Osteoporosis causes bones to become weaker and more fragile. Some people are more at risk than others.
Bones are thickest and strongest in your early adult life until your late 20s. You gradually start losing bone from around the age of 35.
This happens to everyone, but some people develop osteoporosis and lose bone much faster than normal. This means they're at greater risk of a fracture.
Osteoporosis can affect men and women. It's more common in older people, but it can also affect younger people.
Women are more at risk of developing osteoporosis than men because the hormone changes that happen at the menopause directly affect bone density.
The female hormone oestrogen is essential for healthy bones. After the menopause, oestrogen levels fall. This can lead to a rapid decrease in bone density.
Women are at even greater risk of developing osteoporosis if they have:
In most cases, the cause of osteoporosis in men is unknown. However, there's a link to the male hormone testosterone, which helps keep the bones healthy.
Men continue producing testosterone 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 low testosterone levels is unknown, but known causes include:
Many hormones in the body affect bone turnover. If you have a disorder of the hormone-producing glands, you may have a higher risk of developing osteoporosis.
Hormone-related disorders that can trigger osteoporosis include:
Other factors thought to increase the risk of osteoporosis and broken bones include:
You can find out if you're at risk by doing the Royal Osteoporosis Society's online test.