Bone loss and osteoporosis on aromatase inhibitors

Oestrogen helps keep bones strong by slowing the natural breakdown of old bone. Aromatase inhibitors, such as letrozole, anastrozole and exemestane, lower oestrogen to very low levels to protect against breast cancer returning, so bone is lost faster than usual. Over years this can lead to osteopenia or osteoporosis, and a higher chance of fractures, particularly of the spine, hip and wrist. The risk can be measured with a bone density scan and reduced with exercise, calcium and vitamin D, and, when needed, bone-strengthening medicines.

Who is at higher risk

Women who already have low bone density, are older, have had a previous fracture, are thin, smoke, drink heavily, take steroid tablets, or went through menopause early. Women who have had ovarian suppression before an aromatase inhibitor also lose bone more quickly.

How bone health is checked

A DEXA bone density scan before starting, and repeated every one to two years depending on the result, shows how your bones are changing. Blood tests may check vitamin D, calcium and other causes of bone loss.

When bone medicines are advised

If the scan shows significant bone thinning, or you have other risk factors or a previous fracture, your team may recommend bisphosphonates such as zoledronic acid or alendronate, or denosumab injections.

Bone loss on aromatase inhibitors is real and worth taking seriously, but it is also one of the most manageable side effects. With monitoring and, when needed, bone medicines, most women complete their hormone therapy without a fracture.

Bone medicines have benefits beyond bones

In postmenopausal women with early breast cancer, bisphosphonates have also been shown to slightly lower the chance of cancer returning in the bones, which is one reason some oncologists recommend them more widely.

Bone medicines have side effects too

Flu-like symptoms after a first infusion, stomach upset with tablets, low calcium, and rarely jaw bone problems can occur. A dental check before starting is usually advised.

Bone often recovers after stopping

Bone density tends to improve somewhat after aromatase inhibitors are completed, though not always fully.

What this page cannot tell you

It cannot tell you whether you need a bone medicine. Ask your team to explain your scan and risk factors.

A rare but important side effect of bone-strengthening medicines is osteonecrosis of the jaw, where an area of jaw bone does not heal properly, often after a tooth extraction.

Why dental care matters

The risk is higher with poor dental health, dental infections or extractions during treatment. Having a dental check and any needed work before starting reduces it.

During treatment

Brush and floss well, see your dentist regularly, and tell every dentist that you take a bone medicine. Avoid extractions if possible, and discuss any planned dental surgery with your oncology team first.

Warning signs

Report jaw pain, swelling, loose teeth, numbness in the jaw or exposed bone in the mouth promptly.