Osteoporosis, a condition marked by reduced bone density and heightened fracture susceptibility, disproportionately affects postmenopausal women. Central to this ailment is estrogen's pivotal role in bone homeostasis.
This article explores the nuanced interplay between estrogen and bone health, shedding light on preventive measures and treatment avenues. Through comprehensive exploration, it aims to equip readers with the knowledge to navigate the complexities of osteoporosis management effectively.
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What's The Direct Impact of Low Estrogen on Bones?
Estrogen's relationship with bone health has long been suspected due to the high prevalence of low bone density and osteoporosis in postmenopausal women. Indeed, an estimated 1 in 3 women have osteoporosis compared to 1 in 5 in men (26).
Furthermore, women who undergo early menopause (before age 45) have an increased risk for osteoporosis and associated fractures (5).
Research has established estrogen deficiency as the leading cause of osteoporosis in older women due to the critical role that estrogen plays in maintaining bone homeostasis. As estrogen levels decline, this homeostasis falters, increasing bone turnover and resorption, which results in net bone density losses (5).
Symptoms and Diagnosis of Osteoporosis
Osteoporosis is a skeletal disorder marked by decreased bone density, reduced bone strength, and heightened fracture risk. Osteoporosis-related fractures occur most commonly in the wrist, hip, and vertebrae. They can profoundly impact the quality of life and even increase mortality risk (26).
Osteoporosis is diagnosed via a dual-energy X-ray absorptiometry (DEXA) scan that assesses bone density. This scan provides a score comparing bone density to that of an average 30-year-old to evaluate for possible loss of bone density.
Scores of -1 or more are considered normal, whereas scores between -1 and -2.5 indicate osteopenia (the precursor to osteoporosis), and scores less than -2.5 indicate osteoporosis.
DEXA scans are recommended starting at age 65 as part of routine screening in women. Most cases of osteoporosis are found incidentally as part of this screening, though some symptoms can warrant earlier identification. These include:
- Loss in height of 1.5 inches or more, indicating probable vertebral collapse due to low bone density
- Decreased hand grip strength in older adults
- Fractures in people over the age of 50
- Jaw shrinkage resulting in gum recession and other dental issues
The Role of Estrogen in Bone Health
What Is Estrogen?
Estrogen is a sex hormone that is critical in women's reproductive health, having direct effects on menstrual cycle regulation, fertility, and the development of secondary sex characteristics in puberty.
Beyond reproduction, estrogen impacts bone homeostasis, brain health, cognitive function, cardiovascular health, and mood regulation in all genders.
Estrogen and Bone Metabolism
Healthy bone metabolism is influenced by the intricate balance of the cells that build bone, called osteoblasts, and the cells that break down and resorb bone, called osteoclasts. When osteoclast production outpaces osteoblast production, bone loss results.
Estrogen directly influences bone homeostasis through its ability to inhibit osteoclast formation, thus limiting bone resorption and breakdown. It also activates signals that initiate bone production and osteoblast maturation. When estrogen levels are healthy, these actions keep bone metabolism in check. However, osteoclast production is no longer inhibited when estrogen levels are deficient, and bone loss can result (5).
How Menopause Affects Bone Density
The Menopause Transition
During a woman's reproductive years, most estrogen comes from the ovaries. As women age, ovarian production naturally declines until it can no longer synthesize estrogen or progesterone, resulting in a cessation of menstrual cycles and estrogen deficiency (22).
This process, called menopause, generally occurs around the age of 50 in most women, though it can be experienced earlier in cases of primary ovarian insufficiency or surgically induced menopause.
Estrogen, Menopause, and Osteoporosis Risk
Although bone mineral density naturally starts to decline around the age of 40, the significant drop in estrogen experienced during menopause can accelerate this loss. Osteoclasts are no longer checked by estrogen, leading to enhanced bone breakdown. This process is the first phase of bone loss experienced in women and is directly related to estrogen deficiency due to menopause.
During the first 5-6 years around menopause, the average loss of bone density is 10%, with approximately 25% of women experiencing more significant losses of up to 20%. The second phase of bone loss, which men also experience, occurs 4-8 years later, resulting from the reduction of bone formation (22).
The compounding effects of increased bone resorption and decreased bone formation lead to the high prevalence of osteoporosis in women after menopause (2). One study showed that the rate of osteoporosis in older women doubles every 5 years, from 6.4% between the ages of 50-54 to 13.5% at age 55 and up to > 50% in women 85 and older.
Prevention and Management of Osteoporosis
Lifestyle Modifications
Beyond hormones, certain lifestyle factors play a key role in bone health and can help reduce overall risk for osteoporosis. These include:
- Alcohol intake and cigarette smoking: Two or more alcoholic drinks per day and cigarette smoking have both been linked to increased bone deterioration. Reducing or avoiding these substances can help delay bone loss (5).
- Diet: Nutrient deficiencies that result in underweight status and a reduced protein intake are associated with muscle and bone loss. Nutrient-dense foods and healthy protein levels are recommended to prevent osteoporosis (5).
- Vitamin D: Vitamin D plays a vital role in building healthy bones. For osteoporosis prevention, daily supplementation of 800-2000IU is recommended (5).
- Calcium: Calcium also supports healthy bone production. It is recommended that people consume at least 1200 mg of calcium daily, primarily from food, with some supplementation if needed (5).
- Exercise: Resistance training and weight-bearing exercises can positively affect bone health, increase muscle strength, and help enhance coordination and balance, all of which help decrease fracture risk by preventing falls (2).
Hormonal Medications and Treatments
Estrogen replacement therapy (ERT) is a popular and effective method of reducing osteoporosis and fracture risk in postmenopausal women. ERT increases circulating levels of estrogen in the body, allowing for proper inhibition of bone resorption and stimulation of bone formation, thus protecting against bone loss.
ERT has demonstrated efficacy in increasing bone density when initiated within 5 years of menopause onset, with bone density gains of 5.4% in the spine and 2.5% in the hip after just one year of therapy (22).
ERT is also effective in preventing fractures. In a study performed on perimenopausal women with low bone density, 6 years of ERT resulted in a 52% reduction in fracture risk. While promising, ERT is only found to be effective when started soon after menopause, ideally within the first 3-4 years. Additionally, once ERT is discontinued, bone loss resumes (22).
Beyond ERT, selective estrogen receptor modulators (SERMs) are a pharmaceutical treatment option for estrogen deficiency osteoporosis that can help increase estrogen production in select tissues. SERMS reduce the rate of vertebral fractures by 35%. However, it does not have a notable effect on hip fractures and can cause side effects such as hot flashes and calf cramps (26).
Estrogen Replacement Therapy: A Closer Look
What Is Estrogen Replacement Therapy?
ERT involves repleting deficient estrogen levels in the body through the use of estrogen products taken orally or applied topically. A medical provider prescribes ERT, most commonly for reducing menopausal symptoms like hot flashes, night sweats, and vaginal dryness.
Hormone replacement therapy (HRT) is similar to ERT except that it supplies progesterone and sometimes testosterone in addition to estrogen.
Pros and Cons of ERT
ERT is a safe and effective treatment of menopausal symptoms and associated osteoporosis when used appropriately and if initiated soon after menopause onset. However, if initiated after the age of 60 or later than 10 years after menopause, these benefits are reduced or disappear altogether, and the probability of harmful side effects increases (22).
Potential risks include increased incidence of stroke and blood clots with the use of oral estrogens and a slight risk of breast cancer with both oral and topical forms. Generally, it is recommended that the lowest effective dose of ERT be used when treating or preventing osteoporosis, and patients should be carefully monitored for potential side effects (22).
Alternative Treatments
Non-Hormonal Options for Osteoporosis
Besides ERT, bisphosphonates are commonly prescribed to treat osteoporosis. Bisphosphonates prevent bone resorption and are highly effective at reducing the risk of hip and vertebral fractures. However, they can cause gastrointestinal upset and may not be tolerated in patients with reflux and other stomach conditions.
Additionally, there is some controversy regarding the safety and efficacy of long-term bisphosphonate use, with reports of femoral fractures increasing over time (26).
Denosumab is often recommended as an alternative when bisphosphonates are not well tolerated. Denosumab is a monoclonal antibody administered via injection that inhibits osteoclast formation and reduces overall fracture risk (5).
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Key Takeaways
- Estrogen's crucial role in bone health, particularly in postmenopausal women, underscores its significance in combating osteoporosis.
- Its decline during menopause increases bone turnover and density loss, elevating fracture risk.
- Understanding estrogen's influence empowers individuals to adopt preventive measures and explore treatment options like ERT.
- By recognizing estrogen's pivotal role, we can better address osteoporosis and safeguard skeletal strength effectively.
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