osteoporosis, bone fractures and subsequent complications. Research has traditionally focused on therapies that seek to maintain the level of estrogen in the body. This hormone seems to sustain bone health, but it drops to an extremely low level during and after menopause.
However, research conducted by a team at the Medical College of Georgia in Augusta, GA suggests that another hormone, follicle-stimulating hormone (FSH) may also be involved in decreasing bone mineral density during menopause. Dr. Joseph Cannon, Kellett Chair in Allied Health Sciences, will present his team's research at the American Physiological Society's Experimental Biology 2010 conference in Anaheim on April 24-28, 2010.
Increasing FSH Correlates to Decreasing Bone Density
The level of FSH gradually increases in the five years leading up to menopause, when it reaches its peak and estradiol bottoms out. Research has indicated that bone density begins to decrease over the same period of time. Also, data from animal studies indicated a link between FSH and bone density. This led Cannon and his colleagues to probe whether the increase of FSH has an effect on bone density in humans.
Bone mineral density is a balancing act between bone loss and bone growth involving two types of cells in the body: osteoclasts that break down bone, and osteoblasts that regenerate it. During menopausal bone loss, the osteoclasts' destructive activity outweighs the osteoblasts' rebuilding activity, resulting in an overall weakening of the bone.
Cytokines, which are secreted by white blood cells such as monocytes, are thought to play a role in this imbalance. One cytokine in particular, interleukin-1 beta (IL-1), is known to activate osteoclasts. "Our hypothesis was that [FSH] was decreasing bone mineral density by influencing the production or action of cytokines," said Dr. Cannon.
Data in Cells Confirms Hormone's Effect in Women
To test their hypothesis, the researchers conducted a study of 36 women from 20 to 50 years old. By measuring each woman's level of FSH and then using a low-energy x-ray to analyze her bone density, the researchers saw that higher levels of FSH among the women were indeed associated with lower bone density.
These results prompted Cannon and his team to determine the effects of FSH on a cellular level. They collected blood samples from the study participants and isolated the monocytes to investigate the effect of FSH on cells outside of the body.