Osteoporosis and bone health: what it is and why fractures matter

A diagnosis of osteoporosis, or a letter saying your bone density is "low," can feel abrupt, especially when nothing hurts. This guide explains what the condition is, how bone changes across a lifetime, which factors raise risk, who is usually offered screening, and where the hormone system fits in. It also covers the honest limits of what a scan can predict. Individual care varies, and your own doctor or specialist has the final word on anything that applies to you.

What osteoporosis is

Osteoporosis is a bone disease in which bone mass and bone strength fall far enough that bones break more easily. The Bone Health and Osteoporosis Foundation (BHOF) describes it as a condition that occurs when the body loses too much bone, makes too little bone, or both. The word itself means "porous bone."

It is often called a silent disease. The U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) notes that symptoms usually do not appear until a bone breaks, and that the hip, the vertebrae of the spine and the wrist are the sites that break most often. That silence is why screening exists, and also why a diagnosis can come as a surprise.

How bone renews itself

Bone is living tissue. It is constantly being taken apart and rebuilt in a cycle called remodeling. According to the BHOF, the cycle has two distinct stages: cells called osteoclasts break down old bone (resorption), and cells called osteoblasts then fill the cavities with new bone (formation). In healthy bone the two stages stay balanced. With aging, more old bone is removed than new bone is created.

The balance shifts over a lifetime. The American Academy of Orthopaedic Surgeons' patient site, OrthoInfo, says most people reach their peak bone mass between the ages of 25 and 30, and that about 95% of a young woman's peak bone mass is already present by age 20. Up to about age 40, the bone that is removed is replaced. After that, less is replaced, and bone mass slowly declines.

Peak bone mass matters because it is the starting balance. People who built more bone when young have more to draw on later. The BHOF puts it simply: the greater your bone density is to begin with, the lower your chance of developing osteoporosis. Genetics play a large part in that starting point, so it is not something anyone fully controls.

Age-related bone loss and the menopause years

Bone loss is gradual for most adults, but it is not steady for everyone. For women, the years around menopause are the fastest stretch. Estrogen helps restrain bone breakdown, and when it drops, resorption outpaces formation. The BHOF states that a woman can lose up to 20% of her bone density during the five to seven years following menopause. Our guide to menopause and bone health covers that period in more detail.

Men are not exempt. They tend to have a higher peak bone mass and lose bone later, but OrthoInfo notes that men face rising risk of low bone mass and fractures after about age 70. Neither sex is simply "safe."

Risk factors as the major sources list them

Risk factors fall into two groups: those you cannot change, and those you can influence. NIAMS lists, among the first group, being female, older age, a slender or thin-boned frame, family history (a parent with osteoporosis or a hip fracture) and ancestry, with non-Hispanic white and Asian women at highest risk in U.S. data. In the second group it lists low calcium and vitamin D intake, very restrictive dieting, inactivity, smoking and heavy long-term alcohol use.

The BHOF adds a list of medical conditions that can lower bone density: autoimmune disorders such as rheumatoid arthritis, digestive disorders such as celiac disease, certain cancers, chronic kidney or liver disease, COPD, poor nutrition, and endocrine conditions such as diabetes and hyperthyroidism. Both organizations caution that their lists may be incomplete, so a doctor is the right person to weigh your own picture.

Hormone-related and medicine-related causes

When osteoporosis has an identifiable cause besides aging, clinicians call it secondary. Many of the common causes involve the endocrine system, which is why this site covers bone and hormones together. At a general level, these are the ones that appear most often in public guidance.

• Low sex hormones. NIAMS names low estrogen after menopause, long absences of menstrual periods before menopause, and low testosterone in men from conditions that cause it. It adds that the gradual testosterone decline of normal aging is probably not a major cause.
• Overactive thyroid. The BHOF lists hyperthyroidism among the conditions that can affect bone. Our thyroid health basics page explains the gland itself.
• Overactive parathyroid glands. The U.S. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains that in primary hyperparathyroidism, high parathyroid hormone levels trigger the bones to release more calcium than normal into the blood, and the loss of calcium from bone may weaken it. See the parathyroid glands and calcium for the wider picture.
• Glucocorticoids. Long-term steroid tablets are one of the best-known medicine-related causes. The BHOF cites pills at 5 mg or more for three months or longer as a point of concern. NIAMS also lists several other long-term medicines, including some seizure medicines and hormone-based breast and prostate cancer drugs.
• Diabetes. The BHOF includes diabetes among the endocrine conditions linked to bone problems. Our diabetes and metabolic health guide covers the condition itself.

None of this means that having one of these conditions guarantees bone loss. It means bone health is worth raising with the clinician who manages that condition, because the answer depends on the person.

Fractures are the outcome that matters

A low bone density number is a risk marker. The thing people actually want to avoid is a fracture. The BHOF states that one in two women and up to one in four men age 50 and older will break a bone due to osteoporosis. It also reports that twenty percent of seniors who break a hip die within one year from related complications or surgery. These are U.S.-focused figures from one organization, and rates differ between countries and populations, but they show why prevention is taken seriously.

Spine fractures can be quieter. Some cause sudden back pain, while others go unnoticed and show up later as lost height or a stooped posture. Recovery after any fracture is its own topic, covered in fracture recovery and rehabilitation.

Who is usually screened, and why guidance differs

Screening means testing people who have no known osteoporosis in order to find it early. The standard tool is a DXA scan of the hip and spine, explained step by step in the bone density test (DXA) explained. Who should be offered one depends on which group you ask, and recommendations differ by country.

The U.S. Preventive Services Task Force (USPSTF), in its January 2025 statement, recommends screening in women 65 years or older, and in postmenopausal women younger than 65 who are at increased risk based on a clinical risk assessment. For men, it concludes the evidence is insufficient to weigh the benefits and harms, and leaves the decision to clinical judgment. That statement applies to adults 40 or older without known osteoporosis, and it does not cover people whose bone loss comes from a condition or a medicine such as glucocorticoids.

The BHOF is broader. It says women 65 and older, men 70 and older, anyone who has broken a bone after age 50, women 50 to 64 and men 50 to 69 with risk factors should have a bone density test. Other countries and societies draw the lines in other places again. If you live outside the United States, your national guideline may recommend something different, and your doctor will know which one applies where you are.

The honest limits of screening

A scan is useful, but it is not a crystal ball. Two people with the same score can have very different outcomes, because falls, past fractures, age and other factors all matter. Fracture risk calculators such as FRAX try to combine these factors, and the USPSTF notes that FRAX has no defined screening threshold. In plain terms, nobody has drawn a bright line.

The USPSTF also points out that repeating bone density testing at an interval of 4 to 8 years did not improve accuracy in predicting fractures, and its statement gives no recommended interval. Screening can find people who may benefit from treatment. It cannot promise that treatment will prevent a particular person's fracture, and it cannot predict one with certainty.

Prevention basics

Prevention is mostly ordinary habits, and no single one does the job alone. NIAMS lists weight-bearing exercise such as walking, moderate alcohol intake, not smoking, and a diet that supplies calcium and vitamin D. The calcium and vitamin D details are in calcium and vitamin D basics, and how to move for bone strength is in exercise and bone loading.

Fall prevention belongs on the list too, since falls are a common way for fractures to happen. Practical steps for the home are in fall prevention at home. For people who already have osteoporosis or a high fracture risk, medicines are an additional option that clinicians decide on case by case, and an overview of how osteoporosis medicines work explains the main classes without recommending any. A list of useful questions for an appointment is in questions to ask an endocrinologist.

The short version

Osteoporosis is a quiet loss of bone strength that matters because of the fractures it can lead to. Bone is built early, lost gradually, and lost faster for some people when hormones, medicines or other conditions are involved. Screening guidance varies by country and has real limits, so the numbers are best read with a clinician who knows your history.