Bone thinning and osteoporosis

Getting older and some cancer treatments can reduce bone density. This is called bone thinning. It can lead to a condition called osteoporosis.
On this page

What causes bone thinning?

Bones are living tissue. They have a blood and nerve supply to keep them healthy. Bones are constantly being renewed. This helps maintain their strength and shape.

Inside the bones, there are 2 types of bone cell:

  • Osteoclasts which break down and remove old bone.
  • Osteoblasts which build new bone.

Our bones stop growing in length by the time we are about 18 years old, but they may continue to grow into our early to mid 20s. Bones continue to increase in thickness (density) until our late 20s and stay about the same until our mid-30s.

Bone density means how strong your bones are. It is the amount of calcium and minerals in your bone. Denser bones are stronger, and this means they are less likely to break. After our mid-30s, bone density slowly decreases. This is because osteoclasts remove more bone tissue than osteoblasts make. This means the amount of bone tissue starts to decrease.

As we get older, our bone density slowly decreases. This is called bone loss or bone thinning.

The hard, outer layer of the bones (compact bone) gets thinner and the holes in cancellous (spongy) bone get larger. In time, bones become more fragile. This is why bone fractures are more common after the age of 65.

Can cancer cause bone thinning?

Some cancer treatments can affect your bone health, and cause more bone loss than usually happens with age. For example, some drugs such as hormonal therapy or targeted therapy drugs can cause bone loss. Radiotherapy can also cause changes to the bone.

MACIG043 Bone mass chart
Image: This infographic shows a graph of bone mass at different ages. The upright axis on the left side is labelled bone mass. The level axis across the bottom is labelled age in years. It is marked from 0 years to 80 years in regular 10-year intervals going from left to right. There are two lines on the graph. One line shows bone mass changes over time in women, and the other shows bone mass changes over time in men. The picture shows that bone mass is greater in males than in females at all ages. This difference is slight in boys and girls but the gap between the lines increases in the teens as the line for men slopes upwards more steeply. By the age of 20, the line for men is clearly higher than for women and remains this way for the rest of the graph. Both lines show bone mass increasing from birth until the late 20s. There is a label attached to both lines at this highest point, which says peak bone mass. The lines then begin to slope down gently, showing a gradual decrease in bone mass. This gradual decline continues for men until the 80-year mark. But at the 50-year mark for women, the line begins to slope down much more steeply. This point on the women’s line is labelled menopause. The line for women then continues to slope down less steeply from the age of 60 onwards.

What is osteoporosis?

Osteoporosis is a condition when bone density is much lower than the average adult. This means the bones are weaker and more likely to break (fracture). Some people develop osteoporosis as they get older. Fractures are most common in the wrists, hips and spine.

Osteoporosis does not cause symptoms until a weakened bone breaks. But your doctor can do tests to assess your risk of osteoporosis and check the strength of your bones. The results of these tests help doctors decide if you need drug treatment to lower your risk of osteoporosis and fractures.

Osteopenia

You may be told you have osteopenia. This means your bone density is lower than the average adult, but not low enough to be osteoporosis.

We have more information about tests to check for bone health.

Your doctor can give you advice on things you can do to help lower your risk of osteoporosis.

We also have more information about bone health and looking after your bones.

Osteoporosis

MACD175 Osteoporosis
Image: The illustration shows the structure of a normal bone and the structure of a bone with osteoporosis. In the normal bone, the spongy bone area has a lot of small holes. In the bone with osteoporosis, the spongy bone area has much larger holes.

Related pages

About our information

This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer.

Cancer Information Development team

Author

Macmillan Centre of Clinical Expertise

Reviewer

Date reviewed

Reviewed: 01 August 2024
|
Next review: 01 August 2027
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.

The language we use


We want everyone affected by cancer to feel our information is written for them.


We want our information to be as clear as possible. To do this, we try to:

  • use plain English
  • explain medical words
  • use short sentences
  • use illustrations to explain text
  • structure the information clearly
  • make sure important points are clear.

We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.


You can read more about how we produce our information here.

Print page

How we can help

Macmillan Support Line
The Macmillan Support Line is a free and confidential phone service for people living and affected by cancer. If you need to talk, we'll listen. 

 

Call us on 0808 808 00 00
8am to 8pm. It's free to call from landlines and mobiles within the UK.
Email us
Get in touch via this form
Chat online
Every day 8am - 8pm.
Online Community

Chat online anonymously to others who understand what you are going through. Our community is available 24/7 and has dedicated forums where you can get advice and ask our experts.
Find local cancer support services
What's going on near you? Find out about support groups, where to get information and how to get involved with Macmillan where you live.
Get help