It's all about you. You have a personal banker, a personal trainer, perhaps even a personal acupuncturist who knows just which pressure points to jab. In a few years you may be able to add one more to the ever-growing list: your personal osteotherapist. As scientists gain new insights into the complex hormonal symphony sustaining the human skeleton, they're getting a clearer picture of why fractures are caused by the most common bone disease, osteoporosis. And they're coming up with more-individualized ways of treating and perhaps even curing the disease, which weakens bones by making them brittle and fragile.
Osteoporosis used to be considered a normal part of aging, characterized by a loss of height and, in women (the majority of patients), by the "dowager's hump" that makes you look bent over even when you're standing up. But researchers now understand that it's actually caused by an imbalance between two types of bone cells—osteoclasts, which break down old bone, and osteoblasts, which build up new bone. These two should operate together as part of the process that keeps your bones strong and healthy throughout your lifetime. When that balance is thrown off, osteoporosis results.
In the last 15 years, scientists have focused on drugs that slow bone loss; the most well known of these are part of a group called bisphosphonates, including Fosamax, Boniva and Actonel. But a new generation of drugs aims to build bone. These could work in concert with bisphosphonates or other medications that slow bone loss to re-create the balance necessary for the growth of healthy bone. Other researchers are looking at ways of using stem-cell technology to produce new bone. "It's very exciting," says bone researcher Clifford Rosen, senior staff scientist at the Maine Medical Center Research Institute. "It's a whole new paradigm of trying to get bone formed."
Treating osteoporosis is an urgent mission. This year alone, nearly 500,000 Americans will be admitted to the hospital because of osteoporosis-related fractures. Most of them probably didn't even know they were vulnerable because osteoporosis often causes no symptoms until that terrible moment when a hip or a wrist cracks. For older people, a bone injury can be fatal. According to the National Osteoporosis Foundation, 20 percent of older people who break a hip die within a year, and many of those who survive end up in a nursing home. But even for younger people, osteoporosis is seriously disabling. Over the last 20 years, scientists have identified groups who are at risk, including women over 65 and men over 70, younger women who weigh less than 127 pounds, heavy drinkers and smokers, and people who have taken certain medications such as steroids, antiseizure drugs and some breast-cancer therapies.
The process of breaking down and building up bone starts in childhood, when bone building dominates. By the time you reach your early 20s, the two are generally equal; this is when you achieve what scientists call peak bone mass—the most bone you will ever have. People who are physically active and get adequate calcium and vitamin D as children generally have higher peak bone mass, which puts them ahead as they get older and bone building slows down. In men, that slowdown happens gradually, but in women, the process is dramatically accelerated after menopause, when women lose estrogen, which helps protect against bone loss.
To help prevent injury, patients at risk should get their bone mass tested. A study published last week in The Journal of the American Medical Association gives doctors a new scoring system to predict the risk of hip fracture in postmenopausal women. Minor bone loss can be treated with calcium (for people over 50, the current recommendation is 1,200mg daily) and vitamin D (between 800 and 1,000 IU for older people). Weight-bearing exercise has also been shown to build bone, even in elderly people. But when those measures don't work, the next step could be medication. Bisphosphonates are currently the most widely used drugs to stop bone loss. The only drug approved so far by the FDA to promote bone growth is teriparitide, prescribed for people with severe osteoporosis, who cannot take the drug for more than two years. At this point, it is not widely used because it has to be administered by injection. Rosen thinks new ways of giving teriparitide and similar medications—perhaps in an inhaled form—would increase its popularity. He also sees a day when patients may use some combination of drugs that build bone and others that stop bone loss as a way of replicating the balance that exists in healthy bones.
Other scientists are looking at the nature of bone cells themselves in the hope that a better understanding of their structure and properties will help to eradicate osteoporosis. "We are really at the beginning of this kind of study," says Barbara Boyan, a professor of biomedical engineering at Georgia Tech and Emory. In her lab, Boyan and her colleagues have found intriguing sex differences in the transplantability of male and female cells. It's not clear yet what these differences mean, but Boyan thinks they might someday yield a more sophisticated explanation of why women are more vulnerable to osteoporosis (beyond the rapid decline of estrogen that occurs at menopause). "This is the era of personalized medicine," she says, and recognizing the importance of basic differences between the sexes should be the first step in individualizing treatment. Someday, those differences and others still undetected could make the dowager's hump disappear forever.