Health

While it's true that all people lose bone as they age, osteoporosis is not inevitable. There's a lot you can do to shield your bones from this disease.

Ideally, prevention begins in childhood and continues throughout your life. The best insurance against osteoporosis is to reach the highest bone density possible by your 30s and to minimize bone loss after that. But even if you weren't aware of the importance of building bone during your teen years and you're already in midlife or beyond, there are still many things you can do to hold on to the bone you have and perhaps even to replace lost bone.

The foundation for prevention and treatment is simple: Get enough calcium and vitamin D, engage in weight-bearing exercise regularly, and take appropriate medications when necessary. You can also protect your bones by avoiding bone-depleting habits such as smoking and excessive alcohol use.

Calcium

If you don't supply your body with the calcium it needs, it will respond by raiding calcium stores in your bones, weakening them. Consuming adequate amounts of calcium limits these unhealthy withdrawals and safeguards your bones. Calcium alone can't protect you from bone losses caused by certain medications or diseases, a sedentary lifestyle, smoking, alcoholism, or a lack of estrogen. But getting enough calcium plays an essential role in the health and strength of your bones.

Most people already know this, but that knowledge doesn't always translate into action. Only 45% of adult men and 22% of adult women get the recommended amount of calcium, and the numbers are even worse for youngsters. Among 9- to 17-year-olds, just 25% of boys and 10% of girls get enough calcium.

Since your body's calcium demands shift with age, you should adjust your calcium intake as necessary. How much calcium is enough? That question is at the center of a vigorous debate. The National Academy of Sciences has established recommended intakes by age (see Table 1). These guidelines are supported by the National Institutes of Health and the National Osteoporosis Foundation. However, some experts believe that the recommendations may be too high, particularly for men.

A report from the Harvard School of Public Health points out that the average daily calcium intake in countries such as India and Japan is as low as 300 milligrams (mg), and that fracture rates are low. But it goes on to say that the low fracture rates may be the result of differences in other bone health factors, such as the amount of exercise or exposure to sunlight (which spurs production of vitamin D). Critics of the current calcium recommendations also say that there's little evidence that high intake has more than a marginal effect on bone density and fracture prevention. And they cite Harvard studies of male health professionals and female nurses that found that the participants who drank one glass of milk or less a week weren't any more likely to break a hip or forearm than those who drank more milk.

What's the drawback of getting high amounts of calcium? For women, there doesn't seem to be any disadvantage to getting 1,000–1,300 mg of calcium a day. The story may be different for men, though. Some studies have found a connection between calcium and prostate cancer. The Health Professionals Follow-up Study found that men who drank two or more glasses of milk a day were almost twice as likely to develop advanced prostate cancer as those who didn't drink milk at all. At first, researchers thought the connection was due to the saturated fat in dairy products. But the results from this study, as well as more careful analyses of other data, suggest that calcium is the culprit. Great Britain set its daily calcium recommendation at 700 mg, which Harvard researcher and professor Walter Willett believes is probably closer to the amount that men should be consuming.

But proponents of the current calcium recommendations say that dozens of studies have shown that high calcium intake builds bone and prevents fractures. According to a report from the National Institutes of Health, randomized clinical trials have found that adequate calcium intake — from either diet or supplements — increases bone mineral density in the spine and reduces vertebral and other fractures. One study found that calcium supplements lowered the risk for fracture by 25%–70% in women who had already gone through menopause.

Another study of 389 men and women ages 65 or older found that the participants who took 500 mg of calcium and 700 IU (International Units) of vitamin D daily lost significantly less bone over the course of three years than their counterparts who did not receive additional calcium and vitamin D. In some cases, men taking the combination actually increased their bone density. In addition, the group taking supplements had fewer nonvertebral fractures. This is in keeping with a study of 3,000 elderly French women in nursing homes, which found that among women taking 1,200 mg of calcium and 800 IU of vitamin D, hip fractures dropped by 43% and nonvertebral fractures decreased by 32%.

Calcium may also boost the power of osteoporosis treatments, such as hormone therapy. An analysis of studies of women on hormone therapy found that bone mineral density was significantly greater in those who got nearly 1,200 mg of calcium a day as compared with those who got about 600 mg a day.

Proponents of the higher calcium recommendations also cite calcium's other possible benefits, such as modest protection against colon cancer.

More information on the relationship between calcium and fractures is on the way, and it may help settle this debate. As part of the ongoing Women's Health Initiative, nearly 40,000 women are participating in a study comparing the effect of calcium and vitamin D supplements against that of a placebo. Results, which are due in 2005–2006, should shed more light on the matter.

In the meantime, calcium continues to be an important tool in the fight against osteoporosis. While scientists debate the optimal amount and sources of calcium (see "Sources of Calcium"), it's clear that calcium plays a crucial role in bone health and that you should not neglect it in your diet.

Vitamin D

Vitamin D is essential to bone health. It plays a vital role in calcium absorption by allowing calcium to travel out of the intestines and into the bloodstream. A 2003 study found that vitamin D supplementation increased calcium absorption by 65%.

Other studies uncovered a relationship between low levels of vitamin D and low bone density, and there is some evidence that older women who don't get enough of this vitamin are at greater risk for hip fracture. A 2002 meta-analysis published in Endocrine Reviews also found that vitamin D supplements may reduce the risk for spine fractures by 37%. Why the decrease in fractures? The Surgeon General's report on osteoporosis speculated that vitamin D may actually reduce a person's risk of falling by activating receptors on muscles that play a role in increasing muscle strength and stability.

Vitamin D and sunlight While your body produces vitamin D from sunlight, most people need a supplement to get the recommended amount of this vitamin.

Current vitamin D recommendations are 200 IU for people ages 1–50, 400 IU for people ages 51–70, and 600 IU for people ages 71 and older. However, there is some evidence that we need more vitamin D than the currently recommended levels. With this in mind, some experts suggest getting as much as 800–1,000 IU of vitamin D per day.

If you don't get an adequate amount of vitamin D, your body won't be able to absorb enough calcium from the foods you eat and instead will rely on the calcium in your bones. That's the case for many adults. One survey published in the June 2004 Journal of the American Dietetic Association found that two in three Americans between ages 51 and 70 fall short of the current target for vitamin D. The situation is even worse for older people, with 9 in 10 not getting enough of the vitamin.

Vitamin D is made in the skin after exposure to sunlight. Some people make all the vitamin D they need by going outside for a few minutes a day without sunscreen. You should keep your exposure time short — just 10 to 15 minutes a day — to protect against skin cancer. However, you may find that sunlight alone won't generate adequate amounts of vitamin D. For example, if you live above 40 degrees latitude (the latitude of Denver, Indianapolis, and Philadelphia), the winter sunlight isn't strong enough to enable you to produce significant amounts of vitamin D. Sunscreen, glass, and clothing also interfere with this process, diminishing your ability to produce the vitamin. And as you age, your skin can't produce vitamin D as readily, and your intestines have more difficulty absorbing this vitamin.

Limit caffeine, protein, and vitamin A In high amounts, some substances — such as caffeine, protein, and vitamin A — can harm your bones, so it's wise to keep a watchful eye on just how much of these you're getting. Some preliminary research suggests that drinking four or more cups of coffee a day can put you at greater risk of breaking a bone. It seems that high levels of caffeine may increase calcium excretion in the kidneys. More study is needed, but in the meantime you may want to forgo that fourth cup. High levels of protein, particularly protein from animal sources, may also cause calcium to leach from your bones. Experts haven't pinpointed a cutoff amount, but they suggest that you keep an eye on the amount of animal protein you get. Several studies have found a link between high vitamin A intake and fractures. A 2002 study in the Journal of the American Medical Association found that postmenopausal women who got more than 3,000 mcg of vitamin A were more likely to break a hip. And a 2003 study in the New England Journal of Medicine found that men with the highest amounts of vitamin A in their blood were also at greatest risk of breaking a bone. Currently, the recommended daily amount of vitamin A is 700 mcg (about 2,300 IU) for women and 900 mcg (about 3,000 IU) for men. You can get vitamin A through the nutrient beta carotene or as preformed vitamin A. Beta carotene has not been linked to hip fractures. Thus, it's safer to get your vitamin A in this form. If you take a multivitamin that contains vitamin A, check to make sure that a significant part of its vitamin A comes from beta carotene. Also, avoid taking high-potency vitamin A supplements. Limit caffeine, protein, and vitamin A Keeping your coffee intake to three cups or less a day may benefit your bones.

You can try to make up for the shortage with your diet, but only a few foods — such as eggs, saltwater fish, and liver — contain vitamin D. In the United States, milk is fortified with this vitamin; an 8-ounce glass should have about 100 IU. Ultimately, taking one daily multivitamin may be the easiest way to ensure that you get enough vitamin D. Most multivitamins contain 400 IU.

Because too much of this vitamin can be dangerous, keep your daily intake below 2,000 IU. In general, you'll get far less than that from food, sunlight, and a multivitamin, but if you're taking several different vitamin pills, it's important to review your daily dose.

Exercise

Weight-bearing exercise is also important. Not only does it help increase your peak bone mass, but it also aids in maintaining bone strength. Our skeletons aren't choosy; any exercise that involves working against gravity, such as running, walking, playing soccer, weightlifting, or stair-climbing, can potentially build bone. Because activities like swimming and bicycling aren't weight-bearing, they don't help strengthen bones. Generally, among weight-bearing activities, higher-impact exercises such as weightlifting have a more pronounced effect on bone than lower-impact exercises such as walking. Aim to get at least 30 minutes of weight-bearing exercise a day.

Exercise offers other benefits. It increases muscle mass, which can help protect bones from injury. It also improves strength, agility, and flexibility, thus decreasing susceptibility to falls. Some studies have found that exercise can cut the risk of falling by 25%. Additionally, findings from the Nurses' Health Study published in the Journal of the American Medical Association in 2002 revealed that walking at least four hours a week appeared to lower the risk for hip fracture by 41%.

It's apparent that exercise during childhood and adolescence can produce significant increases in bone mineral density. However, it also seems clear that exercise among the most vulnerable of the elderly can have dramatic effects: doubling their strength and muscle mass. In other words, it's never too late to start an exercise program (see "The importance of exercise").

For women and men who are at greater risk for osteoporosis or who have already been diagnosed with the condition, exercise and a diet rich in calcium and vitamin D alone won't provide sufficient bone protection. These people may need to add medication.

The bisphosphonates

The bisphosphonates are a family of drugs used to prevent or treat osteoporosis in postmenopausal women. They are also used to treat men in certain cases. These medications are often the first choice of doctors and patients alike. This is because they reduce hip, wrist, and spinal fractures, and when they are taken properly they have few side effects. These attributes have made bisphosphonates an attractive alternative to hormone therapy, which was once widely used for stemming bone loss but has fallen out of favor (see "Hormone therapy"). The bisphosphonates typically prescribed for osteoporosis are alendronate (Fosamax) and risedronate (Actonel). The FDA has also approved a newer medication called ibandronate (Boniva) for use in treating osteoporosis, but this drug isn't yet available as of the printing of this publication (see "Ibandronate").

Like most of the medications approved for treating osteoporosis, bisphosphonates are antiresorptive, meaning that they reduce bone resorption or turnover. They slow bone loss and produce modest increases in bone density. Specifically, the bisphosphonates bind themselves to hydroxyapatite (the cement-like substance in bones) and interfere with bone-depleting osteoclasts, narrowing the gap between osteoclast activity and osteoblast activity. As a result, osteoblasts (which build bone) have an opportunity to fill in more of the tunnels left by osteoclasts.

The bisphosphonates don't seem to interact with other medications and are usually well tolerated. They can be hard to digest and may cause nausea, heartburn, or irritation of the stomach or esophagus, but these problems can be alleviated if the medications are taken properly (see "How to take alendronate and risedronate"). Another advantage to these medications is that they are available in weekly as well as daily dosages; taking weekly doses may further reduce side effects.

How to take alendronate and risedronate Since both alendronate and risedronate can be difficult to digest, people taking these medications must follow instructions carefully to avoid unpleasant side effects such as heartburn, nausea, or difficulty in swallowing. (Although ibandronate is currently not on the market, it too should be taken in a similar manner.) The first thing in the morning, take either medication on an empty stomach with a large glass of water and then remain upright for at least 30 minutes. During this time, avoid eating, drinking, or taking another medication. It's important to take the medication with water, rather than coffee or orange juice, both of which can interfere with your body's ability to absorb and use the drug. Most people tolerate these medications well, when they take the pills as instructed. In fact, side effects are uncommon among people taking alendronate and risedronate in clinical studies. Perhaps these study participants are more likely to take their medications exactly as directed. The consequences of not taking alendronate properly became evident a few months after it was on the market. In March 1996, the manufacturer, Merck Pharmaceutical Company, notified physicians that the incidence of esophagitis, ulcers, and other gastrointestinal side effects among women taking the drug was higher than it had been during clinical trials. The company attributed these side effects to patients failing to drink enough water with the pills or returning to bed after taking the medication. Alendronate and risedronate thus may not be the best choice for those who have difficulty swallowing, recurrent heartburn, acid reflux, esophagitis, or stomach ulcers. How to take alendronate and risedronate It's important to take bisphosphonates with a large glass of water.

Alendronate (Fosamax)

Alendronate is commonly used to prevent or treat osteoporosis in postmenopausal women. In September 2000, alendronate became the first medication approved for treating men with osteoporosis. It is also approved to treat glucocorticoid-induced osteoporosis in both men and women.

Since 1995, when alendronate received its initial FDA approval, studies have consistently shown that it can slow or even halt bone loss, increase bone density, and reduce the risk for spinal and hip fractures. In the Fracture Intervention Trial, 2,028 women ages 55–81 who already had osteoporosis were randomly assigned to take either alendronate or a placebo. Over the three-year period, women who were taking alendronate had 47% fewer vertebral fractures and 51% fewer hip fractures than did those in the placebo group. And a multicenter study of women with osteoporosis found that the women taking alendronate had higher bone mineral density — 8.8% higher in the spine, 5.9% higher in the thighbone, and 2.5% higher in the total body — than women who weren't taking any medication.

Alendronate is also effective as a preventive medication. The Early Postmenopausal Intervention Cohort study, involving 1,600 women ages 45–59, found that women taking alendronate increased their bone mass by 3.46% in the spine and 1.8% in the hip. These increases closely matched those of women on hormone therapy, whose bone mass increased 4% at the spine and 1.83% at the hip. But alendronate does not have hormone therapy's other effects — either good or bad. While it won't alleviate menopausal symptoms, it also doesn't affect the risk for heart disease or breast cancer. That's because it is a highly specific drug. It travels preferentially to spots where bone turnover is high, such as the hips and spine. There it halts osteoclasts (the cells that break down bone) in their tracks and stalls bone resorption.

According to the Surgeon General's report on bone loss, studies indicate that alendronate seems to be safe and effective for up to 10 years and that it yields results quickly. A follow-up of the Fracture Intervention Trial found that alendronate was able to reduce the risk for spinal fractures within a year, and evidence of a reduced risk for hip fractures was seen at 18 months. The same study found that the medication worked well for most of the women taking it: 95% of the postmenopausal women using this medication maintained or increased their bone mass. In addition, the benefits of this medication seem to linger even after people stop using it. A study published in the Journal of Clinical Endocrinology and Metabolism in 2000 found that the bone mineral density of women who had taken alendronate for several years was maintained for two years after they stopped taking the drug.

Risedronate (Actonel)

Risedronate, like its cousin alendronate, is used to prevent and treat osteoporosis in postmenopausal women, and it may be used to prevent or treat glucocorticoid-related osteoporosis in men and women.

Also like alendronate, risedronate has been shown to impede bone loss, increase bone mineral density, and reduce the risk for fractures. According to the Surgeon General's report on bone health, studies of postmenopausal women have found that risedronate can increase bone mineral density in the spine by 5% and in the hip by 2%–3% after three years of use. Studies have also found that risedronate can cut the risk for spine fractures by 41% and hip fractures by 30%.

Like alendronate, risedronate works relatively quickly. A study published in 1999 in the Journal of the American Medical Association found that the medication could lower the risk for spine fractures after one year. In addition, risedronate seems to have few side effects, particularly when it is taken properly (see "How to take alendronate and risedronate"). According to the Surgeon General's report on bone health, studies have examined the safety of risedronate for up to five years and have found it to be safe and effective.

Ibandronate (Boniva)

This bisphosphonate has received FDA approval for preventing and treating osteoporosis. While the makers of the drug received approval for a once-a-day tablet, they don't plan to sell that product to consumers. Instead, they are focusing their efforts on a once-a-month version of ibandronate (see "Is a once-a-month or once-a-year treatment on the way?"). The two drug companies collaborating on this project, Roche Pharmaceuticals and GlaxoSmithKline, have already developed a tablet that is taken just once a month. At the time this report went to press, the once-a-month pill was still being tested and had not received FDA approval yet.

Like the other bisphosphonates approved for treating osteoporosis, ibandronate increases bone mineral density and helps prevent fractures. A study published in the Journal of Bone Mineral Research in July 2004 found that the medication cut vertebral fractures by half. The study, which included more than 2,900 women ages 55–80, also found that the women who took ibandronate every day increased their bone mass by 6.5% in the spine and 3.4% in the hip.

The side effects of ibandronate are similar to those of alendronate and risedronate. It can cause heartburn, ulcers, irritation of the esophagus, and difficulty with swallowing.

Raloxifene (Evista)

Raloxifene is one of a class of drugs known as selective estrogen receptor modulators (SERMs). SERMs such as tamoxifen and raloxifene, which are often called "designer estrogens," have generated a great deal of interest due to their ability to mimic some of estrogen's positive effects without some of the negative consequences (see "Hormone therapy"). Like estrogen, raloxifene slows bone loss, but it does not increase the risk for uterine cancer and it seems to protect against breast cancer.

SERMs work by traveling to target cells where they attach to estrogen receptors, in the way a key would fit a lock. If there is a good fit between a hormone and receptor, the connection stimulates a response in the cells — for example, encouraging the growth of endometrial tissue or certain kinds of cancerous tumors. But if the fit isn't precise, no activity is sparked. By bonding to a receptor without stimulating it, the SERMs essentially block out estrogen, keeping it from attaching to the receptor and triggering a reaction. In this manner, SERMs can inhibit tumor growth. SERMs also seem to lower the levels of LDL cholesterol (commonly referred to as "bad" cholesterol). Side effects are rare, but do include hot flashes and deep vein thrombosis, a condition causing blood clots in deep veins, most commonly in the legs.

Raloxifene, which is used to prevent or treat osteoporosis in women, slows bone loss and offers modest increases in bone density. In clinical studies, it has reduced spinal fractures by 30% to 50%.

It has other positive effects, too. In a study of 7,705 postmenopausal women who had osteoporosis, known as the Multiple Outcomes of Raloxifene Evaluation (MORE), raloxifene reduced the risk for breast cancer by 76%. The results were even more impressive for a particular type of cancer, estrogen receptor–positive breast cancer, which is the most common form of breast cancer among older women. Some doctors are beginning to prescribe raloxifene as a preventive medication for breast cancer.

Hormone therapy

Hormone therapy is the oldest treatment for osteoporosis. Once it was the most widely prescribed, but its use has fallen sharply as negative effects of the therapy have come to light.

In years past, the conventional wisdom on hormone therapy was that, in addition to easing menopausal symptoms and improving bone strength, it could help protect against heart disease. The glow of hormone therapy was dimmed by speculation that it might slightly increase the risk of developing breast cancer, but this remained a source of debate. But evidence of the negative effects of hormone therapy has mounted. A number of studies have documented a link between hormone therapy and breast cancer, and the once widely held belief that hormone therapy protected against heart disease has been turned on its head. Instead, hormone therapy appears to increase the risk for heart attack, as well as increase the number of strokes and blood clots in the legs and lungs.

Now, most doctors no longer recommend hormone therapy for treating bone loss; instead, it is primarily used as a short-term treatment for troublesome menopausal symptoms such as hot flashes. Interestingly, the study that led more doctors and patients to turn away from hormone therapy is the same one that demonstrated that hormone therapy reduces fractures.

Hormone therapy: A brief history

Estrogen was the first drug to be approved by the FDA for the treatment of osteoporosis. In the 1970s, many women were taking estrogen in the menopausal years to relieve symptoms like hot flashes and vaginal dryness. In the 1980s, when research showed that women taking estrogen alone were at increased risk for endometrial cancer, doctors added progestins (synthetic versions of the hormone progesterone) as a preventive measure. While estrogen encourages the growth of the tissue lining the uterus, progestin curbs it. Estrogen-progestin therapy, also known as combined hormone therapy, became the hormone treatment of choice for women who hadn't had hysterectomies, while estrogen alone was commonly used among women who'd had hysterectomies.

Meanwhile, it became clear that long-term hormone use had another effect besides curbing menopausal symptoms: It seemed to reduce hip fractures. Evidence mounted, and in 1991 the first International Consensus Development Conference on Osteoporosis concluded that hormone therapy was the only well-established measure that could significantly reduce the risk for fractures.

Many studies have demonstrated that hormone therapy can hamper bone loss and boost bone density. The Postmenopausal Estrogen/Progestin Interventions (PEPI) trial found that women on hormone therapies — estrogen alone or an estrogen-progestin combination — gained bone density. Over a three-year period, the bone density of the women taking hormones rose, on average, 4% at the spine and 2% at the hip. But women who weren't taking hormones lost bone, to the tune of 1.8% at the spine and 1.7% at the hip.

But a number of questions remained. Could hormone therapy prevent hip fractures? How does long-term hormone use affect heart disease? Could it increase the risk for breast cancer? A variety of studies looked at the long-term effects of hormone use.

It appeared that hormone therapy reduced the risk for colon cancer, but increased the risk for breast cancer and blood clots. A number of studies further explored the relationship between breast cancer and hormone therapy. Many found that hormone therapy slightly increased the likelihood of developing breast cancer, and that the risk compounded over time. For example, a January 2000 study revealed that a woman's increased risk for breast cancer climbed by 8% a year for each year of estrogen-progestin use. For women using only estrogen, risk increased by 1% per year. A month later, a study published in the Journal of the National Cancer Institute found that breast cancer risk rose 24% for every five years of combined hormone therapy use, compared with a 6% jump for women on estrogen alone.

Researchers also looked closely at the effects of hormone therapy on heart disease. At first, the news on heart disease was encouraging. The Nurses' Health Study found that women taking hormone therapy were at lower risk for cardiovascular disease, although there was some speculation that this was because, compared with women in general, the participants in this study led healthier lifestyles and were more apt to seek medical care. And a 1995 report from the PEPI trial found that hormone therapy improved HDL (good) cholesterol and lowered LDL (bad) cholesterol and clotting factors that contribute to heart disease and strokes. But the study didn't last long enough to determine whether these improvements paid off in fewer actual heart attacks, strokes, or blood clots. The picture began to darken in 1998, when the Heart and Estrogen/Progestin Replacement Study found that hormone therapy did not prevent heart attacks in women who already had heart disease. Moreover, women taking hormones had 50% more heart attacks during the study's first year. The women on hormones were also more likely to develop blood clots. The results shocked estrogen enthusiasts.

Hormone therapy takes another blow

But the debate was far from over. The links between hormone use and breast cancer and heart disease remained controversial. Enter the Women's Health Initiative. This landmark study was designed to help answer lingering questions about the long-term effects of hormone therapy. The two arms of the study examined the effects of estrogen-only and combined hormone therapy. Both trials came to abrupt ends when the health risks of taking the hormone therapies emerged.

In July 2002, the trial of Prempro, an estrogen and progestin formula, was closed after researchers found significant increases in breast cancer (29%), heart disease (24%), stroke (31%), and blood clots in the veins (107%) and lungs (113%). The trial did establish, however, that the combined hormone therapy reduces the risk for hip fractures (34%), spinal fractures (34%), and colorectal cancer (37%). The 16,000 women in the study were told to stop taking the medication. Similarly, women in the estrogen-only portion of the study were told to stop taking their pills in 2004 because of a nearly 40% increase in stroke risk. Like the estrogen-progestin combination, the estrogen-only formulation (Premarin) was found to raise the risk for stroke and decrease the risk for hip fracture. On the other hand, it didn't appear to affect heart disease risk in any way. At the time the study was halted, there wasn't an increase in breast cancer risk either.

While both of these studies established that hormone therapy could indeed reduce hip fractures, they led many women to abandon using this treatment for osteoporosis. For these women, the increased risk for breast cancer and heart disease wasn't an acceptable tradeoff for the reduced fracture risk, especially since other drugs can effectively prevent and treat osteoporosis.

Hormone therapy is certainly down, but it may not be out. Critics of these studies point out that only one hormone preparation was used in each arm of the Women's Health Initiative and that other formulas may not carry the same risks and benefits. Others note that the women in the study began taking the hormones long after the start of menopause and question whether the results may be different for women who take hormones earlier.

It's likely that hormone therapy will continue to make headlines in years to come. In the meantime, if you are considering hormone therapy, it's wise to weigh the potential risks carefully, identify your own health risks and concerns, and discuss the issue with your doctor.

Calcitonin

Calcitonin is approved only for the treatment, not the prevention, of osteoporosis. Generally, calcitonin is regarded as a less effective treatment because it doesn't build bone as robustly as other medications and it is unclear whether it helps prevent hip or wrist fractures.

Calcitonin, a hormone produced by the thyroid gland, helps regulate calcium by inhibiting osteoclasts. Calcitonin is also found in fish and birds, and salmon is the most common source of calcitonin used in medications. For the treatment of osteoporosis, it has been available in an injectable form since 1984 and as a nasal spray since 1995.

Although calcitonin has been tested in a large number of clinical trials and has been used to treat women with bone loss for many years, its effects are still somewhat uncertain. Women who take it usually have a slowing of bone loss or a slight increase in bone mass. It reduces the risk for spinal fractures, but hasn't been shown to lessen the risk for other kinds of fractures.

Experts have found that calcitonin is not as effective as other osteoporosis medications in building bone, and some studies indicate that the increase in bone density caused by calcitonin is temporary. This observation has led to speculation that the body may develop resistance to the hormone over time. One theory is that the body's immune system recognizes biochemical markers that identify calcitonin as having come from another species and eliminates it as a foreign substance.

Calcitonin's effect is limited to bones, so it is not linked to any other health benefits or risks. People who take calcitonin by injection generally experience more side effects than do those who use the spray. Side effects include flushing in the face and hands, dizziness, nausea, rash, and increased urination. The spray can cause a runny nose.

Parathyroid hormone

A synthetic hormone is another treatment available for osteoporosis. In November 2002, the FDA approved teriparatide (Forteo), a synthetic version of parathyroid hormone (PTH), for the treatment — not prevention — of osteoporosis in both men and postmenopausal women.

PTH is produced naturally in the body. It works in several ways to increase the amount of calcium in circulation. It promotes calcium absorption in the intestines and slows its excretion by the kidneys. It can also stimulate both bone formation and bone loss. While too much PTH accelerates bone loss, low doses of PTH given intermittently can increase bone mass and strengthen bone.

Unlike other osteoporosis medications that slow the rate of bone loss, PTH actually helps build new bone. It does this by increasing the activity and number of bone-building osteoblasts. As a result, it can increase bone mass dramatically; it's the only treatment that can potentially reverse bone loss. Studies have found that 21 months of treatment with teriparatide increased bone mineral density at the spine by 9.7% and at the hip by 2.6%.

Effects of parathyroid hormone (PTH) on bone These scanning electron microscopy pictures show bone biopsies taken from a 64-year-old woman, before (A) and after (B) PTH treatment. Improvements can be seen in interior structure (microarchitecture) and outer (cortical) thickness. Effects of parathyroid hormone (PTH) on bone Reproduced from J Bone Miner Res 2001; 16: 1846–1853 with permission of the American Society for Bone and Mineral Research

One study found that teriparatide was more effective than alendronate in increasing bone mineral density and decreasing fractures in postmenopausal women with osteoporosis. Teriparatide appears to reduce vertebral fractures by 65%–70% and to reduce nonvertebral fractures by about 50%.

While there was speculation that combining teriparatide with a bisphosphonate may improve the effects of the drugs, a study published in 2003 in the New England Journal of Medicine found that this was not the case. In the study, 83 men were assigned to one of three groups: one that took teriparatide, one that took alendronate, and one that took both. The researchers found that the men who took only teriparatide had the greatest gains in bone mineral density at the spine and hip, compared with the men in the other two groups. Thus alendronate appears to dampen the benefits of PTH. But the researchers also found that the men on combination therapy had greater gains in spinal bone mineral density than those taking only alendronate. So this study found that PTH therapy alone seems to be most effective at increasing bone density, while combination therapy works better than alendronate alone.

Teriparatide is currently recommended for people who have osteoporosis and are at high risk for a fracture. This includes people who have already suffered a nontraumatic fracture of the spine, hip, or another major bone, as well as people with multiple risk factors for fractures (such as a family history of osteoporosis, poor calcium intake, and a T-score of less than -2.5 on a bone mineral density).

Teriparatide is only available as a once-a-day injection. Because this is a new therapy and no long-term studies are available, most experts recommend that treatment be limited to no more than two years. Some experts recommend using PTH alone for two years and then using a bisphosphonate to protect or augment any gains in bone mineral density.

Side effects can include nausea, dizziness, and leg cramps. In animal studies, some rats that were given PTH developed a form of bone cancer, but in human studies, no cases have appeared.

Source: from Harvard Health Publications, Copyright © 2008 Harvard University. All rights reserved. Harvard Medical School does not endorse products.
Used with permission of StayWell.
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