What are hormones?

Hormones are substances made naturally in the body. They act as ‘messengers’ that tell organs or tissues to carry out various functions.

What are hormone receptors?

Breast cells contain special proteins called hormone receptors. These receptors ‘receive’ messages from hormones in the body and respond by telling the cells what to do.

What is oestrogen receptor positive (ER+) breast cancer?

Oestrogen is a hormone that plays an important role in the female reproductive system. It helps to control functions such as the menstrual cycle.

Sometimes breast cancer cells contain oestrogen receptors. This is called oestrogen receptor positive (ER+) breast cancer.

When oestrogen receptors are found in breast cancer cells, this can stimulate the breast cancer to grow. If your breast cancer is ER+, you may be offered hormone (endocrine) therapy. A number of hormone therapies work in different ways to block the effect of oestrogen and slow down the growth of breast cancer.

How will I know if my breast cancer is ER+?

All invasive breast cancers are tested for oestrogen receptors using tissue from a biopsy or after surgery. If your cancer is oestrogen receptor positive, your specialist will discuss with you which hormone therapy they think is most appropriate.

What are progesterone receptors?

Sometimes tests are also done for progesterone (another hormone) receptors.

The benefits of hormone therapy are less clear for people whose breast cancer is only progesterone receptor positive (PR+ and ER-). Very few breast cancers fall into this category, but if this is the case your specialist will discuss with you whether hormone therapy is appropriate.

If your cancer is hormone receptor negative, then hormone therapy will not be of any benefit.

Find out more about hormone therapy »

Last reviewed: February 2018
Next planned review begins 2020

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