What causes bone loss?


Osteoporosis, or weak bones, is a disease that causes bones to become brittle and more likely to fracture (break). With osteoporosis, the bones lose density. Bone density is the amount of calcified bone tissue that is in your bones.

A diagnosis of osteoporosis means you are at risk for bone fractures even with everyday activities or minor accidents or falls.

Video: Osteoporosis

Alternative Names

Osteoporosis - causes; Low bone density - causes

Your Changing Bones

Your body needs the minerals calcium and phosphate to make and keep healthy bones.

  • During your life, your body continues to both reabsorb old bone and create new bone. Your entire skeleton is replaced about every 10 years, though this process slows as you get older.
  • As long as your body has a good balance of new and old bone, your bones stay healthy and strong.
  • Bone loss occurs when more old bone is reabsorbed than new bone is created.

Sometimes bone loss occurs without any known cause. Some bone loss with aging is normal for everyone. Other times, bone loss and thin bones run in families and the disease is inherited. In general, white, older women are the most likely to have bone loss. This increases their risk of breaking a bone.

Brittle, fragile bones can be caused by anything that makes your body destroy too much bone, or keeps your body from making enough bone.

Weak bones can break easily, even without an obvious injury.

Bone mineral density is not the only predictor of how fragile your bones are. There are other unknown factors related to bone quality that are as important as bone quantity. Most bone density tests only measure the bone quantity.

Aging and Bone Loss

As you age, your body may reabsorb calcium and phosphate from your bones instead of keeping these minerals in your bones. This makes your bones weaker. When this process reaches a certain stage, it is called osteoporosis.

Many times, a person will fracture a bone before they even know they have bone loss. By the time a fracture occurs, the bone loss is serious.

Women over age 50 years and men over age 70 years have a higher risk for osteoporosis than younger women and men.

  • For women, a drop in estrogen at the time of menopause is a major cause of bone loss.
  • For men, a drop in testosterone as they age can cause bone loss.

What's Your Osteoporosis Risk?

If you have good posture, you don't need to worry about osteoporosis.

The correct answer is myth. People with osteoporosis have weak bones that are more likely to break. Bone loss from osteoporosis can lead to a stooped posture. Bad posture can cause stooping, but it doesn't cause bone loss or osteoporosis. Discuss your risk factors for osteoporosis with your doctor even if your posture is perfect!

Half of women over age 50 will fracture a hip, wrist or vertebra.

The correct answer is true. Half of women over age 50 will fracture a hip, wrist, or vertebra during their lifetime. This is because many women lose a lot of bone as they get older. Finding osteoporosis early can help prevent bone breaks.

Going through menopause:

The correct answer is raises your risk of osteoporosis. During menopause, estrogen levels fall, and the body may not be able to create new bone fast enough to replace the old bone used by the body. If you have gone through menopause, ask your doctor about being tested for osteoporosis.

Men don't get osteoporosis.

The correct answer is myth. As men age, testosterone levels tend to fall. This can lead to bone loss starting at about age 70. Older men should talk with their doctor about being tested for osteoporosis.

Which group is most at risk for osteoporosis?

The correct answer is Caucasians. White women are more likely to develop brittle bones than any other group. The risk is highest in women with a family history of osteoporosis. If the disease runs in your family, talk to your doctor about osteoporosis prevention and bone density testing.

Eating foods high in calcium can lower your osteoporosis risk.

The correct answer is fact. Your body needs calcium to build strong bones. Women ages 51 to 70 should have 1,200 mg of calcium a day. Men ages 51 to 70 and adults age 50 or younger should have 1,000 mg of calcium a day. In addition, everyone needs 400 to 800 IU of vitamin D daily to help the body absorb calcium.

Which exercise can lower your osteoporosis risk?

The correct answer is B and D. Weight-bearing exercises make your muscles pull on your bones. This makes bones stronger. Examples include tennis, walking, dancing, and weight-lifting. Protect your bones by doing weight-bearing exercises 3 or more days a week. Check with your doctor first if you haven't been active for awhile.

Drinking and smoking can increase your osteoporosis risk.

The correct answer is fact. Men and women who smoke have weaker bones. Women who smoke after menopause have an even higher chance of bone breaks. Having three or more alcoholic drinks a day on most days can also damage the bones. Your doctor can help if you decide to quit smoking or cut back on alcohol.

Which health problem raises the risk of osteoporosis?

The correct answer is all of the above. Any health problem that makes it hard to exercise or keeps the body from absorbing calcium or vitamin D can lead to weak bones. Some medicines, including steroids and anti-seizure drugs, can also cause osteoporosis.

You're more likely to get osteoporosis if you're overweight.

The correct answer is myth. In fact, people who are underweight are more likely to get osteoporosis. Younger woman who do not have menstrual periods for a long time also have a higher risk of bone loss.

Bone density testing can spot osteoporosis before it causes symptoms.

The correct answer is fact. Bone density testing is a painless scan that measures how much calcium and other minerals are in a section of bone. Women over 65 and men over 70 should consider having this test. Ask your doctor about starting earlier if you have any of the risk factors discussed in this quiz.

Your Lifestyle and Bone Loss

Your body needs calcium and vitamin D and enough exercise to build and keep strong bones.

Calcium source

Calcium source

Vitamin D benefit

Vitamin D benefit

Your body may not make enough new bone if:

  • You do not eat enough high-calcium foods
  • Your body does not absorb enough calcium from the foods you eat
  • Your body removes more calcium than normal in the urine

Certain habits can affect your bones.

  • Drinking alcohol. Too much alcohol can damage your bones. It can also put you at risk of falling and breaking a bone.
  • Smoking. Men and women who smoke have weaker bones. Women who smoke after menopause have an even higher chance of fractures.

Younger women who do not have menstrual periods for a long time also have a higher risk of bone loss and osteoporosis.

Low body weight is linked to less bone mass and weaker bones.

Exercise is linked to higher bone mass and stronger bones.

Medical Disorders and Bone Loss

Many long-term (chronic) medical conditions can keep people confined to a bed or chair.

  • This keeps the muscles and bones in their hips and spines from being used or bearing any weight.
  • Not being able to walk or exercise may lead to bone loss and fractures.

Other medical conditions that may also lead to bone loss are:

Sometimes, medicines that treat certain medical conditions can cause osteoporosis. Some of these are:

  • Hormone-blocking treatments for prostate cancer or breast cancer
  • Some medicines that are used to treat seizures or epilepsy
  • Glucocorticoid (steroid) medicines, if they are taken by mouth every day for more than 3 months, or are taken several times a year

Any treatment or condition that causes calcium or vitamin D to be poorly absorbed can also lead to weak bones. Some of these are:

  • Gastric bypass (weight-loss surgery)
  • Cystic fibrosis
  • Other conditions that prevent the small intestine from absorbing nutrients well

People with eating disorders, such as anorexia or bulimia, are also at higher risk for osteoporosis.

What's Next?

Talk to your health care provider about your risk for bone loss and osteoporosis. Find out how to get the right amount of calcium and vitamin D, what exercise or lifestyle changes are right for you, and what medicines you may need to take.


Vitamin D benefit
Calcium source


De Paula FJA, Black DM, Rosen CJ. Osteoporosis: basic and clinical aspects. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ , eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 30.

Eastell R, Rosen CJ, Black DM, Cheung AM, Murad MH, Shoback D. Pharmacological management of osteoporosis in postmenopausal women: an Endocrine Society* Clinical Practice Guideline. J Clin Endocrinol Metab. 2019;104(5):1595-1622. PMID: 30907953 pubmed.ncbi.nlm.nih.gov/30907953/.

Weber TJ. Osteoporosis. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 230.

Review Date: 
Reviewed By: 
Brent Wisse, MD, board certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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