Bone Density and Menopause

Almost everything sold under the name “horny goat weed” is sold for sex. That is a marketing accident of a memorable English name, and it points readers away from the one thing this herb has actually been tested for in a proper human trial: bone loss after menopause.

The traditional indication points the same way. In Chinese medicine yin yang huo is a kidney-yang tonic used for “weak sinews and bones” and aching lower back and knees, and the kidney system in that framework governs bone. So tradition and modern research converge here in a way they do not for erectile function — which is worth noticing without over-reading.

This article covers what the human evidence actually is: one substantial trial, one small modern trial, a large preclinical literature, and a set of caveats that matter. The honest headline is that the bone evidence is better than the sexual-function evidence by a wide margin, and still not strong enough to treat osteoporosis with.

Table of Contents

1. Why Bone Is the Better Story
2. What Happens to Bone at Menopause
3. The 2007 Hong Kong Trial, in Detail
4. The Catch in That Trial
5. The 2021 Singapore Trial
6. The Mechanism: Selective Oestrogen-Receptor Activation
7. The Single-Country Problem
8. How This Compares With Proven Treatments
9. Who Should Not Take This
10. What to Do Instead, and Alongside
11. Key Research Papers
12. Connections

Why Bone Is the Better Story

Compare the two evidence bases directly.

A single 100-person trial is not a large evidence base. But it is an actual randomised, double-blind, placebo-controlled trial with an objective imaging endpoint and a two-year follow-up, published in the Journal of Bone and Mineral Research — the leading specialist journal in the field. That is a different universe from a rat study.

What Happens to Bone at Menopause

Bone is not inert scaffolding. It is a living tissue in permanent turnover, continually demolished and rebuilt by two cell types working in opposition:

• Osteoclasts dissolve old bone. They are the demolition crew.
• Osteoblasts lay down new bone matrix and mineralise it. They are the builders.

Oestrogen is the brake on the demolition crew. It restrains osteoclast formation and shortens osteoclast lifespan, largely through a signalling system called RANK–RANKL–osteoprotegerin. When oestrogen falls at menopause the brake comes off: osteoclasts become more numerous and more active, resorption outruns formation, and bone is lost. The loss is fastest in the first five to ten years after the final period and is heaviest in trabecular bone — the spongy, honeycomb interior found in the vertebrae, the hip and the wrist. That is why postmenopausal fractures cluster in exactly those three places.

Two numbers frame the stakes. A T-score is how many standard deviations your bone density sits from a healthy young adult; −1 to −2.5 is osteopenia and below −2.5 is osteoporosis. And a hip fracture in an older adult is not a broken bone in the ordinary sense — it is a life event, with a substantial one-year mortality and a high rate of permanent loss of independence. Anything that genuinely slows bone loss is worth taking seriously.

The 2007 Hong Kong Trial, in Detail

Zhang, Qin and Shi at the Department of Orthopaedics and Traumatology, Chinese University of Hong Kong, published this in 2007. It remains the most important human study of this herb.

What it found

Over 24 months the placebo group lost bone: −2.4 percent at the lumbar spine (p = 0.002) and −1.8 percent at the femoral neck (p = 0.048). The treatment group did not: +1.3 percent at the spine and +1.6 percent at the femoral neck. The difference between groups was statistically significant at both sites by 24 months — p = 0.006 at the spine and p = 0.008 at the femoral neck.

Read that carefully, because the phrasing matters. The gains inside the treatment group were not themselves statistically significant (p = 0.091 at the spine, p = 0.148 at the femoral neck). The between-group difference is real, but it is driven substantially by the placebo arm losing bone rather than by the treatment arm building it. The honest description is prevention of loss, not increase in density — which is still a worthwhile thing, and is what most osteoporosis prevention aims at.

The bone turnover markers tell a consistent story. Deoxypyridinoline, a marker of bone resorption, fell 43 percent at 12 months and 39 percent at 24 months in the treatment group and did not move in placebo. Osteocalcin, a marker of bone formation, rose only slightly and not significantly (+5.6 percent, then +10.7 percent; both non-significant). So the preparation behaved like an antiresorptive — it slowed demolition rather than accelerating building.

One genuinely reassuring finding: neither serum oestradiol nor endometrial thickness changed in either group over two years. For a preparation described as phyto-oestrogenic, the absence of endometrial thickening is a real safety signal and the authors highlighted it.

The Catch in That Trial

Four caveats, in descending order of importance.

1. The product was not Epimedium alone

This is the big one. The daily dose was 60 mg icariin plus 15 mg daidzein plus 3 mg genistein. Icariin is the Epimedium marker. Daidzein and genistein are the classic soy isoflavones — the compounds behind the entire soy-and-bone literature, and phyto-oestrogens in their own right with their own trials in postmenopausal women.

The published abstract does not state whether those two isoflavones were extracted from the Epimedium material or added to the formulation. Either way the consequence is the same: the trial tested a three-compound phyto-oestrogen blend, and cannot tell you what icariin contributed on its own. A supplement containing only Epimedium leaf is not the product that was studied, and neither is a capsule standardised to icariin alone.

2. The calcium background was thin, and there was no vitamin D

Both arms received 300 mg of elemental calcium daily. Modern osteoporosis prevention targets a total calcium intake around 1,000–1,200 mg per day, usually with 800 IU or more of vitamin D. No vitamin D was given here at all.

That matters because a placebo group that is under-supported will lose bone faster, which widens the gap the treatment has to beat. It does not invalidate the result — both arms were treated identically, which is what randomisation is for — but it means the 3–4 percentage-point separation may look larger than it would against an adequately supplemented control.

3. BMD is a surrogate, not the outcome anyone cares about

Nobody suffers from a low DXA number. People suffer from fractures. BMD correlates with fracture risk but the relationship is loose, and drugs have repeatedly changed BMD without changing fractures in the expected proportion. This trial measured no fractures, and with 85 completers over two years in women with osteopenia it could not have. There is no fracture evidence for Epimedium at all.

4. One trial is one trial

It has not been independently replicated with BMD endpoints by another group, in another country, in the eighteen years since publication. For a positive, well-published finding in a common condition, that absence is conspicuous.

The 2021 Singapore Trial

The most methodologically careful human study of Epimedium is more recent and much shorter. A team at the National University of Singapore randomised 58 healthy postmenopausal women, mean age 57.9, to a purified Epimedium prenylflavonoid extract at 740 mg per day or placebo, double-blind, for six weeks, recruiting between October 2018 and June 2020.

Its primary aims were safety and pharmacokinetics, not efficacy, and it delivered on both:

• Safety. No significant adverse symptoms. No changes in liver, kidney or blood parameters over six weeks. For a herb with liver-injury reports attached to it, a clean panel in a monitored trial is worth having, though six weeks is short.
• Pharmacokinetics. The metabolites reaching serum were desmethylicaritin, icaritin and icariside II. Icariin and icariside I were below detection. Median peak desmethylicaritin was 60.9 nM. No prenylflavonoid metabolites appeared in placebo participants, confirming the assay was measuring what it claimed to.
• Biomarkers. Bone-specific alkaline phosphatase, a marker of bone formation, was higher in the treatment group (p < 0.05). TRAF6, an adaptor protein in osteoclast precursors, showed a non-significant downward trend (p = 0.068).

Two things to take from this. First, the pharmacokinetic result is the most important single measurement anyone has made on this herb, and it is the backbone of the argument on the sexual-function page. Second, and more subtly: the 2021 trial found a rise in a formation marker, while the 2007 trial found a fall in a resorption marker with no formation change. Those point at different mechanisms. The authors themselves wrote that despite widespread consumption, “the safety, mechanisms of action of their bioactive compounds, and therapeutic indications in humans are unknown.” That is the field’s own assessment, from the group most invested in it.

The Mechanism: Selective Oestrogen-Receptor Activation

The preclinical work gives a coherent explanation, and it also explains the main safety caution.

Epimedium flavonoids selectively activate oestrogen receptor alpha (ERα) and switch on oestrogen-dependent osteoblast functions in bone cells. That selectivity is the interesting part. Oestrogen receptors come in two main flavours, ERα and ERβ, distributed differently across tissues, and a compound that engages one preferentially can in principle act like oestrogen in bone without acting like oestrogen everywhere — the same logic behind pharmaceutical selective oestrogen receptor modulators such as raloxifene.

Layered on top, animal and cell work reports that icariin and its metabolites push the osteoblast–osteoclast balance toward building: encouraging osteoblast differentiation, discouraging osteoclast formation, and modulating RANKL signalling. Reviews of this literature describe it as broadly consistent across models.

Two honest riders. Preclinical consistency is a weak predictor of clinical benefit — the osteoporosis field is littered with compounds that worked beautifully in ovariectomised rats and did nothing in women. And oestrogen-receptor activity is exactly why this herb is not benign for everyone, which is the next section.

The Single-Country Problem

Almost the entire Epimedium bone literature comes from one region. The 2007 trial: Hong Kong. The 2021 trial: Singapore. The great majority of the cell and animal work, and essentially all of the meta-analyses of Chinese herbal formulas containing Epimedium: mainland China.

This is not an accusation of bad faith. Herbs get studied where they are used, and Chinese institutions have invested seriously and produced work in first-tier international journals. But two structural facts follow, and both are relevant to a reader deciding what to believe.

First, independent replication has essentially not happened. No European or North American group has run a BMD trial of Epimedium. When a finding is only ever produced by researchers working in one tradition and one regulatory environment, the usual cross-checks that catch errors have not run.

Second, the two most rigorous non-mainland contributions — the 2016 Pharmacology & Therapeutics review and the 2021 Singapore trial — share a senior author. They are the products of one research programme, not two independent lines of evidence. That programme has been careful and appropriately sceptical, which is to its credit. It is still one programme.

How This Compares With Proven Treatments

Perspective matters here, because women are sometimes offered this herb as an alternative to medication.

Bisphosphonates such as alendronate and zoledronic acid, and the RANKL antibody denosumab, produce substantially larger increases in bone mineral density than the 2–4 percentage-point separation seen with the Epimedium blend — and, far more importantly, they have been shown in randomised trials enrolling tens of thousands of participants to reduce actual fractures at the spine and hip. Menopausal hormone therapy also reduces fractures and, when started near the menopause in appropriate candidates, carries a risk–benefit profile that has been re-evaluated more favourably in recent years. Anabolic agents such as teriparatide and romosozumab build bone outright.

Every one of those has been tested against the endpoint that matters. Epimedium has been tested against a DXA number, once.

Where a botanical could reasonably fit is at the mild end: a woman with osteopenia, not osteoporosis, not yet a candidate for drug therapy, who is already doing the fundamentals and wants to add something. That is precisely the population the 2007 trial enrolled — T-scores between −2 and −2.5. It is not a substitute for treatment in someone with established osteoporosis or a prior fragility fracture, and framing it as one would be a serious error.

Who Should Not Take This

• Anyone with a hormone-sensitive condition. Oestrogen-receptor-positive breast cancer (current or past), endometrial cancer, ovarian cancer, endometriosis, uterine fibroids. Epimedium flavonoids activate ERα. The 2007 trial found no endometrial thickening over two years, which is reassuring for healthy women, but it enrolled healthy women — it says nothing about someone with an oestrogen-driven tumour.
• Anyone taking tamoxifen or an aromatase inhibitor. Adding a phyto-oestrogen to endocrine therapy is a theoretical antagonism nobody has studied. Do not do this without oncology input.
• Pregnancy and breastfeeding. No data, clear hormonal activity. Avoid.
• Existing liver disease. Liver injury is the most commonly reported adverse effect of Epimedium in the Chinese literature.
• Anticoagulant or antihypertensive therapy. Interaction data are sparse. Sparse is not the same as safe. Ask a pharmacist.
• Anyone with a cardiac arrhythmia. A case report describes tachyarrhythmia associated with this herb.

What to Do Instead, and Alongside

If bone is the actual concern, these are the things with the strongest evidence, and they cost less than the supplement:

1. Get a DXA scan. You cannot manage a number you have never measured. Know your T-score at spine and hip. Ask about a FRAX 10-year fracture risk estimate.
2. Hit calcium and vitamin D targets — from food first. Roughly 1,000–1,200 mg calcium daily for postmenopausal women, ideally from dairy, tinned fish with bones, tofu set with calcium, and fortified foods. Vitamin D sufficiency matters as much as the calcium itself; get a level checked if you are indoors, covered, or dark-skinned at high latitude.
3. Load the skeleton. Bone responds to mechanical strain. Progressive resistance training and impact activity build and preserve bone; walking alone largely does not. Two to three sessions a week that get genuinely heavy is the intervention with the best evidence available to a healthy person.
4. Protein. Adequate dietary protein supports both bone matrix and the muscle that protects you in a fall.
5. Remove the accelerants. Smoking, heavy alcohol, and where clinically possible long-term proton pump inhibitors and oral corticosteroids.
6. Prevent falls. Balance training, vision checks, a medication review for anything sedating, and the boring domestic work of rugs, cords, lighting and stairs. Most fragility fractures require a fall as well as fragile bone.
7. Discuss drug therapy honestly if your T-score is below −2.5 or you have had a fragility fracture. This is where the fracture-reducing evidence lives.

If, after all that, you want to add Epimedium at the osteopenia stage — that is a defensible choice, made with open eyes. Buy a product that names a species and states its icariin content in milligrams, tell your doctor, and understand that you are betting on one 100-person trial of a blend rather than on established therapy.

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Key Research Papers

Each identifier below was verified live against NCBI E-utilities — first author, title, journal and year all had to match.

Human trials

1. Zhang G, Qin L, Shi Y. Epimedium-derived phytoestrogen flavonoids exert beneficial effect on preventing bone loss in late postmenopausal women: a 24-month randomized, double-blind and placebo-controlled trial. Journal of Bone and Mineral Research. 2007;22(7):1072–1079. The trial described in detail above — note the daidzein and genistein content of the tested preparation.
2. Yong EL, Cheong WF, Huang Z, Thu WPP, Cazenave-Gassiot A, Seng KY, Logan S. Randomized, double-blind, placebo-controlled trial to examine the safety, pharmacokinetics and effects of Epimedium prenylflavonoids, on bone specific alkaline phosphatase and the osteoclast adaptor protein TRAF6 in post-menopausal women. Phytomedicine. 2021;91:153680. Six weeks, n=58, Singapore; safe over that period, icariin undetectable in serum.
3. Lin WL, et al. Benefits of herbal medicine on bone mineral density in osteoporosis: a meta-analysis of randomized controlled trials. The American Journal of Chinese Medicine. 2020;48(8):1749–1768. Pools herbal interventions broadly rather than Epimedium specifically — useful context, not a per-herb answer.

Reviews of the bone evidence

1. Indran IR, Liang RLZ, Min TE, Yong EL. Preclinical studies and clinical evaluation of compounds from the genus Epimedium for osteoporosis and bone health. Pharmacology & Therapeutics. 2016;162:188–205. The most careful appraisal of this literature; weighs the preclinical enthusiasm against the thin clinical record.
2. Wang Z, et al. The effect of icariin on bone metabolism and its potential clinical application. Osteoporosis International. 2018;29(3):535–544.

Mechanism

1. Xiao HH, et al. Flavonoids from Herba epimedii selectively activate estrogen receptor alpha (ERα) and stimulate ER-dependent osteoblastic functions in UMR-106 cells. Journal of Steroid Biochemistry and Molecular Biology. 2014;143:141–151. Cell culture — the ERα selectivity that explains both the bone effect and the hormone-sensitivity caution.
2. Li C, Li Q, Mei Q, Lu T. Pharmacological effects and pharmacokinetic properties of icariin, the major bioactive component in Herba Epimedii. Life Sciences. 2015;126:57–68.
3. Ma H, He X, Yang Y, et al. The genus Epimedium: an ethnopharmacological and phytochemical review. Journal of Ethnopharmacology. 2011;134(3):519–541.

Safety relevant to this use

1. Wang J, Cao Y, Sun M, et al. Integrating metabolomics and bioinformatics to reveal the mechanism of Epimedium-induced liver injury. Biomedical Chromatography. 2024;38(9):e5948.
2. Qian HQ, et al. A systematic review of traditional uses, phytochemistry, pharmacology and toxicity of Epimedium koreanum Nakai. Journal of Ethnopharmacology. 2024;318(Pt B):116957.

Live PubMed Searches

1. Epimedium and osteoporosis
2. Icariin, osteoblasts and osteoclasts
3. Epimedium and bone mineral density trials
4. Phyto-oestrogens and postmenopausal bone
5. Genistein and daidzein bone trials
6. Resistance training and postmenopausal bone
7. Bisphosphonates and fracture reduction
8. Deoxypyridinoline as a resorption marker

Connections

• All Herbs
• Epimedium Benefits — hub
• Epimedium (Horny Goat Weed)
• Safety, Adulteration and Product Quality
• Traditional Use in Chinese Medicine
• Osteoporosis
• Menopause
• Maca
• Cardiology

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