Most breast cancers need the hormone estrogen to grow and survive, and effective cancer treatments work by starving the cancer of estrogen. However, estrogen is important in maintaining bone strength and protecting bones. Reduced levels of estrogen leads to weakening of the bones and poor bone health.

There are different types of breast cancer, and around 70 per cent are sensitive to the female sex hormone oestrogen.

Women who have had breast cancer treatment before menopause might find they develop symptoms such as hot flushes, night sweats, joint aches and vaginal dryness. These are symptoms of low oestrogen, which occur naturally with age, but may also occur in younger women undergoing treatment for breast cancer. These changes are called the genito-urinary syndrome of menopause (GSM), which was previously known as atrophic vaginitis.