What does menopause have to do with osteoporosis? Are there different kinds of osteoporosis?
There are actually two types of osteoporosis: primary osteoporosis and secondary osteoporosis. Either type can affect men, women, and children. Primary osteoporosis is age-related and affects women more severely and earlier in life than men. Secondary osteoporosis is caused by other disease processes or medications used to treat various diseases or problems. Secondary osteoporosis is also more common in women because the illnesses that cause bone loss or the problems that require medications that affect bone remodeling more often affect women.
Primary osteoporosis, although occurring in both men and women, is age-related and tends to occur mostly in women and about 10 years earlier than in men. This is because the rate of bone loss is different in women than in men. Women rapidly lose bone in the 4 to 8 years after menopause, and then continue with a slower rate of bone loss like men, who also experience bone loss over many years. Bone loss from primary osteoporosis is most common in the hip, but can affect all bones in the body.
Hormones such as estrogen and testosterone that are important for bone growth and for maintaining bone mass.
Primary osteoporosis affects the entire skeleton, particularly in women following menopause. Natural menopause is medically defined as the specific point in time occurring after 12 consecutive months without a menstrual period that does not have another identifiable cause, such as illness or medication. Postmenopause, the time following menopause, is when many women develop osteoporosis. The decrease in bone mass in postmenopausal women is a direct result of the loss of estrogen. Menopause for any reason (e.g., surgery, chemotherapy) can cause bone loss.
Postmenopausal women lose about 2% and sometimes even up to 5% of their bone mass per year for the first 4 to 8 years following menopause. Twenty percent of their total bone loss takes place in those first 4 to 8 years after menopause. The majority of White women can expect to have osteopenia or osteoporosis once they have been in postmenopause for 10 years.
Because primary osteoporosis is caused mostly by estrogen loss in women, one of the preventive treatments for primary osteoporosis in women is estrogen therapy (ET). Estrogen (with or without progesterone) is usually prescribed to prevent osteoporosis only if the woman also has significant other symptoms of menopause such as hot flashes and night sweats. When estrogen therapy is used for the relief of menopause symptoms, it is called menopause hormone therapy (MHT). If you have a uterus, progesterone must be added to the estrogen therapies (see Question 64). An estrogen patch is also available to prevent the bone loss associated with postmenopause. Recent studies indicate that this patch effectively reduces hot flashes as well (see Question 65).
Which bones are affected by osteoporosis?
Although the hipbones and the vertebrae (bones of the spine) provide the best measurements of bone loss, osteoporosis occurs in all bones. The osteoblasts and osteoclasts are most active in the bones of the body's central region—that is, bones of the hip and vertebrae— and the long bones of the arms and legs. The skull bone is very rarely affected by osteoporosis.
Fractures of the hip and vertebrae are also the most common fractures. Because all bones can be affected by osteoporosis, clinicians usually recommend that individuals with weakened bones, like those caused by osteoporosis and osteopenia, avoid playing certain sports or engaging in certain activities that will increase the likelihood of falls which, of course, increase the risk of fractures of any bones, but particularly the hip (see Question 44).
Every bone has a soft inner portion known as the bone marrow as well as an outer portion made up of trabecular bone (connective spongy bone tissue) and cortical bone (the hard outer shell). Trabecular bone makes up the softer inner shell of all bones and is present in higher amounts in the hip, vertebrae, wrists, and ends of the long bones. The central and long bones have more trabecular bone than the other smaller bones in the body. Trabecular bone, which comprises about 20% of the body's bone, provides strength and integrity, produces blood products, and provides the surface used for mineral exchange, such as phosphorus and calcium. Bone marrow is found in the spaces between trabecular bone. Cortical bone makes up the hard outer shell of bone and is critical for bone strength. Figure 5 shows trabecular and cortical bone.
Sweating that occurs at night resulting from hot flashes during perimenopause and postmenopause.
Figure 5 Cortical and trabecular bone. Courtesy of Eli Lilly and Company, Einhorn TA, The Bone Organ System in: Osteoporosis. Eds. Marcus et al. Academic Press 1996.
In primary osteoporosis, women lose 5% to 10% of cortical bone and 20% to 30% of trabecular bone during the rapid bone loss occurring in the 4 to 8 years following menopause. In contrast, men and women (after the faster postmenopausal bone loss) experience a slower rate of bone loss as a result of aging. Occurring slowly over many years, this type of bone loss accounts for about a 20% to 25% loss of both cortical and trabecular bone. Thus, women are at risk for much greater bone loss than men.