Hormone Replacement Therapy for Postmenopausal Osteoporosis

Madhusmita Misra, MD, MPH


September 21, 2023

The actress Sally Field recently described her struggles with postmenopausal osteoporosis — she was given the diagnosis when she was 60 years old despite being physically active and engaging in activities such as biking, hiking, and yoga. As a slim, White woman in her sixth decade of life, she certainly had several risk factors for osteoporosis.

Madhusmita Misra, MD, MPH

Osteoporosis, a condition associated with weak bones and an increased risk for fracture, is common in women after menopause. It's defined as a bone mineral density (BMD) T-score ≤ -2.5 on dual-energy x-ray absorptiometry (DXA) scan, or occurrence of a spine or hip fracture regardless of BMD, or a BMD T-score between -1 and -2.5, along with a history of certain kinds of fractures or increased fracture risk based on the Fracture Risk Assessment Tool (FRAX).

The National Health and Nutrition Examination Survey from 2013 to 2014 reported that 16.5 % of women aged 50 years or older in the US have osteoporosis (vs only 5% of men of a similar age), with an increasing prevalence with increasing age. For example, the risk for osteoporosis of the hip increases from about 7% in women 50-59 years of age to about 35% in those aged 80 years or older. The risk for postmenopausal osteoporosis is reported to be highest in Asian women (40%), followed by Hispanic (20.5%), non-Hispanic White (17%), and non-Hispanic Black women (8.2%).

Why Increased Fracture Risk in Postmenopausal Women?

The primary cause of postmenopausal osteoporosis is the cessation of estrogen production by the ovaries around the menopausal transition. Estrogen is very important for bone health. It reduces bone loss by reducing levels of receptor activator of NF-kappa B ligand (RANKL) and sclerostin, and it probably also increases bone formation through its effects on sclerostin.

Around menopause, the decrease in estrogen levels results in an increase in RANKL and sclerostin, with a consequent increase in bone loss at a pace that exceeds the rate of bone formation, thereby leading to osteoporosis.

Many factors further increase the risk for osteoporosis and fracture in postmenopausal women. These include a sedentary lifestyle, lower body weight, family history of osteoporosis, smoking, and certain medications and diseases. Medications that adversely affect bone health at this age include (but are not limited to) glucocorticoids such as hydrocortisone, prednisone and dexamethasone, letrozole, excess thyroid hormone, certain drugs used to treat cancer, immunosuppressive drugs, certain antiseizure medications, proton pump inhibitors (such as omeprazole), sodium-glucose cotransporter 2 inhibitors and certain other drugs used to treat type 2 diabetes, and selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors (used to treat anxiety and depression).

Diseases associated with increased osteoporosis risk include certain genetic conditions affecting bone, a history of early ovarian insufficiency, hyperthyroidism, high levels of cortisol, diabetes, hyperparathyroidism, eating disorders, obesity, calcium and vitamin D deficiency, excess urinary excretion of calcium, malabsorption and certain gastrointestinal surgeries, chronic kidney disease, rheumatoid arthritis, certain types of cancer, and frailty.

Furthermore, older age, low bone density, a previous history of fracture, a family history of hip fracture, smoking, and excessive alcohol intake increase the risk for an osteoporotic fracture in a postmenopausal woman.

Bone density assessment using DXA is recommended in postmenopausal women who are at increased risk for low bone density and fracture. Monitoring of bone density is typically initiated about 5 years after the menopausal transition but should be considered earlier in those at high risk for osteoporosis. Women who are aged 70 or older, and those who have had significant height loss, should also get radiography of the spine to look for vertebral fractures.

Optimal nutrition is important for all postmenopausal women. Weight extremes are to be avoided. Although the use of calcium and vitamin D supplementation in postmenopausal women is still debated, the Institute of Medicine recommends that women 51-70 years of age take 1000-1200 mg of calcium and 400-600 IU of vitamin D daily, and that those older than 70 years take 1000-1200 mg of calcium and 400-800 IU of vitamin D daily.

Women with low vitamin D levels often require higher doses of vitamin D. It's very important to avoid smoking and excessive alcohol consumption. Optimizing protein intake and exercises that improve muscle strength and improve balance can reduce the risk for falls, a key contributor to osteoporotic fractures.

Estrogen to Prevent Fracture Risk

Because estrogen deficiency is a key cause of postmenopausal osteoporosis, estrogen replacement therapy has been used to prevent this condition, particularly early in the menopausal transition (51-60 years). Different formulations of estrogen given via oral or transdermal routes have been demonstrated to prevent osteoporosis; transdermal estrogen is often preferred because of a lower risk for blood clots and stroke. Women who have an intact uterus should also receive a progestin preparation either daily or cyclically, because estrogen alone can increase the risk for uterine cancer in the long run. Estrogen replacement has been associated with a 34% reduction in vertebral, hip, and total fractures in women of this age group.

Sally Field did receive hormone replacement therapy, which was helpful for her bones. However, as typically happens, her bone density dropped again when she discontinued hormone replacement. She also had low vitamin D levels, but vitamin D supplementation was not helpful. She received other medical intervention, with recovery back to good bone health.

Raloxifene is a medication that acts on the estrogen receptor, with beneficial effects on bone, and is approved for prevention and treatment of postmenopausal osteoporosis.

Medications that reduce bone loss (antiresorptive drugs), such as bisphosphonates and denosumab, and those that increase bone formation (osteoanabolic drugs), such as teriparatide, abaloparatide, and romosozumab, are used alone or in combination in women whose osteoporosis doesn't respond to lifestyle and preventive strategies. The osteoanabolic drugs are typically reserved for women at very high risk for fractures, such as those with a BMD T-score ≤ -3, older women with recent fractures, and those with other risk factors. Treatment is typically lifelong.

Postmenopausal osteoporosis can have far-reaching consequences on one's quality of life, given the risk for fractures that are often associated with hospitalization, surgery, and long periods of rehabilitation (such as fractures of the spine and hip). It's important to recognize those at greatest risk for this condition; implement bone health monitoring in a timely fashion; and ensure optimal nutrition, calcium and vitamin D supplementation, and exercises that optimize muscle strength and balance. Hormone replacement therapy is a consideration in many women. Some women will require antiresorptive or osteoanabolic drugs to manage this condition. With optimal treatment, older women can now live long and productive lives.

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