Osteoporosis is a systemic skeletal disease characterized by microarchitectural deterioration of bone tissue with a resultant increase in fragility. This leads to an increased risk of fractures, which may occur even in the absence of significant trauma. Approximately 13-18% of U.S. women aged 50 years and older have osteoporosis while another 37-50% have low bone mass (osteopenia). Both osteopenia and osteoporosis increase the risk of fracture. Although hip fracture has been properly emphasized as a source of significant morbidity and mortality (15-20%), the more common thoracic spine fracture accounts for significant morbidity, including pain; deformity; loss of independence; and reduced cardiovascular, respiratory, and even digestive function. Osteoporosis is a largely preventable complication of menopause. Appropriate screening strategies and significant pharmacologic interventions are available to prevent and treat osteoporosis.

Bone mineral density testing is the preferred method to establish the diagnosis of osteoporosis. Bone mineral density is a strong predictor of fracture risk because bone mass accounts for 75-85% of the variation in bone strength.

Bone mass peaks at approximately age 30 years in both men and women. After reaching peak bone mass, approximately 0.4% of bone is lost per year in both sexes. In addition to this loss, women lose approximately 2% of cortical bone and 5% of trabecular bone per year for the first 5-8 years after menopause.

Factors Affecting Bone Mass

Bone mass is influenced by numerous factors . Some of these factors are modifiable (eg, cigarette smoking) while others are not (eg, family history of hip fracture). Other factors may affect the risk for fracture but not necessarily the predisposition to osteoporosis (eg, propensity to fall).

The single largest factor influencing a woman’s maximal or peak bone mass is genetics. First-degree relatives of women with osteoporosis have lower bone mass than those with no family history of osteoporosis.

Many studies have shown that the risk of osteoporosis is greater for Caucasian and Asian women than for African-American women. Mexican-American women have an intermediate risk of osteoporosis.

There is general agreement that weight-bearing exercise confers a positive effect on the skeleton, but during early menopause, weight-bearing exercise alone is insufficient to prevent bone loss. However, weight-bearing exercise will slow the rate of bone loss. Growing evidence suggests that impact-loading exercises (ie, weight-lifting in contrast to water aerobics) provide the greatest osteogenic stimulus. Lack of physical activity is associated with rapid and significant bone loss.

Certain diseases or medical conditions and certain drugs are known to be associated with bone loss.

Screening Methods

Dual-energy X-ray absorptiometry is the technical standard for measuring bone mineral density. Dual-energy X-ray absorptiometry is preferred because it measures bone mineral density at the important sites of osteoporotic fractures (especially the hip), is relatively inexpensive, has high precision and accuracy, and has modest radiation exposure.

When should screening for osteoporosis be initiated?

Although not all experts or organizations agree, the following guidelines can be recommended:

  • Bone mineral density testing should be recommended to all postmenopausal women aged 65 years or older.
  • Bone mineral density testing may be recommended to postmenopausal women younger than 65 years who have 1 or more risk factors for osteoporosis.
  • Bone mineral density testing should be performed on all postmenopausal women with fractures to confirm the diagnosis of osteoporosis and determine disease severity.

Bone mineral density testing may be useful for premenopausal and postmenopausal women with certain diseases or medical conditions and those who take certain drugs associated with an increased risk of osteoporosis. In the absence of new risk factors, subsequent screening should not be performed more frequently than every 2 years.

Can lifestyle changes prevent osteoporosis and osteoporosis-related fractures?

Sedentary lifestyle is associated with reduced bone mass. The benefits of physical exercise include maintenance of bone mass and an increase in muscle strength and coordination.

The risk of falling increases substantially with aging. Diseases and sensory impairments that can cause falling should be evaluated and treated (eg, a history of falls, fainting, or loss of consciousness; muscle weakness, dizziness, or balance problems; and impaired vision). Medications that reduce strength and balance (such as sedatives, narcotic analgesics, anticholinergics, and antihypertensives) should be avoided, if possible. The living environment should be monitored to reduce the risk of falling. Safety hazards in the home and at work, such as loose rugs and carpets; obstacles, especially to stairs; and poor lighting, should be assessed to reduce the risks of falls. Individuals at risk should consider installing handrails in and around the home.

Cessation of smoking and reducing alcohol intake may contribute to a decreased risk of developing a fracture. Heavy alcohol consumption (defined as 7 oz or more per week) has been shown to increase the risk for both falls and hip fracture. Excessive alcohol consumption also has detrimental effects on bone mineral density. However, moderate alcohol consumption in women aged 65 years and older is associated with increased bone mineral density and lower risk for hip fracture.

Is there a role for estrogen and progestin for the prevention or treatment of osteoporosis?

The Women’s Health Initiative initial study results demonstrated a statistically significant reduction in fractures, including hip fractures, in a large group of otherwise healthy women using hormone therapy. A detailed analysis of the data from this study has not been published to date, so it is not clear whether this was truly a prevention or a treatment population.

Although the risks of long-term use of estrogen or hormone therapy are small, many recommend such therapy be used for the shortest period at the lowest possible dose. The Women’s Health Initiative study indicated a significantly increased risk of cardiovascular events and breast cancer for women taking combined estrogen and progestin therapy. Thus, the use of hormone therapy for osteoporosis prevention or fracture reduction should be evaluated based on an individual woman’s history and risk factors, including the need for treatment of vasomotor symptoms.

When estrogen therapy is discontinued, how should a woman be monitored for osteoporosis risk?

When a woman discontinues estrogen therapy, risk assessment and screening should follow the same criteria as for a woman who is in the early stages of menopause. It also should take into account the need for bone mineral density measurements based on age and other risk factors for osteoporosis.

Is other pharmacotherapy beneficial for the prevention and treatment of osteoporosis?

In addition to estrogens, there are a number of agents available for the prevention of osteoporosis. These can be broadly grouped into 2 categories: 1) bisphosphonates (ie, alendronate, risedronate) and 2) selective estrogen receptor modulators (SERMs) (ie, raloxifene, tibolone, tamoxifen).

Combinations of Antiresorptive Therapies

In women, calcium and vitamin D consumption are frequently inadequate. Doses vary by source and chemical composition (eg, carbonate, citrate, gluconate), which may affect bioavailability. The recommendations for these supplements apply to elemental calcium. Care should be made to advise patients of the differences in elemental calcium content (usually on the product label) in an attempt to make sure they ultimately receive enough calcium.

Are complementary and alternative therapies beneficial for the prevention of osteoporosis?

Although some data suggest that isoflavones (a class of phytoestrogens found in rich supply in soy beans and soy products as well as in red clover) may favorably affect bone health, few randomized, controlled clinical studies with humans have been conducted, and those that have all involved small numbers of subjects in trials of short duration.

When should treatment for osteoporosis begin and how should patients be followed?

Lower bone mineral density T scores generally indicate more severe osteoporosis and higher risk of fracture. Although few would withhold treatment from a women with osteoporosis (T score less than -2.5), whether to treat a women with higher bone density scores has become subject for debate. The controversy focuses on the extremely low risk of fracture in young women with osteopenia and all women without additional risk factors. The high costs and potential side effects of long-term therapy until “old age,” when fracture risk increases, has led many to suggest withholding treatment until certain treatment thresholds have been reached.

Repeat DXA testing in untreated postmenopausal women typically is not useful until 3-5 years have passed because 5-year postmenopausal bone mineral density reductions average only approximately 0.5 standard deviations from the mean (both T scores and Z scores) in that time frame. For women receiving osteoporosis therapy, bone mineral density monitoring before 2 years of therapy are completed does not provide clinically useful information and may lead to erroneous assumptions about the effect of therapy.

References available upon request.

This excerpt from ACOG’s Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists Number 50, is provided for your information. It is not medical advice and should not be relied upon as a substitute for visiting your doctor.

ACOG materials are reviewed approximately every 18-24 months.

Copyright © January 2004 The American College of Obstetricians and Gynecologists. All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher.