What Causes Osteoporosis? Causes and Risk Factors Explained

What actually causes osteoporosis — and why do bones weaken silently?

Osteoporosis is caused by an imbalance in the way bone constantly renews itself. Throughout life your skeleton is broken down and rebuilt in a continuous cycle: cells called osteoclasts remove old bone, and osteoblasts lay down new bone. When removal starts to outpace replacement, bone density and internal structure are gradually lost, leaving bones thinner, more porous and more likely to break.

A 2024 review in Pharmaceuticals describes how, as this balance tips, bone resorption (breakdown) exceeds new bone formation — the core mechanism behind the condition (Pharmaceuticals, 2024). Because this happens slowly and without pain, osteoporosis is often called a silent disease: most people have no symptoms at all until a bone breaks, frequently after a minor fall or knock.

The scale of that silent burden is significant. The UK's 2024 NOGG clinical guideline estimates around 549,000 new fragility fractures each year in the UK, including roughly 105,000 hip fractures, at an NHS cost exceeding £4.7 billion per annum (NOGG 2024 UK guideline). The Royal Osteoporosis Society estimates that around 3.5 million people in the UK have osteoporosis (Royal Osteoporosis Society).

Why are women at higher risk, and does menopause always trigger bone loss?

Women are at higher risk largely because of the menopause. Oestrogen helps keep bone breakdown in check, so when oestrogen levels fall at menopause, the rate of bone loss accelerates. The Pharmaceuticals review explains that declining oestrogen activates osteoclasts, so resorption outpaces formation — which is why postmenopausal osteoporosis is the most common form (Pharmaceuticals, 2024). That same review groups osteoporosis into three primary subtypes: postmenopausal, senile (age-related) and idiopathic.

Some bone loss after menopause is normal, but the risk is higher for some women than others. The NHS highlights that an early menopause (before age 45), a hysterectomy before 45 — particularly if the ovaries are also removed — and absent periods for more than six months due to over-exercising or excessive dieting all increase risk (NHS). Internationally, the IOF estimates that 1 in 3 women and 1 in 5 men over 50 will experience an osteoporotic fracture (International Osteoporosis Foundation).

If you are navigating the menopause, our menopause and bone health guides go into more depth on protecting your skeleton through this transition.

Do men get osteoporosis, and why is it so often missed?

Yes — osteoporosis affects men too, and it is frequently missed. It is widely thought of as a women's condition, which means men are often not assessed until after they break a bone. The NHS notes that the risk of osteoporosis is increased in men with low levels of testosterone (NHS).

Research suggests that around one in five men will experience a fragility fracture at some point in their lifetime, and that men account for roughly 30% of all hip fractures — with worse outcomes afterwards than women in some studies (Int J Mol Sci, 2021). The same review reports US population data (NHANES, 2005–2008) in which osteoporosis prevalence was about 4% in men versus 16% in women — a useful illustration of the gap, though as US data it should not be read directly as a UK figure.

Crucially, secondary causes are especially common in men. A 2024 review reports that the prevalence of an underlying cause behind osteoporosis in men may be as high as 64%, and that secondary osteoporosis is frequently undiagnosed, particularly in premenopausal women and men (Biomedicines, 2024). That makes proactive assessment in men especially worthwhile.

Which medical conditions and medications can cause secondary osteoporosis?

Secondary osteoporosis is bone loss driven by another condition or a medication, rather than ageing or menopause alone — and it is common. The same 2024 review notes that around 30% of postmenopausal women with osteoporosis also have an underlying disorder contributing to it, and names chronic kidney disease, glucocorticoid (steroid) use and diabetes among the leading contributors (Biomedicines, 2024).

Long-term steroid tablets are the standout medication cause. The NHS lists steroid tablets among the medicines that can increase osteoporosis risk (NHS), and the Pharmaceuticals review notes that glucocorticoid-induced osteoporosis accounts for an estimated 30–50% of cases linked to medication (Pharmaceuticals, 2024). The picture from specialist sources is stark: in people on chronic steroid therapy, fractures occur in 30–50% of patients, and daily prednisone above 10 mg for more than 90 days has been associated with a seven-fold rise in hip fracture risk and a 17-fold rise in vertebral fracture risk — yet only an estimated 4–14% of long-term oral steroid users receive bone-protection treatment (Endotext / NCBI Bookshelf).

The UK NOGG guideline reflects this in its risk assessment, flagging high-dose oral glucocorticoids (≥7.5 mg/day prednisolone over three months) as a marker of very high fracture risk (NOGG 2024 UK guideline). Other treatments linked to bone loss in clinical practice include some hormone therapies used in breast and prostate cancer, certain anti-epileptic drugs, and long-term acid-suppressing medicines. You can read more about the conditions and medications that affect bone health in our wider guides.

Which risk factors for osteoporosis can you actually change?

Some causes are fixed — but several of the biggest risk factors are within your control. The UK NOGG guideline lists a set of validated clinical risk factors, including a previous fragility fracture, a parental history of hip fracture, low body mass index, smoking, alcohol intake of three or more units a day, oral glucocorticoid use, rheumatoid arthritis and diabetes (NOGG 2024 UK guideline).

Within that list, the factors you can influence include:

• Stopping smoking, which is directly harmful to bone.
• Keeping alcohol within recommended limits — heavier intake raises risk.
• Staying active with weight-bearing and resistance exercise to load and stimulate bone (and to protect muscle, which works hand in hand with bone).
• Eating well for bone. The British Dietetic Association advises an ideal daily calcium intake of around 700 mg for adults (up to 1,000 mg for those on osteoporosis drug treatment), that all adults should consider a daily 10 µg (400 IU) vitamin D supplement, especially in autumn and winter, and that adequate protein plus fruit and vegetables support bone health (British Dietetic Association). Aim to meet these needs through a balanced diet, with supplements where intake is insufficient.

Our nutrition and supplements guides cover calcium, vitamin D and protein in more detail.

Can younger people develop osteoporosis, and what causes it before menopause?

Yes — osteoporosis is not only a condition of older age. It can develop in younger adults, usually because of a secondary cause rather than simple ageing. The 2024 review on secondary causes highlights that osteoporosis is frequently undiagnosed in premenopausal women and men, precisely the groups least likely to be screened (Biomedicines, 2024).

In younger people, contributors can include long-term steroid use, conditions such as chronic kidney disease or diabetes, and hormonal disruption. The NHS specifically flags absent periods for more than six months as a result of over-exercising or too much dieting as a cause of bone loss — relevant to younger, very active women in particular (NHS). Because younger adults rarely fit the typical osteoporosis profile, the condition is easily overlooked until a fracture occurs — which makes baseline screening valuable for anyone with a known risk factor, regardless of age.

How do you find out if you are at risk before a fracture happens?

The only way to know your bone density before a fracture is to measure it. Osteoporosis is formally defined by a bone mineral density T-score of −2.5 or lower (NOGG 2024 UK guideline), and the only way to find that number is a scan — you cannot feel low bone density, and you will not see it coming.

A bone health assessment measures your bone density and combines it with your personal risk factors — age, family history, menopause status, medications and lifestyle — so you understand where you stand. If you already have one of the risk factors covered above, a baseline measurement is the practical first step.

Why a radiation-free REMS scan suits proactive, repeat screening

Screen My Bones uses REMS (Radiofrequency Echographic Multi Spectrometry), a radiation-free bone density technology. Because it uses no ionising radiation, a REMS scan can be repeated safely over time to track how your bone density is changing — useful if you are on a long-term medication, going through the menopause, or simply want to keep an eye on a known risk factor.

You can book a bone health assessment, explore our biodensity screening and full range of services, or see where we screen across the UK.

The bottom line on what causes osteoporosis

Osteoporosis is caused by bone being lost faster than it is replaced — a process driven mainly by ageing and the menopause, and accelerated in many people by medications such as steroids and by underlying medical conditions. Much of that risk is silent, and a meaningful share is preventable or treatable once it is known. The single most useful thing you can do is move from guessing to knowing: understand your risk factors and, if any apply to you, measure your bone density before a fracture forces the issue.

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This article is part of our bone health series. If you take weight-loss injections, see our guide on whether Ozempic and weight-loss medications cause bone loss; if you are going through the menopause, start with our menopause and bone health guides.