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Hormone therapy treatments can lower the levels of sex hormones in the body. The main female sex hormones are oestrogen and progesterone.
Lower levels of these hormones can increase bone loss.
Bone loss (osteoporosis) and ageing
Our bones start to thin around our late thirties. This is part of the natural ageing process.
The bones go through a stage called osteopenia. This is when they start to become thinner. Osteoporosis is when the bones become more brittle and thinner. Having thinner bones makes them more at risk of breaking (fracture).
After the menopause 
the levels of the sex hormone oestrogen decrease. This increases bone loss.
Bone loss and breast cancer treatment
Some cancers use hormones to grow or develop. Doctors call these hormone dependent or hormone sensitive breast cancers. Hormone therapy works by blocking or lowering the amount of these hormones.
We know from research that people having some types of hormone therapy for breast cancer have increased bone loss compared to other people of the same age. This means they are at higher risk of breaking a bone.
Talk to your specialist about whether you have a risk of bone weakening. There are steps you can take to help keep your bones healthy, such as drug treatment.
Some breast cancer treatments aim to stop your body producing particular sex hormones or block their action.
Tamoxifen
Tamoxifen is a type of hormone therapy used to treat hormones sensitive breast cancers. It blocks the effects of oestrogen on breast cancer cells.
In pre menopausal women it can cause some bone loss if you have tamoxifen on its own. But if you take tamoxifen with treatment to stop the ovaries from working (ovarian suppression) there is a bigger risk of bone thinning.
In post menopausal women, tamoxifen can increase bone density. So it can protect the bones.
Aromatase inhibitors (AI)
Aromatase inhibitors are the main hormone treatment used for post menopausal women. They reduce the amount of oestrogen in the body.
Research has shown that all AIs can increase the risk of osteoporosis. There is some evidence that bone strength may recover when treatment has stopped.
They include:
- anastrozole
- exemestane
- letrozole
Stopping the ovaries from working (ovarian suppression)
If you are pre menopausal you might take medicines to switch off your ovaries. Or you might choose to have your ovaries removed.
This causes a sudden menopause in women who have not yet had their menopause. Oestrogen levels suddenly drop and this increases the risk of bone loss.
Hormone replacement therapy (HRT)
You might be able to have hormone replacement therapy (HRT) to help control symptoms caused by low hormone levels. But some treatments for breast cancer aim to either stop the body producing sex hormones or block their action. If you are having these treatments, you can’t unfortunately take HRT.
Doctors don’t routinely recommend that you take HRT if you have had a hormone dependent cancer . Even if you have finished treatment there is concern that HRT may increase the risk of the cancer coming back. Your doctor can explain if HRT is an option for you.
Tests for bone loss
A bone density scan uses low dose x-rays to take measurements to work out the strength of your bones. It is also known as a DEXA or DXA scan.
Your doctor will assess your risk of bone loss and let you know if you need a bone density scan and how often.
Reducing the risk of bone loss
There are different things you can do to reduce your risk of bone loss. These include:
- making sure your diet has enough calcium and vitamin D
- exercising regularly
- taking medicines called bisphosphonates
Calcium
Adults should have about 700 milligrams of calcium every day for good bone health.
Our main dietary source of calcium is dairy products. You’re unlikely to be short of calcium if you eat a normal, balanced diet including dairy foods. But not everyone eats dairy.
Main sources of calcium
You get the most calcium from milk, cheese, and yoghurt. But if you don’t eat dairy foods, there is also calcium in:
- green vegetables, such as cabbage, broccoli and okra
- soya products, including tofu
- tinned fish where you eat the bones (sardines, salmon and pilchards)
- nuts
- dried fruit
- fortified breakfast cereals
Substitute milk, such as rice milk, oat milk and soya milk can also have added calcium. Check the label to find out how much they contain.
Other sources of calcium
There is calcium in tap water, but the amount varies depending on how hard the water is in your area. Some fruit juices and bottled waters have added calcium.
Vitamin D
For your body to use calcium, you also need vitamin D. Your body needs sun to make vitamin D. There is vitamin D added to some fat spreads and breakfast cereals. It’s also found in oily fish and egg yolk.
Public Health England recommends that in winter and autumn, people in the UK should consider taking a daily supplement of vitamin D containing 10 micrograms. This is because it is difficult for people to get enough vitamin D through their diet.
You may want to ask your doctor or specialist nurse for a referral to a dietician at the hospital. A dietician can help you to work out whether you are getting enough calcium and vitamin D in your diet.
Exercise
Exercise is important for bone health. It can also help you lower the risk of a fall that may result in a fracture.
To have an effect on bone thinning, we know this has to be weight bearing exercise. Swimming doesn’t help, because your bones aren’t supporting your weight.
Many of us don’t do enough regular exercise. Bringing exercise into your daily life is the best way to make sure you get enough.
Tips:
- Walking is good.
- Household activities can also help, such as cleaning, gardening, shopping or even going up and down stairs.
- You could join an exercise group or class – it doesn’t have to be very energetic, gentle controlled exercise such as Tai Chi can be good.
- Although swimming doesn’t help, exercise classes that you take at the swimming pool (aqua aerobics) can, because of the resistance of the water.
The most important thing is that you get into the habit of exercise, however you choose to do it.
Don’t jog or take exercise that involves jumping if you’ve already got osteoporosis, or if there is any other reason why you need to take care. It puts too much strain on your bones. Take advice from your doctor before starting any new exercise.
Alcohol and smoking
Drinking alcohol increases the risk of bone loss. National guidelines recommend that you don’t drink more than a total of 14 units of alcohol per week.
Smoking can also increase bone loss. If you smoke the advice is to stop.
Medicines to help bone loss
Bones are naturally breaking down and repairing themselves continually. Hormone therapy can make bones break down faster than they are repairing themselves. This makes them weaker.
Bisphosphonates
Bisphosphonates are a group of drugs that slow down bone loss. They move calcium cells from your blood stream into your bone. This helps to keep the bones strong.
For post menopausal women with breast cancer, bisphosphonate treatment can:
- strengthen the bones
- reduce the risk of breast cancer spreading to the bones
Bisphosphonates include:
- zoledronic acid (Zometa)
- sodium clodronate (Bonefos, Loron)
They can cause side effects, such as an upset stomach and flu-like symptoms. They can also affect the way your kidneys work.
Denosumab
Denosumab works in a different way than bisphosphonates. It stops the activity of bone cells called osteoclasts. Denosumab can increase bone density to help strengthen the bone.
There is also some evidence that it can reduce fractures in post-menopausal women taking aromatase inhibitors.
