Osteoporosis develops when bones lose enough density and strength that they become more likely to fracture. For some people, this happens mainly because of ageing and hormonal changes after menopause. For others, osteoporosis develops partly because of another medical condition or a medicine that accelerates bone loss.
The good news is that osteoporosis can often be treated effectively. Treatment may include:
- Correcting calcium or vitamin D deficiency
- Weight-bearing and muscle-strengthening exercise
- Reducing fall risk
- Treating an underlying medical cause
- Medicines that slow bone loss
- Medicines that actively stimulate new bone formation in people at very high fracture risk
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
The most appropriate treatment depends not simply on a bone-density number, but on the person's overall risk of breaking a bone. For a broader overview of diagnosis and available therapies, see our main guide to Osteoporosis Treatment.
What Actually Causes Osteoporosis?
Bone may look solid and permanent, but it is living tissue that is constantly being renewed. Throughout life, two important processes occur:
- Bone resorption: old or damaged bone is broken down
- Bone formation: new bone is produced to replace it
In healthy younger adults, these processes are generally well balanced. With ageing and certain medical conditions, however, bone may be broken down faster than it can be replaced. Over time, bones become:
- Less dense
- More porous
- Structurally weaker
- More vulnerable to fractures
Primary vs Secondary Osteoporosis
It is useful to divide the causes into two broad groups.
| Type | Main Explanation | Common Examples |
|---|---|---|
| Primary osteoporosis | Bone loss mainly related to ageing and hormonal changes | Postmenopausal osteoporosis and age-related osteoporosis |
| Secondary osteoporosis | Bone loss caused or accelerated by another condition or medication | Long-term steroid use, hormonal disorders, malabsorption and certain chronic diseases |
1. Ageing
Age is one of the strongest osteoporosis risk factors. As people grow older:
- Bone formation becomes slower
- Bone resorption may exceed bone replacement
- Muscle strength may decline
- Falls become more likely
The combination of weaker bone and increased fall risk makes fractures more common with advancing age. Osteoporosis affects both women and men, although women generally develop it earlier and more frequently.
2. Menopause and Low Estrogen
One of the most important causes of osteoporosis in women is the fall in estrogen around menopause. Estrogen helps regulate bone turnover. When estrogen levels fall, bone resorption accelerates and women can lose bone more rapidly, particularly during the years around and immediately after menopause.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Risk can be especially important in women who:
- Experience menopause early
- Have their ovaries removed before natural menopause
- Have prolonged periods of very low estrogen
3. Low Testosterone and Other Hormonal Problems in Men
Men can also develop osteoporosis. Low testosterone or other conditions that reduce sex hormone levels may contribute to bone loss. This can occur because of:
- Hormonal disorders
- Certain cancer treatments
- Some pituitary or testicular conditions
Men receiving androgen-deprivation therapy for prostate cancer require particular attention to bone health because the treatment can accelerate bone loss.
4. Thyroid and Parathyroid Disorders
Certain hormone disorders can accelerate bone loss. Examples include:
- Overactive thyroid disease
- Excessive thyroid-hormone replacement
- Primary hyperparathyroidism
- Cushing syndrome or prolonged excess cortisol
5. Calcium and Vitamin D Deficiency
Calcium is an important structural component of bone, while vitamin D helps the body absorb calcium and supports normal bone mineralisation. Long-term inadequate intake or poor absorption can contribute to poor bone health. Vitamin D deficiency is particularly common in people who:
- Have little sunlight exposure
- Have certain intestinal or malabsorption disorders
- Have poor dietary intake
- Are older and housebound
6. Cancer Treatments
Some cancer treatments lower sex hormone levels and can accelerate bone loss. Examples include:
- Aromatase inhibitors used in some breast cancers
- Androgen-deprivation therapy used for prostate cancer
Can Osteoporosis Develop Without an Obvious Cause?
Yes. Some people have several recognisable risk factors, while others have no obvious explanation beyond ageing or hormonal changes. This is why doctors usually investigate for secondary causes when osteoporosis or a fragility fracture is diagnosed. The goal is to avoid treating low bone density while missing a medical problem that is continuing to weaken the skeleton.
How Do Doctors Find the Cause of Osteoporosis?
Assessment usually begins with a detailed medical history. The doctor may ask about:
- Previous fractures
- Family history of osteoporosis or hip fracture
- Menopause history
- Long-term steroid use
- Other medicines
- Thyroid or hormonal disorders
- Digestive symptoms
- Smoking and alcohol
- Diet and physical activity
DXA Bone-Density Scan
A DXA or DEXA scan is the standard test used to measure bone mineral density, usually at the hip and spine. For postmenopausal women and men aged 50 and older, a T-score of -2.5 or below at an appropriate skeletal site falls within the bone-density definition of osteoporosis. However, treatment decisions should not depend on T-score alone.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Fracture-Risk Assessment
Tools such as FRAX estimate the probability of major osteoporotic and hip fractures by combining clinical risk factors, with or without bone-density measurements. A person who has already experienced a fragility fracture may be at high risk even if their DXA result is not extremely low.
Blood Tests
People with osteoporosis or a fragility fracture may also undergo blood tests to look for underlying causes. Depending on the clinical situation, testing may assess areas such as:
- Calcium
- Vitamin D
- Kidney function
- Liver function
- Thyroid function
- Parathyroid hormone
- Other tests for secondary causes when indicated
7. Bone-Building Treatment for Very High Fracture Risk
Some people have such a high risk of fractures that starting with a medicine that builds new bone may be more appropriate than starting with an antiresorptive medicine. This group may include selected patients with:
- Multiple vertebral fractures
- A recent serious vertebral fracture
- Very low bone density
- Other features indicating very high fracture risk
8. Hormone Replacement Therapy
Hormone replacement therapy (HRT) can reduce bone loss and fracture risk in selected postmenopausal women. It may be particularly relevant to some younger postmenopausal women who:
- Have menopausal symptoms
- Have increased fracture risk
- Do not have important contraindications
Which Osteoporosis Treatment Is Best?
| Clinical Situation | Possible Treatment Direction |
|---|---|
| High fracture risk | Bisphosphonate commonly considered first-line |
| Oral bisphosphonate unsuitable | IV bisphosphonate, denosumab or another appropriate treatment may be considered |
| Very high fracture risk or multiple vertebral fractures | Specialist assessment for anabolic treatment may be appropriate |
| Osteoporosis caused by another disease | Treat the underlying condition plus address fracture risk |
| Glucocorticoid-induced osteoporosis | Assess fracture risk early and consider bone-protective therapy |
| Younger postmenopausal woman with suitable risk profile | HRT may be considered in selected cases |
Can Osteoporosis Be Reversed?
Bone density can improve with effective treatment, and fracture risk can be reduced substantially. Bone-building medicines can produce particularly meaningful increases in bone density in selected high-risk patients.
However, osteoporosis is generally managed as a long-term condition rather than described as permanently cured. A previous vertebral collapse or hip fracture cannot simply be undone by increasing bone density. The main aim is to:
- Strengthen remaining bone
- Prevent additional bone loss
- Reduce future fractures
- Maintain mobility and independence
Why Treatment After the First Fracture Matters
A previous fragility fracture is one of the strongest predictors of another fracture. The risk of a second fracture can be particularly high during the first few years after the first one.
This is why a hip, spinal, wrist or other low-trauma fracture in an older adult should trigger consideration of osteoporosis rather than being viewed only as an isolated injury. Current guidelines place particular emphasis on treating people who have already experienced a recent fragility fracture.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
The Bottom Line
Osteoporosis develops when bone is lost faster than it can be replaced, causing the skeleton to become weaker and more vulnerable to fractures.
Ageing and the loss of estrogen after menopause are major causes, but osteoporosis can also result from low hormone levels, long-term steroid treatment, thyroid or parathyroid disease, malabsorption, chronic inflammatory disorders, cancer treatments, poor nutrition and certain medications. This is why identifying the cause matters.
When another disease or medicine is contributing to bone loss, treating or managing that factor should form part of the osteoporosis plan. Lifestyle measures—including adequate calcium and vitamin D, appropriate exercise, smoking cessation and fall prevention—are important for everyone, but people at high fracture risk usually need osteoporosis medication as well.
Most importantly: Osteoporosis treatment is not simply about improving a bone-density score. The real objective is to identify why the bones became weak, correct reversible causes and choose a treatment strategy that meaningfully reduces the person's risk of a future fracture.
