HRT for osteoporosis: what estrogen does for your bones, and what happens when you stop

Hot flashes get most of the attention in menopause, but your bones are changing quietly too. Many women first hear the word osteoporosis after a bone density scan or a fracture, and wonder whether hormone therapy could have helped. This guide explains what estrogen does for bone, what the largest trials found, what HRT is and is not approved for, and what happens when you stop.

Why bone loss speeds up after menopause

Bone is living tissue. Throughout your life, your body breaks down old bone and builds new bone. Bone loss happens when more old bone is broken down than new bone is made ^[8]. A drop in estrogen at menopause is one of the causes of bone loss in women ^[8].

The Menopause Society explains that menopause increases bone breakdown, which doctors call resorption, and that estrogen therapy decreases it ^[1]. Osteoporosis is the result when bones become fragile and more likely to break ^[8]. Other risk factors include a family history of osteoporosis, low body weight, smoking, and heavy drinking ^[8].

Bone loss usually has no symptoms. The standard test is a DXA scan, a low-radiation x-ray of the hip and spine ^{[7, 8]}. MedlinePlus notes that the US Preventive Services Task Force recommends screening at least once for women 65 and older, and for some younger women at higher risk ^[8].

What the Women's Health Initiative found

The Women's Health Initiative (WHI) is the largest randomized trial of hormone therapy. Women were enrolled without regard to bone density or fracture risk, so most did not have osteoporosis ^[1]. That makes it a test of prevention.

Estrogen plus progestin

In the trial for women with a uterus, 16,608 women aged 50 to 79 took either a daily estrogen-plus-progestin pill or a placebo for an average of 5.6 years ^[2]. Fewer women on hormones had a fracture: 8.6% compared with 11.1% on placebo ^[2]. In a subgroup that had scans, total hip bone density rose 3.7% over three years on hormones, compared with 0.14% on placebo ^[2]. The fracture benefit was seen across every subgroup the researchers examined, including by age, weight, and fracture history ^[2].

Estrogen alone

In the trial for women who had a hysterectomy, 10,739 women took estrogen alone or a placebo for an average of about 7 years ^[3]. Estrogen alone lowered the risk of hip, spine, wrist, and total fractures, and modestly raised bone density ^[3]. The effect held regardless of age, whether the ovaries had been removed, or past fracture history ^[3]. Read more about this trial in HRT after hysterectomy.

In absolute numbers

The Menopause Society summarizes the WHI this way: in each trial, women on hormones had about six fewer hip fractures and six fewer spine fractures per 10,000 women compared with placebo ^[1]. A meta-analysis and systematic review, based mainly on the WHI, found that 5 to 7 years of hormone therapy significantly reduced spine, hip, and other fractures ^[1].

There is a nuance. In women who were 50 to 59 when they started, neither WHI trial showed a lower risk of hip fracture ^[1]. The Menopause Society says this may be partly because younger women without osteoporosis had a low risk of hip fracture to begin with ^[1].

Prevention, not treatment: what the FDA approves

This distinction trips up a lot of women. Hormone therapy is FDA-approved to prevent postmenopausal osteoporosis. It does not carry an FDA indication to treat osteoporosis, because randomized trials have not shown that it reduces fractures in women who already have osteoporosis ^[1]. The Menopause Society says non-estrogen medicines are preferred for treating existing osteoporosis ^[1].

Even for prevention, labels set limits. The Climara patch label says that when prescribing only to prevent osteoporosis, non-estrogen medicines should be considered first, and estrogen considered only for women at significant risk ^[5]. The estradiol tablet label says the same ^[6]. The NIH's National Institute of Arthritis and Musculoskeletal and Skin Diseases also notes that estrogen and hormone therapy are approved to prevent osteoporosis, and that women should weigh the risks and benefits carefully ^[7].

The Menopause Society adds that decisions about starting and stopping hormone therapy should be made mainly on the basis of benefits and risks beyond the bones, like relief of hot flashes ^[1]. In other words, bone protection is usually a welcome extra rather than the reason to start. For the full risk picture, see is HRT safe?

Doses used for bone

Some FDA-approved estradiol products list osteoporosis prevention among their uses. The Climara patch label starts at 0.025 mg per day for this purpose ^[5]. In a two-year trial on that label, 175 women who had a hysterectomy and did not have osteoporosis wore estradiol or placebo patches; bone density was preserved on every estradiol dose, while women on placebo lost bone ^[5]. For tablets, the label describes a study in which 0.5 mg a day for 23 days of each 28-day cycle prevented bone loss in the spine, and notes that the lowest effective dose for bone has not been determined ^[6].

The Menopause Society notes that hormone therapy's effect on bone density depends on dose ^[1]. Younger women with early menopause may need higher doses to protect bone ^[1]. Your clinician sets your dose; see our guide to estradiol dosage for how that works.

What happens to your bones when you stop

Estrogen's protection lasts only as long as you take it. The Menopause Society reports that within a few months of stopping, markers of bone turnover return to where they were before treatment, and bone density falls back to pre-treatment levels within one to two years ^[1]. The estradiol tablet label says bone mass declines after stopping at a rate similar to the years right after menopause ^[6].

That sounds alarming, but the fracture data are more reassuring. Researchers followed 15,187 WHI participants for five years after they stopped hormones or placebo ^[4]. Former hormone users did not have a higher fracture risk than former placebo users, either short-term or long-term ^[4]. Women who had taken estrogen alone even kept a small advantage for total fractures ^[4].

If you are planning to stop, talk with your clinician about your bone health first. They may suggest a bone density scan or another plan to protect your bones, especially if you have other risk factors.

Habits that matter with or without HRT

Medicine is only part of bone health. The NIH and the estradiol label both point to everyday steps ^{[6, 7]}:

• Strength or resistance training. Research suggests these are among the best activities for bone health. If you already have osteoporosis, avoid high-impact exercise ^[7].
• Weight-bearing activity, like walking ^[6].
• Calcium and vitamin D, from food or, if your intake falls short, supplements your clinician recommends ^{[6, 7]}.
• Fall prevention, such as good lighting, rails on stairs, and supportive, nonslip shoes ^[7].

Hormone therapy at WarriorBabe Health

WarriorBabe Health treats menopause symptoms with options including an estradiol patch and an oral estradiol tablet, paired with a progesterone capsule for women who have a uterus. Your clinician reviews your history, including your bone health, before prescribing. If you already have osteoporosis, ask about treatments made for it, since non-estrogen medicines are preferred there ^[1]. Compare options on our hormone treatments page.

Our products are compounded by a licensed pharmacy. Compounded drugs are not FDA-approved, and the FDA does not review their safety, effectiveness, or quality before they are marketed ^[9]. The FDA osteoporosis-prevention indication described here belongs to specific FDA-approved products and does not extend to compounded hormones ^[9]. To see whether hormone therapy might suit your symptoms, take the 2-minute quiz.

This article is for general information. It is not medical advice and does not replace a visit with a licensed clinician who knows your history. Do not start, stop or change a medication without talking to your clinician. If you think you are having a medical emergency, call 911.