What is the cause of osteoporosis?

What is osteoporosis?

Osteoporosis is a disease that causes bones to become weak and brittle. In osteoporosis, bone mineral density and bone mass decrease, or the bone’s structure changes, which makes fractures (broken bones) more likely.¹ Healthy bones are strong and somewhat dense, but osteoporotic bones are porous (less dense) and fragile. Because bone loss happens gradually and without symptoms, osteoporosis may not be noticed until a sudden fracture occurs (for example, breaking a hip or wrist from a minor fall).¹ In short, osteoporosis means “porous bone”, bones lose strength and can break much more easily than normal.

How does osteoporosis develop in the bones?

The inside of bone is like a honeycomb. In healthy bone, the “walls” of this honeycomb are thick and the spaces are small. In osteoporosis, the walls become thin, the spaces get larger, and the outer shell of the bone thins out, all of which weakens the bone’s structure.¹

Bones might seem hard and unchanging, but they are living tissues that constantly rebuild themselves. In youth, our bodies make new bone faster than they break down old bone, so bones stay dense. Osteoporosis develops when more bone is broken down than is rebuilt.¹ In other words, the body loses bone mass faster than it can replace it. Over time, this imbalance leaves the internal structure of the bone with bigger holes (like a weakening honeycomb), causing bones to become less solid and more fragile.² Aging is a primary reason for this shift – as we get older, bone-building slows down while bone loss speeds up.^1,2 The result is gradually weaker bones that can lead to osteoporosis.

Why does the risk of osteoporosis increase with age?

Age is one of the strongest risk factors for osteoporosis. As part of normal aging, bone density naturally decreases. People reach their peak bone mass (the strongest bones can be) in early adulthood, around their late 20s. After about age 30, the body’s formation of new bone slows down, and bone loss gradually outpaces bone gain.³ The older you get, the faster bone is lost and the weaker your bones become.⁴ This is why osteoporosis is most common in adults over 50.¹ In older age, bones that were once healthy may thin out enough to meet the definition of osteoporosis.¹ In summary, aging causes an imbalance in bone turnover (more loss than build-up), leading to weaker bones and a higher risk of osteoporosis as the years go on.⁴

Why are women more likely to develop osteoporosis than men?

Women are especially prone to osteoporosis. During 2017-2018, around 10 million Americans had osteoporosis, with the condition being more common in females than males aged 50 years or over (13.1% vs. 3.3%).^6,7 There are a few reasons why osteoporosis affects women more:

• Menopause and estrogen loss: Estrogen, a hormone in women, helps protect bone strength. After menopause (when menstrual periods stop, usually around age 45-55), estrogen levels drop sharply, and women can lose bone mass rapidly as a result.⁵ In the first 5-10 years after menopause, women may lose a significant percentage of their bone density because of low estrogen.⁵ Low estrogen is one of the most common causes of bone loss leading to osteoporosis in women⁵. For example, early menopause or removal of the ovaries can cause earlier bone loss due to the sudden decrease in estrogen.⁷

• Lower initial bone mass: Women generally have smaller, thinner bones than men on average.⁵ This means women have less bone “in the bank” to begin with. Men tend to build up a higher peak bone mass during youth due to larger bone size.⁴ If a woman and a man both lose the same percentage of bone with age, the woman’s bones (being smaller) will reach the fragile threshold sooner.⁵

• Longer life span: Women often live longer than men on average.⁵ Bone loss is a slow process, so living more years gives more time for osteoporosis to develop. This partly explains why very elderly women have high rates of fractures.

It’s important to note that men can develop osteoporosis too, especially by older age. Men’s risk increases after about age 70.⁴ Men naturally have more bone mass and no equivalent of menopause, but they do experience a gradual drop in testosterone (which affects bone) as they age. Certain conditions (like low testosterone levels due to medical problems) or long-term use of steroid medications can also put men at risk.⁴ In summary, both sexes can get osteoporosis, but women’s post-menopausal hormone changes and lower initial bone density make it much more common in women.⁴

Can a lack of calcium or vitamin D cause osteoporosis?

Yes. Poor nutrition, especially low calcium and vitamin D intake, is a major cause of weak bones over time.⁴ Calcium and vitamin D are vital for bone health. Calcium is a key mineral that makes bones hard and dense, and vitamin D is needed to help your body absorb calcium properly. If you don’t get enough calcium from your diet (or supplements), your body will take the calcium it needs from your bones, causing your bones to lose mineral content.⁵ Over years, a calcium-deficient diet can significantly lower your bone density.⁴ Vitamin D deficiency also contributes to osteoporosis because without vitamin D, even calcium-rich foods won’t be fully utilized by the body to build bone.⁵

Starting from childhood and through adulthood, a diet consistently low in calcium and vitamin D increases the risk of developing osteoporosis.⁴ People who are undernourished, have eating disorders like anorexia, or follow extreme diets may have weak bones due to lack of calcium, vitamin D, and protein.^4,5 In short, if your body doesn’t get the nutrients it needs for bone maintenance, it will lead to bone loss. This is why doctors recommend getting adequate calcium (through dairy products or other calcium-rich foods) and safe sun exposure or supplements for vitamin D as part of osteoporosis prevention.⁵

(Note: Calcium and vitamin D alone aren’t the only factors, but they are among the most important nutritional factors for bone strength. Lack of these nutrients “plays a role in the development of osteoporosis” by causing lower bone density and faster bone loss.)

Can a sedentary lifestyle (lack of exercise) lead to osteoporosis?

Absolutely. Bones become stronger when you regularly exercise, especially with weight-bearing activities (like walking, jogging, dancing, or lifting weights).^4,5 Conversely, if you are very inactive, your bones can get weaker. Just like muscles, bones will weaken if they aren’t used. People who lead a sedentary lifestyle (sitting or bedbound for long periods) have a higher risk of osteoporosis.³ When you do weight-bearing exercise, you put stress on the bones in a healthy way, which signals your body to build up or maintain bone mass. Without that stress (for example, someone on prolonged bed rest or who is very inactive), the body gets the message that the bones aren’t needed to be as strong, and it may start to reabsorb bone tissue.⁸

Lack of physical activity contributes to an increased rate of bone loss.⁴ For instance, astronauts in zero gravity (no weight-bearing) lose bone quickly, and similarly, a person who is completely inactive will lose bone faster than an active person. Weight-bearing exercises, such as walking, running, dancing, climbing stairs, or resistance training, are especially beneficial for maintaining bone density.^3,5 On the other hand, spending most of your time sitting with no exercise leaves you with weaker bones and muscles, which also raises the risk of falls and fractures.⁴ The message is: use your bones or lose them. Regular physical activity is important to keep bones strong, and a sedentary lifestyle can indeed lead to more rapid bone thinning.

Do smoking and alcohol use cause osteoporosis?

Smoking and heavy alcohol use are both linked to osteoporosis. They are considered lifestyle risk factors that can weaken bones:

• Smoking: Cigarette smoking has a direct harmful effect on bone cells and reduces blood supply to the bones. Smoking is associated with lower bone density and a higher risk of fractures.⁵ In women, smoking can trigger earlier menopause, which means earlier estrogen loss and more years of bone thinning.⁵ Research indicates that smokers have weaker bones, and the damage accumulates with more years of smoking⁵. While the exact mechanism is complex, smoking is clearly identified as a risk factor for osteoporosis and fractures⁴. Quitting smoking is strongly recommended to protect bone health.⁴

• Alcohol: Heavy alcohol consumption is detrimental to bone health. Chronic heavy drinking (more than about 2 drinks a day) can lead to increased bone loss and increases risk factor for osteoporosis.^3,5 People who drink excessively tend to have poorer nutrition (often lacking calcium/vitamin D) and may have more falls. For women, more than one drink per day, and for men more than two, is considered excessive for bone health.³ Studies show that heavy alcohol use reduces bone formation and speeds up bone breakdown, making osteoporosis more likely.^4,5

Bottom line: Both smoking and excessive alcohol can cause bone loss over time. If you smoke, quitting smoking can help reduce further damage to your bones.⁴ If you drink alcohol, moderation is key. Limiting alcohol to no more than one drink a day for women or two for men can help lower the risk of osteoporosis.⁵ Avoiding these habits, along with good nutrition and exercise, gives your bones a better chance to stay strong.

Can certain medical conditions or medications cause osteoporosis?

Yes. Osteoporosis can be secondary to other medical conditions or long-term use of certain medications. In other words, sometimes an illness or a treatment for an illness can lead to bone loss. Here are some examples:

• Corticosteroid medications: Long-term use of glucocorticoid steroids, often prescribed for conditions like asthma, arthritis, or autoimmune diseases, is a well-known cause of medication-related osteoporosis.^4,5 Steroids interfere with the bone rebuilding process and cause bone to break down faster, so extended use can significantly weaken bones.³ People on chronic steroids are often advised to take measures to protect their bones.

• Other medications: Certain anti-seizure medications, breast and prostate cancer treatments that suppress hormones, some proton pump inhibitors (for acid reflux), SSRIs (for depression), and drugs for thyroid disease or diabetes (e.g. thiazolidinediones) have been linked to bone loss with long-term use.⁴ Not every person on these will get osteoporosis, but these meds may contribute to bone thinning over time.

• Hormonal disorders: Thyroid or parathyroid gland overactivity can cause bone loss. Too much thyroid hormone (from an overactive thyroid or taking high thyroid medication doses) makes bones break down faster.³ Overactive parathyroid glands (hyperparathyroidism) also pull calcium out of bones. Diabetes and elevated cortisol levels (such as in Cushing’s syndrome) are other examples of hormonal issues that can weaken bones.³

• Chronic diseases: Rheumatoid arthritis, chronic liver or kidney disease, and malabsorption disorders (like celiac disease or inflammatory bowel disease) can increase osteoporosis risk.³ These conditions either cause chronic inflammation, affect nutrient absorption, or require medication (like steroids) that harm bones. Certain types of cancer (such as multiple myeloma or treatments for cancer) can also directly or indirectly cause bone loss.³

• Eating disorders or nutritional diseases: Severe anorexia nervosa (an eating disorder causing low body weight and malnutrition) leads to low estrogen and nutrient deficiencies, resulting in significant bone loss.^1,5 Similarly, conditions that cause long periods of immobilization or bed rest can lead to osteoporosis.¹

In all these cases, the osteoporosis is a result of another primary cause, be it a drug’s side effect or a disease process.⁴ Doctors call this secondary osteoporosis. If you have a condition or take a medication known to affect bone health, your healthcare provider may monitor your bone density or recommend preventive measures (like calcium/Vitamin D supplements or osteoporosis medications). Managing the underlying condition and mitigating risk factors (for example, using the lowest effective steroid dose for the shortest time necessary) can help reduce bone loss.⁵

Is osteoporosis hereditary?

Family history does play a role in osteoporosis. If your parents or siblings have osteoporosis, especially if a parent had a history of fractures (like a broken hip), your own risk of developing osteoporosis is higher.³ Genetics strongly influence how much bone mass you accumulate in your youth (peak bone mass) and how rapidly you lose bone as you age.^4,9 For example, having a mother with osteoporosis could mean you inherited a tendency for lower bone density.⁴ Research suggests that your genes account for a significant portion of your bone strength, for instance, studies of families and twins show that bone mineral density is partly inherited.⁹

However, genetics is not the only cause. You can think of it this way: genetics loads the gun, but lifestyle pulls the trigger. If you know osteoporosis “runs in the family,” it’s even more important to pay attention to lifestyle factors (diet, exercise, etc.) to counteract that risk.¹ Also, certain inherited conditions (like osteogenesis imperfecta, a rare brittle bone disease) cause severe bone fragility, but in general, common osteoporosis is polygenic (influenced by many genes each having a small effect).^10,11

In summary, osteoporosis can run in families, and a family history is considered a notable risk factor.⁴ If one of your parents had osteoporosis or a fracture related to bone thinning, be proactive about bone health. This includes getting sufficient calcium/vitamin D, doing weight-bearing exercise, and discussing bone density screening with your doctor as you get older.⁵

What can I do to help prevent osteoporosis?

While you can’t change factors like age or genetics, there are several steps you can take to prevent or slow osteoporosis. Building strong bones early in life and maintaining them through adulthood is the best defense. Here are some key prevention tips:

• Get enough calcium and vitamin D: Ensure you have a calcium-rich diet (dairy products, leafy greens, fortified foods) and adequate vitamin D (through sensible sun exposure or supplements) to support bone formation.⁵ A lifelong sufficient intake of calcium and vitamin D helps maximize bone density and slow bone loss.^4,5 If you don’t get enough from food, talk to a doctor about supplements.

• Engage in regular exercise: Weight-bearing and muscle-strengthening exercises are great for bones.³ Activities like walking, jogging, dancing, climbing stairs, or lifting weights help stimulate bone cells to grow stronger.⁵ Aim for at least moderate exercise most days, with a focus on activities that put gentle stress on bones.² Exercise not only builds bone mass when you’re younger, but also helps maintain balance and strength in older age to prevent falls.⁵

•Avoid smoking and limit alcohol: As discussed, smoking weakens bones, and heavy alcohol accelerates bone loss. Not smoking (or quitting if you do) and keeping alcohol to a minimum (no more than 1-2 drinks per day) will help preserve your bone strength.^4,5 These lifestyle changes have numerous other health benefits as well.

• Maintain a healthy body weight: Being too thin or underweight can increase osteoporosis risk (often due to poor nutrition and lower estrogen levels).^4,5 On the other hand, obesity isn’t protective for bone and comes with other risks. Aim for a balanced diet with sufficient calories and protein to support bone tissue.

• Prevent falls and injuries: Especially for older adults, preventing fractures is crucial. Keep your home safe (remove loose rugs, ensure good lighting), work on balance exercises, and have your vision checked. All to reduce the chance of falls.¹⁵ Strong bones help, but preventing the trauma that could break a bone is equally important.

• Medical check-ups and bone density tests: If you have risk factors or are a woman over 65 (or a man over 70), ask your doctor about a bone mineral density test.⁵ This X-ray test i.e. dual-energy X-ray absorptiometry (DEXA) scan can detect osteoporosis early, before fractures happen. If you’re at high risk, your doctor might recommend medications that help prevent bone loss or even strengthen bones.⁵ There are effective prescription treatments (like bisphosphonates, or other newer drugs) that can slow bone loss or help build bone mass.⁵

By addressing modifiable risk factors – nutrition, exercise, and lifestyle – you can reduce your chances of developing osteoporosis.⁵ Even if you already have some bone loss, these steps can slow it down. It’s never too early or too late to invest in healthier bones. Building bone density when you are young and slowing bone loss as you age is the formula for preventing osteoporosis and the broken bones it can cause.

Q: Can men get osteoporosis?

A: Yes. Although osteoporosis is often seen as a women’s disease, men can absolutely develop osteoporosis. Men tend to start losing bone later in life than women, but by age 70 men’s risk of osteoporosis increases significantly.⁴ Men with certain risk factors (such as long-term steroid use, low testosterone, smoking, or excessive alcohol use) can get osteoporosis even earlier.^3,4,5 In fact, about 20% of osteoporosis cases occur in men⁵. So, men (especially older men) should also be mindful of bone health.

Q: At what age does osteoporosis usually occur?

A: Osteoporosis becomes more common as people get older, typically after age 50.¹ Women often experience accelerated bone loss around menopause (late 40s to 50s), so they may develop osteoporosis in their 50s or 60s. Men generally develop osteoporosis a bit later, often in their 70s, because they don’t have the same sudden hormone changes. That said, osteoporosis can occur in younger adults in certain cases (for example, due to medical conditions or extreme dieting), but the vast majority of osteoporosis cases are in seniors. By age 65–70, both women and men should be evaluated for osteoporosis risk.⁵

Q: What are the early signs of osteoporosis?

A: Osteoporosis is usually “silent” with no early signs or symptoms. You typically won’t feel your bones getting weaker. Most people find out they have osteoporosis after a fracture – for example, breaking a bone from a minor fall that would not have harmed a healthy bone.¹ Some indirect clues of osteoporosis (after it’s advanced) include loss of height or a stooped posture in older adults, which happen due to small fractures in the spine.^2,3 But there is generally no pain or obvious symptom as bones lose density. This is why osteoporosis is often called the “silent disease”.¹ Regular bone density screenings are important for at-risk individuals to detect osteoporosis before fractures occur.⁵

Q: How is osteoporosis diagnosed?

A: Doctors diagnose osteoporosis with a bone density test, usually a DEXA scan. This scan is a quick, low-dose X-ray that measures the density of your bones (often at the hip and spine) to see if you have osteoporosis or are at risk.² The result is given as a T-score; a score of –2.5 or lower indicates osteoporosis.¹³ Your healthcare provider might order this test if you’re a woman over 65, a man over 70, or younger with risk factors.⁵ The test is painless and is the best way to detect osteoporosis early. In addition to the DEXA scan, your doctor will consider your medical history, any history of fractures, and possibly do blood tests to rule out secondary causes.

Q: Can osteoporosis be cured or reversed?

A: There is currently no complete “cure” to fully reverse osteoporosis, but it can be managed, and its progression can be slowed (and sometimes partially improved). Treatments like bisphosphonate medications, hormone-related therapy, or newer bone-building drugs can halt further bone loss and even increase bone density modestly.⁵ Lifestyle changes, such as improving diet, taking calcium and vitamin D, exercising, and quitting smoking, are also crucial in strengthening your bones and preventing fractures.⁵ While lost bone isn’t totally restored to youthful levels, people with osteoporosis can significantly improve their bone strength and reduce fracture risk with proper treatment and healthy habits.¹⁴ The goal is to stabilize bone density and prevent fractures. Always consult your doctor for the best plan; early intervention yields the best results.

This article was written with the assistance of generative AI technology and reviewed for accuracy.

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