A Few Thoughts about Bone Density

Young men may feel invulnerable, but as men get older, they grow wise to the ways of the body. As the years pile on, men begin to worry about heart disease, high blood pressure, diabetes, stroke, cognitive decline, and prostate disease - all with good reason. Faced with so many concerns, most gents are only too happy to cross "women's diseases" off their worry lists. It's understandable, but in the case of osteoporosis, it's a big mistake.

Hard facts

Although osteoporosis is more common in females than males, it's not a woman's disease. In fact, about two million American men have osteoporosis and another 12 million are at risk. Because osteoporosis starts later in men than women, most men with "thin bones" are over age 65. All in all, about one in every five 50-year-old men will suffer an osteoporotic facture during his remaining years. Hip fractures are particularly common and are more serious for men than women, with a one-year mortality rate of up to 37.5%.

So, if you think osteoporosis is a woman's disease, think again. Then think about ways to prevent, recognize, and treat this important disease of men and women.

Healthy bones

Healthy bones are amazingly strong; ounce for ounce, they can support as much weight as reinforced concrete. But your bones have to be smart as well as strong. Unlike concrete, they have to grow and repair themselves after injuries. They do this by constantly remodeling.

Your body's bones are metabolically active living tissues. Cells called osteoblasts are constantly at work forming new tissue and depositing calcium to keep bones strong. At the same time, osteoclasts are resorbing old bone and removing calcium. At any one time, about 7% of your body's bone calcium is on the move.

In youth, bone formation outpaces resorption - that's how we grow. In males, bone calcium density increases rapidly when testosterone levels surge at puberty. Bone strength peaks at about age 20 and remains stable for the next 10 to 15 years as bone formation and resorption continue at a balanced rate. The average young adult has about two to four pounds of calcium in his 206 bones. Young men with strong bones have a reduced risk of developing osteoporosis later in life; boys with delayed puberty, dietary deficiencies of calcium or vitamin D, or insufficient exercise levels have lower peak bone densities and are at increased risk for osteoporosis when they get older.

Youth never lasts, and neither do peak bone densities. In both men and women, bone resorption begins to outpace bone formation at about age 35. At first, bone density declines slowly. But when women reach menopause, their estrogen levels plummet; because sex hormones help put calcium in bone, bone density decreases sharply. In men, though, testosterone levels decline more gradually, dropping just 1% a year beyond age 40. As a result, bone loss remains relatively slow - but it is steady. Beyond age 65 or so, men and women lose bone at about the same rate. Over time, the average man will lose about 20% of his cortical bone and 30% of his trabecular bone. And in some men, bone loss is even more substantial, crossing the line that separates men with healthy bones from those with osteoporosis.

Brittle bones

Osteoporosis is well named: in this disease, bones become porous because they lack enough calcium to maintain their structural integrity. In addition to having a low calcium density, osteoporotic bones develop architectural abnormalities. In healthy bones, normal bone mineral density accounts for about 70% of bone strength, and normal architecture contributes about 30%. The combination of low calcium and poor bone quality produces weak bones that are easily fractured, with or even without trauma.

Osteoporosis

Osteoporotic bones are weak and susceptible to fractures because they lack the calcium and scaffolding that make healthy bones strong.

Risk factors

Two of the most important determinants of a man's bone density are beyond his control. Genetic factors explain up to 80% of the variance in peak bone density in young men; the gene that regulates vitamin D's activity appears to be the most important, which makes sense since vitamin D helps the intestines absorb calcium from the bloodstream. Genetic factors explain why osteoporosis tends to run in families and why the disease is more common in Caucasians and Asians than in African Americans.

The second major determinant of bone density in men is age; beyond the fourth decade of life, bone density declines progressively in every man. But if men can't control their heredity or slow the tick of the clock, they can modify many of the other osteoporosis risk factors listed in the table below.

Medical factors account for the most severe cases of osteoporosis in men. Low testosterone heads the list, explaining about 15% of cases severe enough to cause fractures. Therapy with prednisone and related drugs is a close second at 13%. Alcohol abuse is the most common lifestyle contributor, explaining 6% of cases. But in about half the men with osteoporosis, no specific causal abnormality can be identified. Diet and exercise are of major importance for these men diagnosed with primary osteoporosis - just as they are for all men.

Factors that increase the risk of osteoporosis in men:

Genetic factors

*Family history of osteoporosis

*Caucasian or Asian heritage

Lifestyle factors

*Smoking

*Excessive alcohol consumption (over two drinks a day)

*Lack of exercise

Dietary factors

*Insufficient calcium

*Insufficient vitamin D

*Excessive vitamin A (over 3,000 IU or 900 mcg a day)

*Excessive caffeine (can be offset by sufficient dietary calcium)

*Excessive protein consumption, especially animal products

Hormonal factors

*Hypogonadism (low testosterone level)

*Overactive thyroid, parathyroid, or adrenal gland

*Growth hormone deficiency

*Advancing age

*Thin body build and weight loss

Medical conditions

*Elevated levels of homocysteine (an amino acid in the blood)

*Chronic kidney, liver, or lung disease

*Chronic intestinal disorders

*Certain malignancies (myeloma, lymphoma)

Medications

Androgen-deprivation therapy for prostate cancer

*Prednisone

*Certain antiseizure medications

*Certain chemotherapy drugs

*Proton pump inhibitors (used to block gastric acid production)

*Selective serotonin reuptake inhibitors (used to treat depression)

*Thiazolidinediones (used to treat diabetes)

*Warfarin (an anticoagulant)

Symptoms

Until it's quite advanced, osteoporosis is a truly silent disease. A decreasing bone density does not produce any symptoms until it declines below the fracture threshold. Even then, osteoporosis is often painless until soft bones meet up with hard objects; legs strong enough to slide into second base at age 17 may snap from a simple stumble at 70.

In men, as in women, spine fractures are the most common consequence of osteoporosis. A gradual loss of height may be the only evidence of compressed vertebral bones, but back pain is also common and can be very severe. In advanced cases, a characteristic stooped posture and protuberant waist testify to osteoporotic spinal fractures. In women, the deformity is called a dowager's hump; although it's also a problem for men, it doesn't have a common name that's appropriate for males.

In both men and women with osteoporosis, the hip and the wrist follow close behind the spine on the fracture list. Rib fractures appear to be a bit more likely in men, but osteoporosis victims of either gender can fracture any of their bones.

Height loss and the heart

Most men lose height as they age. The spinal column is composed of a set of 24 bones, the vertebral bodies, and the disks that lie between them. Height loss is usually caused by a combination of compressed vertebral bodies due to loss of bone calcium plus compression of the discs due to aging elastic tissue. But men who lose two inches or more should get a DXA scan for osteoporosis. And a British study found that height loss is linked to an increased risk of coronary artery disease and an elevated death rate.

Diagnosing osteoporosis

Surprisingly, perhaps, ordinary x-rays are not reliable for detecting osteoporosis. But other methods are quite accurate and are now widely available. Dual energy x-ray absorptiometry (DXA) is the standard test. It's quick, safe, and painless, taking only 10 minutes. While you lie on a table, a machine beams photons through your bones, usually at the spine, hip, or wrist. DXA can compute the bone density in any region of your body, and it exposes you to only one-tenth as much radiation as a chest x-ray. Ultrasound, which uses sound waves to measure bone mineral density at the hip, shin, heel, or finger, is another test. It is not as accurate as DXA, but it can give a rough estimate of bone density painlessly in less than a minute.

For years, the National Osteoporosis Foundation has recommended DXA testing for all women age 65 and older and for all postmenopausal women under age 65 who have one or more risk factors. In 2008, the foundation added similar guidelines for men, setting the age for routine testing at 70. Younger men who have risk factors should also be tested.

Testing is particularly important for men undergoing androgen-deprivation therapy for prostate cancer and for men who have suffered fractures, particularly if only minor trauma was involved. Men who have lost more than two inches of height, who have fewer than 20 teeth, and who are extremely thin (body mass index of 19 or lower) should also be tested. If you have a spinal curvature that prevents you from touching the back of your head to a wall while you stand with your heels and back against the wall, you should have a DXA test.

Getting a DXA is one thing, interpreting your results, another. Although the standards have been developed chiefly from studies of women, they can be applied to men as well.

Men at risk for osteoporosis may benefit from additional testing to hunt for underlying abnormalities. Useful studies can include blood or urine tests for anemia and abnormal proteins, liver and kidney disease, calcium, vitamin D, and hormones such as testosterone, thyroid and parathyroid hormones, and cortisol. Many specialized tests are also available - but in most men, testing is less important than treatment.