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.
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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 when bone density has decreased. 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 (fractures). 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 treatment to lower your risk of osteoporosis and fractures.

Osteoporosis

 

This illustration shows a normal bone with a lot of small holes in the spongy bone area, and a bone with osteoporosis that has much larger holes.
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.

 

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. 

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

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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

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