Osteoporosis is caused by bones losing their density. Some people are more at risk than others.
How does osteoporosis develop?
Bones are at their thickest and strongest in early adult life and are constantly renewed and repaired through a process called bone turnover. However, as you age, this process is no longer balanced and bone loss increases. This means bone is very slowly broken down over time and your bones become less dense as you get older. This leads to the bone becoming weaker and more likely to fracture.
Who is at risk of osteoporosis?
Osteoporosis can affect men and women. It is more common in older people, but it can affect younger people too.
Women are at greater risk of developing osteoporosis than men. This is because changes in hormone levels can affect bone density. The female hormone oestrogen is essential for healthy bones. After the menopause, the level of oestrogen in the body falls, and this can lead to a rapid decrease in bone density. Women are at an even greater risk of developing osteoporosis when:
- they have an early menopause (before the age of 45)
- they have a hysterectomy before the age of 45, particularly when the ovaries are also removed
- their periods are absent for a long time (more than six months) as a result of over-exercising or over-dieting.
For most men who develop osteoporosis, the cause is unknown. However, there is a link to the male hormone testosterone, which helps to keep the bones healthy. Men continue to produce this hormone into old age, but the risk of osteoporosis is increased in men with low levels of testosterone.
In around half of men the exact cause of this is unknown, but known causes include:
- the use of certain medications such as oral glucocortoids drugs (used for rheumatoid arthritis)
- alcohol misuse
- hypogonadism - a condition that causes abnormally low testosterone levels.
Diseases of the hormone-producing glands
Many hormones in the body can affect the process of bone turnover. If you have a disease of the hormone-producing glands, you may be at higher risk of developing osteoporosis. Osteoporosis can be triggered by hormone-related diseases, including:
- hyperthyroidism (overactive thyroid gland)
- disorders of the adrenal glands, such as Cushing's syndrome
- reduced amounts of sex hormones (oestrogen and testosterone)
- disorders of the pituitary gland
- hyperparathyroidism (overactivity of the parathyroid glands).
Other things thought to increase the risk of osteoporosis and broken bones include:
- a family history of osteoporosis
- a parental history of hip fracture
- a low body mass index (BMI of 19kg per m² or less)
- long-term use of high-dose corticosteroid treatment (widely used for conditions such as arthritis and asthma), which can affect bone strength
- heavy drinking and smoking
- rheumatoid arthritis
- malabsorption problems, as experienced in coeliac disease and Crohn's disease
- some drugs used in breast cancer and prostate cancer treatment which affect hormone levels
- long periods of inactivity, such as long-term bed rest.
Source: NHS Choices, UK (Causes of osteoporosis)
Last reviewed: June 2015