Learning Objectives     1. Discuss how osteoporosis can strike even women in premenopausal age.     2. Define amenorrhea and its effect on osteoporosis.     3. Describe how estrogen helps a woman attain peak bone mass.     4. Describe the effect of drugs, calcium intake, smoking and physical exercise on bone mass.     5. List 6 osteoporosis prevention and treatment strategies for menopausal women.

Everyday, the National Osteoporosis Foundation hears from another young woman who has been diagnosed with osteoporosis. These women are between the ages of 25 and 50 and are premenopausal. How, they ask, can they possibly have osteoporosis?

Even though osteoporosis is a disease that is usually diagnosed in postmenopausal women, it knows no age boundaries. In fact, young women do develop osteoporosis. While genetics and heredity play a major role in a person's ability to attain peak bone mass, there are several medical conditions that develop in childhood, adolescence, and young adulthood that can also interfere with a woman's ability to achieve her optimal bone mass and put her at risk for premenopausal osteoporosis. Osteoporosis is characterized by low bone density and deterioration in the microarchitecture of the bone which makes the skeleton weak.

Attaining Peak Bone Mass

Estrogen

It is well known that estrogen protects against bone loss. Conversely, estrogen deficiency, especially in young women, plays a role in the attainment of peak bone mass. Amenorrhea, the absence of menstrual cycles, is the most common cause of estrogen deficiency in premenopausal women. Amenorrhea occurring for as short a time as six months may result in significant loss of bone mass.

In women, the ovaries mature at puberty and produce estrogens and other hormones. Estrogen plays an important role in normal bone growth and the attainment of peak bone mass. The majority of bone mineralization occurs during a woman's second decade of life which coincides with the onset of puberty and regular menstrual cycles. Some studies have shown that there is a relationship between a woman's attainment of peak bone mass and the number of menstrual cycles she experiences during her reproductive years. As a result, women with amenorrhea, regardless of the cause, may never achieve their optimal bone mass.

There are two types of amenorrhea: primary and secondary. Primary amenorrhea occurs when menstrual periods fail to appear by age 16. Secondary amenorrhea, which is the most common form of this disorder, is diagnosed when menstrual periods, previously established in puberty, stop for a time period of three or more months. While primary amenorrhea may be caused by a congenital defect such as Turner's Syndrome, a condition in which a woman is born with one X chromosome instead of two and does not have ovaries, most cases of amenorrhea are caused by conditions that alter the woman's normal reproductive cycles.

Each year, more than 250,000 women between the ages of 15 and 50 have their ovaries removed, causing them to become estrogen deficient. Amenorrhea may also result from a hormone imbalance caused by a disorder of the hypothalamus (a part of the brain) or pituitary gland, or it may result from physical or psychological stress. Physical or psychological stress may result in an eating disorder such as anorexia nervosa that leads to abnormally low body weight, or as exercise-associated amenorrhea resulting from a combination of over-exercise, low body fat, and dieting.

Eating disorders cause malnutrition and affect almost every system in the body. In addition to causing amenorrhea, they also interfere with the body's production of other hormones that play a role in bone health. Estrogen deficiency has the most damaging effect on bone, but anorexia also interferes with the body's production of growth hormone and other growth factors such as IGF-I which stimulate bone formation. At the same time, the adrenal glands produce excess amounts of the glucocorticoid cortisol which is known to cause bone loss. Finally, the malnutrition associated with anorexia deprives the body of essential nutrients, including calcium. Calcium is essential for bone growth and development. It is also necessary for several life-sustaining functions such as normal heart activity, blood clotting, muscle contractions, and more. When the body does not get enough calcium from food sources, it removes the calcium it needs from the bones.

Those women who recover from an eating disorder at a young age (younger than 15) may have normal total body bone mineral density (BMD), but the BMD in the spine and hip may remain low. However, the longer anorexia persists, the more likely it is that BMD will not return to normal.

Exercise-associated amenorrhea is common, especially in marathon runners, gymnasts, and ballet dancers. The exact relationship between exercise and the cessation of menstrual cycles is unknown. However, it is likely that over time, an inadequate caloric intake for the amount of energy expended in physical exercise interferes with hormonal activity that is responsible for the normal secretion of estrogen. As the estrogen level declines, so does BMD which increases the woman's risk for developing osteoporosis and fracturing bones. However, with normal estrogen levels, a reasonable program of regular exercise and a well-balanced diet are clearly beneficial for maintaining bone mass.

Medication-Induced Bone Loss

Many chronic illnesses require long-term use of medications that are known to cause bone loss. One class of drugs that causes bone loss is glucocorticoids such as prednisone or cortisone. These medications are often beneficial in the treatment of arthritis, asthma, colitis, lupus, and many other diseases. However, glucocorticoids are known to accelerate bone loss, decrease the amount of calcium absorbed from food, and increase the loss of calcium in the urine. Also, several anti-convulsant medications affect bone health. These drugs are often prescribed for epilepsy or other seizure disorders. Many of these diseases begin during childhood, adolescence, or early adulthood, the most critical periods for bone growth. Women who must use these medications should have their bone health monitored carefully.

Excessive thyroid hormone has also been shown to cause bone loss. Thyroid hormone is used to treat an underactive thyroid gland as well as other thyroid disorders. However, bone loss in response to excess thyroid medication can be prevented by monitoring a person's thyroid hormone levels through a Thyroid Stimulating Hormone (TSH) blood test. This test can help ensure that hormone levels stay within the normal range and bone loss does not occur.

Do not discontinue or change the dose of any medications without first discussing your concerns with your doctor. Lifestyle Behaviors

Calcium Intake

Inadequate calcium intake plays a role in achieving and maintaining optimal BMD throughout life. The average American woman consumes less that 50% (500 mg.) of the recommended daily allowance (RDA) for calcium. Girls age 12-19 get less than 70% of the RDA, which is 1,200-1,500 mg. for this age group. When calcium intake falls below that needed by the body, calcium is taken from the bones.

Smoking

A recent study of female twins suggested that a woman who smokes one pack of cigarettes daily may experience a 5%-10% reduction in BMD by the time of menopause. Tobacco smoking has also been shown to interfere with ovarian function and may lead to an early menopause (up to two years earlier) and more rapid bone loss in the early postmenopausal years. Studies have also suggested that estrogen replacement therapy (ERT) may be less effective in women who smoke.

Physical Exercise

Exercise is an important part of an osteoporosis prevention and treatment program. Regular weight-bearing exercise and resistance or weight-training are key factors in the achievement and maintenance of peak BMD.

Prevention and Treatment Strategies

PConsume an optimal calcium intake as determined by the National Institutes of Health Consensus Development Panel on Optimal Calcium Intake, 1994 of 1200-1500 mg/day between ages 11 and 24, and 1,000 mg/day between ages 25 and 65 if taking estrogen and 1500 mg/day if not taking estrogen.

PEnsure a daily intake of at least 400 but not more than 800 IU of vitamin D.

PParticipate in regular weight-bearing exercise and weight-training.

PDo not smoke.

PKeep a diary of menstrual history. Report irregularities or missed cycles to your physician so that appropriate hormone tests can be done to determine the cause of menstrual irregularities.

PSome physicians may treat amenorrhea with oral contraceptives, especially if amenorrhea is persistent. Oral contraceptives may have a beneficial effect on the BMD in young women, although studies on the effectiveness of this as a treatment are contradictory. In some women, estrogen intervention will result in a slight reversal of bone loss. For this reason, it is important for the doctor to focus on successfully treating the underlying condition. Women who have persistent menstrual irregularities may wish to have a bone density test to determine their bone health.

For amenorrheic athletes who have experienced bone loss, a decrease in the amount and the intensity of training, an increase in total calories and calcium consumed, and the resumption of normal menstrual periods are goals of treatment. A program of resistance training designed to increase both muscle strength and mass may also improve bone health in these athletes. Finally, ERT may be indicated for those women who are not willing to make changes in their exercise or dietary patterns. While there are no clinical trials studying the most effective bone-preserving dose of ERT for premenopausal women, it is generally accepted that the doses prescribed for postmenopausal women should be adequate for reducing bone loss in amenorrheic athletes.

Education

Every person should be aware of, and practice, the behaviors that impact skeletal growth in the first 20 years of life when peak bone mass is achieved. Since a regular menstrual cycle and proper nutrition are major factors in the development, attainment, and maintenance of peak bone mass during adolescence and young adulthood, it is important to share this information and these prevention strategies with daughters, nieces, and other young women whenever possible.

Source: National Osteoporosis Foundation