The word “osteoporosis” literally means “porous bones.” With osteoporosis, bones become weak and brittle—so brittle that even mild stresses, such as bending over to pick up a book, pushing a vacuum, or coughing, can cause a fracture.

The strength of your bones relates to their mass or density and is in part due to the calcium, phosphorus, and other mineral levels. In osteoporosis, the strength is decreased as calcium and other minerals are slowly depleted and bone density is undermined.

Bone is living tissue that is continually changing—new bone is made and old bone is broken down, a process called “remodeling” or “bone turnover.” The cells called osteoclasts dissolve or “resorb” old bone cells, leaving tiny cavities.

Another type of bone cells, called osteoblasts, line or fill these cavities with a soft honeycomb of protein fibers that become hardened by mineral deposits. A full cycle of bone remodeling takes 2 to 3 months. When you are young, your body makes new bone faster than it breaks down old bone, and bone mass increases.

Peak bone mass is reached in your mid-30s. The mineral-hardened honeycomb, which accounts for bone strength, depends on an adequate supply of calcium. Estrogen also plays a key role in bone health by slowing the resorption of old bone and promoting new growth.

With aging, bone remodeling continues, but people lose slightly more than they gain. At menopause, when estrogen levels decrease, bone loss accelerates to 1 to 3 percent per year.

Around age 60, bone loss slows again but it does not stop. Men can also have osteoporosis. By an advanced age, women have lost between 35 and 50 percent of their bone mass, and men have lost 20 to 35 percent.

Despite the gloomy statistics, osteoporosis is not an inevitable part of aging. With identification of the major causes of the disease and their risk factors, osteoporosis can be detected early and treated.

Moreover, a greater understanding of the role of nutrients and hormones and new and continually emerging medications are raising hopes for prevention of the disease. How do you assess your personal chances for getting osteoporosis? Listed below are several risk factors that should be considered and evaluated:

• Sex—One’s sex is the most significant indicator of risk. Fractures from osteoporosis are about twice as common in women as in men. Women build less bone than men by early adulthood. Women also generally consume less calcium than men. Prolonged calcium deficiency is a risk. Moreover, studies have documented a tendency for low calcium intake among adolescent girls—a time at which calcium is especially needed for bone development.

• Family history—Having a mother or sister with the disease may increase your risk.

• Race—Whites are at greatest risk, followed by Hispanics and Asians. African-Americans have the lowest risk. Whites have a higher risk because they generally attain a lower peak bone mass than the others.

• Age—The older an individual, the higher the risk for osteoporosis.

• Small body frame—In general, the smaller the body frame, the thinner the bone.

• Lifestyle choices—Smoking increases bone loss, perhaps by decreasing the amount of estrogen the body makes and reducing the absorption of calcium in the intestine. In addition, women smokers tend to enter menopause earlier than nonsmokers—a significant risk factor in itself.

Consumption of too much caffeine or alcohol can lead to bone loss. A sedentary lifestyle is a risk factor. Weightbearing physical activity strengthens bones. Prolonged calcium deficiency does not merely mean that newly consumed calcium is not going into the bones.

Because the body also needs calcium circulating in the blood, it will “rob” calcium from the bones to provide adequate calcium in the blood.

• Estrogen deficiency—The less a woman’s lifetime exposure to estrogen, the higher her risk for osteoporosis. For example, a woman will have a higher risk if she has an early menopause or began menstruating at a later age. Early menopause due to surgical removal of the ovaries also increases the risk for osteoporosis.

Women generally experience a sudden drop in estrogen at menopause, which accelerates bone loss. Men experience a much more gradual decline in the production of testosterone, and therefore they do not experience as rapid a loss of bone mass.

Recent evidence suggests that estrogen also may play an important role in bone metabolism in men. There also can be a deficiency of estrogen as a result of very low weight caused by eating disorders such as anorexia nervosa or excessive physical activity.

• Immobilization—This robs bones of the weight-bearing exercise that can help to build bone mass. Someone who is bedridden or otherwise off their feet for any extended period could have such a problem.

• Medications—Some medications can contribute to osteoporosis. Long-term use of corticosteroids, such as prednisone, cortisone, prednisolone, and dexamethasone, is very damaging to bone.

People who need to take such medications for other conditions (for example, asthma, rheumatoid arthritis, or psoriasis) should have their bone density monitored because they may require treatment to slow the rate of bone loss.

Too much thyroid hormone caused by an overactive thyroid gland or excess thyroid replacement also can cause bone loss. In addition, other medications also can adversely affect bone health. If you are at risk for osteoporosis, your physician will take this into account when prescribing medications.