The Basics of Osteoporosis

Osteoporosis is a preventable and treatable disease that thins and weakens your bones, making them fragile and more likely to break. It is sometimes called a "silent disease" because it can occur gradually over many years without your knowledge. Often the very first symptom of osteoporosis is a broken bone, also called a fracture, which usually happens at the hip, spine or wrist. But the good news is that osteoporosis can be prevented and treated.

The vast majority of individuals affected by osteoporosis are women. As many as eight million American women have osteoporosis, and almost 22 million have low bone density or low bone mass, putting them at risk for developing the disease, estimates the National Osteoporosis Foundation. Healthy bone, which stores 99 percent of the calcium in the body, is strong with many interconnecting pieces. In contrast, when a woman loses bone density or bone mass, some bone is dissolved, leaving bone structure porous — almost like a honeycomb of large empty spaces within the bone.


Although the disease can strike at any age, you're at greatest risk for fractures from osteoporosis after menopause. Half of all Caucasian women will have an osteoporotic fracture, according to the National Osteoporosis Foundation. That's because women's bodies produce less estrogen after menopause, and estrogen plays an important role in helping to prevent bone loss.

Although the average age for menopause in the U.S. is 51, some women experience menopause earlier due to natural causes or following surgery, illness or treatments that destroy the ovaries. For example, a total hysterectomy in which the ovaries and uterus are removed will immediately trigger menopause. When you have not had a menstrual period for more than 12 consecutive months, you are postmenopausal.

Understanding osteoporosis

To understand osteoporosis, you must understand how your bones develop and change throughout your lifetime. Bone is complex, living tissue containing three different types of cells, proteins and minerals. It is made mostly of collagen, a protein that provides a soft framework, and hydroxyapatite, a complex of calcium and phosphate, minerals that add strength and harden the framework. This combination of collagen and calcium makes bone strong yet flexible to withstand stress.

Your bone provides structural support for muscles, protects vital organs and stores the calcium essential for bone density and strength. It changes regularly, through a process called remodeling, in which the body breaks down old bone and replaces it with new, strong bone. This process continues throughout life, but varies significantly as you age.

From birth to age 25 or 30, the body builds more new bone than it breaks down. By age 30, your bones become the strongest they will ever be. This phase of bone health is called peak bone mass. The level of bone mass achieved at the peak is determined largely by genetics, but also by nutrition, exercise and menstrual function. After this age, your bones begin to lose more calcium than they retain, making them more porous and fragile. This process speeds up dramatically as menopause approaches and for several years after.

Following menopause, you can lose up to 30 percent of bone mass. Bone loss continues at a slower pace throughout the remainder of your life perhaps accelerating again in the elder years. Rates of bone loss vary among individuals but even slow rates may be dangerous, especially in women who start with low bone mass prior to menopause.

Copyright 2003 National Women's Health Resource Center Inc. (NWHRC).