Bone loss and sex hormones

Some cancer treatments lower the amount of sex hormones in the body. These hormones are oestrogen and progesterone in women and testosterone in men. Low levels of sex hormones can sometimes cause changes to the bones.

Our bones are at their strongest around the age of 35. As we age they gradually become thinner and weaker. This is the same for men and women. For most people it is not a problem and doesn’t cause any symptoms. But the process 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.

We know from research that people having hormone treatments for breast and prostate cancer have increased bone loss. They are at higher risk of breaking a bone. In these situations, you cannot usually take hormone replacement therapy (HRT) to control bone loss. Some breast or prostate cancer treatments aim to stop your body producing particular sex hormones or block their action. So it is not possible to take replacement sex hormones, which is what HRT is.

If you are having breast or prostate cancer treatment it makes sense to talk to your specialist about whether you have a risk of bone weakening. If you do, there are steps you can take to help keep your bones healthy. If you are a woman at risk of bone weakening your specialist may suggest you start taking drug treatment.

It is important to remember that while your treatment may have side effects, it is also helping to control your cancer, or reducing the chance of it coming back. Of course, that is very important for your health.

Any treatment that lowers oestrogen levels in women can increase the risk of bone loss. Treatments that cause osteoporosis include

• Chemotherapy leading to an early menopause
• Hormone therapy with drugs called LH blockers (for example, Zoladex)
• Hormone therapy with drugs called aromatase inhibitors (such as anastrozole, exemestane or letrozole)
• Radiotherapy to your ovaries, which stops them making hormones
• Surgery to remove your ovaries before menopause

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.

Other hormone therapies used for breast cancer called aromatase inhibitors can also cause bone loss. Women past their menopause having this treatment lose between 1% and 3% of their bone density for each year of treatment. Treatment with tamoxifen for 2 to 5 years before having aromatase inhibitors may slow down the rate of bone loss.

Younger, pre menopausal women may 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.

UK guidelines recommend that women with breast cancer at high risk of osteoporosis should have their bone density measured before they start hormone treatment. They should also have regular bone density checks during their cancer treatment. The test you have is called a DXA scan (some doctors and nurses pronounce this as dexa scan). There are no guidelines for men at the moment but it is likely that if you are at high risk of osteoporosis you will have a scan.

In men with prostate cancer, bone loss is caused by treatments that lower testosterone levels in the body. These treatments include

• Hormone therapy with drugs called LH blockers (for example, goserelin (Zoladex)
• Hormone therapy with drugs called anti androgens (e.g. cyproterone acetate, flutamide)
• Surgery to remove the testicles (orchidectomy)

In men the extent of bone loss is less clear than in women. Results from studies seem to vary with some showing no change. Others show about a 5% loss of bone after a year of treatment. The spine is most likely to be affected. A few studies show that bone loss levels off after a year of treatment. Research looking at men who had hormone therapy for at least 10 years found that all men had some bone loss but the extent varied from person to person.

There are several ways you can help to lower your osteoporosis risk

• Make sure you get enough calcium in your diet
• Cut down on caffeine and alcohol because these can interfere with calcium levels
• Don’t smoke as it increases osteoporosis risk
• Make sure you take enough exercise to build up your bones
• In some cases doctors may suggest drug treatment for bone loss
  

Calcium in your diet

An average adult should have about 700mg of calcium every day for good bone health. There is no evidence to suggest that people with cancer need any extra calcium. If you already have osteoporosis, more calcium may help – between 1,000 and 1,200mg a day.

Our main dietary source of calcium is dairy products. If you eat a normal, balanced diet including dairy foods, you are unlikely to be short of calcium. But some women with breast cancer don’t like to eat dairy foods. 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 that includes the bones (sardines, salmon and pilchards)
• Nuts
• Dried fruit
• Fortified breakfast cereals
• Bread and other foods made from flour

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. Milk substitutes such as rice milk, oat milk and soya milk may also have added calcium – check the label.

You could take supplements instead of calcium rich foods. Dieticians recommend that you don’t take more than the amount you should have in a normal diet. Too much calcium can be harmful. The Food Standards Agency says that taking up to 1,500mg a day is unlikely to do any harm.

For your body to use calcium, you also need vitamin D. Your body needs sun to make vitamin D. If you like being outside, then you probably get enough sun during the summer months to give you enough vitamin D for a year. But if you are out in the sun, remember to protect against skin cancer with sunscreen. There is added vitamin D in margarine. It’s also found in oily fish and egg yolks.

You may want to ask your specialist or specialist nurse to refer you 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.

Caffeine and alcohol

Some research suggests that if you drink more than 4 cups of coffee a day and don’t have much calcium in your diet it may slightly increase your risk of osteoporosis. Caffeine increases the loss of calcium in urine. Drinking alcohol is also thought to increase osteoporosis. So limiting the amount of alcohol you drink will help to lower your risk of developing it. Women should not drink more than one small drink a day and men only two.

Exercise and bone health

Exercise is important for bone health. But it has to be weight bearing exercise. Swimming doesn’t help because your bones are not supporting your weight. If you already take part in sport, that’s great. But many of us don’t take enough regular exercise. The best way to start to tackle this is to try and bring exercise into your daily life. 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 very good for you. 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. The most important thing is that you get into the habit of exercise, however you choose to do it.

If you already have osteoporosis, don’t jog or take exercise that involves jumping because it puts too much strain on your bones. Take advice from your doctor or specialist nurse before starting any new exercise.

Drugs called bisphosphonates can prevent or slow bone loss. We know from trials that they can help postmenopausal women taking aromatase inhibitors and men taking hormone therapy for prostate cancer. Your doctor will take into account your own bone density levels and risk of further loss of bone density when deciding whether you need to start bisphosphonate treatment.

Women who have had an early menopause and are taking aromatase inhibitor therapy are most likely to benefit from bisphosphonates.

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.

There are several different types of bisphosphonates, including

• Zoledronic acid (Zometa)
• Ibandronic acid (Bondranat)
• Disodium pamidronate (Aredia)
• Sodium clodronate (Bonefos, Loron)

You have clodronate and ibandronate either as a tablet or through a drip into a vein (an infusion). You have zoledronic acid and pamidronate through a drip. You can find out more about having these drugs, and their particular side effects, by using the links above for each drug. You can also take a weekly bisphosphonate tablet for osteoporosis. This is called aledronate (Fosamax).

Bisphosphonates can cause side effects, such as an upset stomach and flu like symptoms. They can also affect the way your kidneys work.

Research is looking at other treatments that may help to reduce fractures. One of these is the monoclonal antibody denosumab. It works by stopping the activity of bone cells called osteoclasts. Denosumab can increase bone density and reduce the number of fractures for some types of cancer including with secondary bone cancer from breast cancer. NICE have issued guidance saying that denosumab should be available for people with secondary bone cancer from breast cancer and other solid cancers when doctors may also be considering bisphophonates as a treatment within the NHS in England and Wales. They said there was not enough evidence at the moment to recommend it for secondary bone cancer from prostate cancer. You can find out how you have denosumab and its possible side effects in the cancer drugs section.

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.