Hormonal treatments lower the levels of sex hormones in the body. These hormones are oestrogen and progesterone in women and testosterone in men.

The process of bone loss can be speeded up by:

• natural menopause in women, when hormone levels drop
• outside influences such as treatment for cancer

Thinner, less dense bones are at more risk of breaking (fracturing). Doctors call bone thinning osteoporosis.

Bone loss and breast cancer treatment

We know from research that people having hormone treatments for breast cancer have increased bone loss compared to other people at the same age. They are at higher risk of breaking a bone.

Some breast cancer treatments aim to stop your body producing particular sex hormones or block their action. In these cases it is not possible to take hormone replacement therapy (HRT).

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.

Chemotherapy

Chemotherapy can lead to an early menopause, which can lower oestrogen levels and lead to bone loss.

Tamoxifen

Tamoxifen is a type of hormone therapy. In pre menopausal women it causes some bone loss for 1 to 2 years but not at a significant level.

But in post menopausal women tamoxifen can increase the bone density, particularly of the spine and hip bones. So it can protect the bones.

Aromatase inhibitors

Other hormone therapies used for breast cancer called aromatase inhibitors can also cause bone loss. They include:

• anastrozole
• exemestane
• letrozole

You can lose between 1% and 3% of your bone density for each year of treatment if you are past your menopause. Treatment with tamoxifen for 2 to 5 years before having aromatase inhibitors can slow down the rate of bone loss.

Younger, pre menopausal women might have aromatase inhibitors for breast cancer alongside other drugs to shut down their ovaries. In these women, the rate of bone loss is likely to be greater. This is partly because all women have some bone loss when they go through their menopause.

Stopping the ovaries from working

Some women with breast cancer have surgery to remove the ovaries. 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.

Tests for bone loss

UK guidelines recommend that women with breast cancer at high risk of osteoporosis should have their bone density measured before starting hormone treatment. Regular bone density checks should also take place during cancer treatment.

The test you have is called a DEXA or DXA scan.

Reducing the risk of bone loss

Calcium and vitamin D 

Adults should generally have 700mg of calcium a day. People with osteoporosis should aim for 1000mg a day.

Dairy products (milk, cheese and yogurt) contain calcium. Some foods have added calcium. Check food labels to see how much calcium they contain. Milk substitutes such as soya or rice milk do not contain as much calcium as dairy products.

You can also get calcium from:

• green vegetables (cabbage, broccoli and okra)
• soya products including tofu
• tinned fish with bones (sardines, salmon and pilchards)
• nuts and dried fruit
• fortified breakfast cereals 
• bread and foods made from flour 
• tap water 

Calcium supplements are available. Dietitians recomend that you do not have more than a total of 1500mg of calcium. This total calcium could come from your diet or a combination of diet and supplements. Too much calcium can cause tummy (abdominal) pain and diarrhoea.

Your body needs vitamin D to absorb calcium. Sunlight helps the body to make vitamin D. A daily short walk in natural sunlight makes enough vitamin D for most people. It is also found in margarine, oily fish and egg yolks. You should eat most foods in moderation. 

Your GP can refer to a dietitian to check that your diet has enough calcium and vitamin D to keep your bones healthy. 

Alcohol and caffeine 

Drinking alcohol increases the risk of bone loss (osteoporosis). National guidelines recommend a total of 14 units of alcohol per week. 

Caffeine can cause calcium to be lost in urine. A large study in Sweden suggests more than 4 cups of coffee a day may increase your risk of bone loss (osteoporosis).

Exercise

Exercise is important for bone health but it needs to be weight bearing exercise. This means that you are supporting your own weight with your legs and arms. This can strengthen muscle, improve posture, and could help with pain.

Many of us don’t take enough regular exercise. Bringing exercise into your daily life is the best way to make sure you get enough. Walking is good. Household activities are helpful, such as cleaning, gardening, shopping or even going up and down stairs. Or 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 in the swimming pool (aqua-aerobics) can. Walking and exercising in the pool is quite hard work because of the resistance of the water.

Don’t jog or take exercise that involves jumping if you already have osteoporosis. It puts too much strain on your bones. Take advice from your doctor or specialist nurse before starting any new type of exercise.

Medicines to help bone loss

Bones are naturally breaking down and repairing themselves continually. Hormone treatment can make bones break down faster than they are repairing themselves. This makes them weaker.

Bisphosphonates

Bisphosphonates work for post menopausal women taking a type of hormone therapy called aromatase inhibitors for breast cancer.

Bisphosphonates move calcium cells from your bloodstream into your bone. This helps to keep the bone strong. As you need to keep some calcium in your bloodstream, your doctor may give you calcium tablets.

Bisphosphonates can maintain bone strength and may also help to prevent breast cancer from spreading to the bones. Studies are looking at whether taking bisphosphonates can help people with breast or prostate cancer to live longer.

Bisphosphonates include:

• zoledronic acid (Zometa)
• ibandronic acid (Bondranat)
• disodium pamidronate (Aredia)
• 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 is a different type of drug. It works by stopping the activity of bone cells called osteoclasts. Denosumab can increase bone density to help strengthen the bone. It can be used instead of bisphosphonates to help to reduce fractures in people whose cancer has spread.

Its brand names are Prolia and Xgeva (pronounced ex-jee-va). It is a treatment for most cancers

Further information on osteoporosis

The National Osteoporosis Society has a lot of information about the causes, prevention and treatment of osteoporosis. They also have guidelines for doctors treating women with hormone therapy for breast cancer. You can access the guidelines on the National Osteoporosis Society website.