Hormones are naturally produced substances in the body that tell some cells and tissues how to behave and grow. Hormone therapy (also called endocrine therapy) aims to stop or slow the growth of certain types of cancer that use hormones to grow. These include breast, prostate and thyroid cancers.
Hormone therapy is typically given in combination with other treatments. It may be used to make a tumour smaller before surgery (neo-adjuvant therapy), reduce the risk of cancer returning after surgery (adjuvant therapy), and to control or slow the growth of cancer cells that have spread around the body (metastasised) and cannot be cured (palliative therapy). Hormone therapy might also be used to reduce or prevent some symptoms of prostate cancer in men who cannot have surgery or radiation therapy.
Types of hormone therapy
There are 2 main categories of hormone therapy – therapies that stop the production of hormones that cause cancer growth, and therapies that change how these hormones behave.
Hormone therapy can:
- be taken orally as a pill or tablet
- be injected into a large muscle, such as the thigh or arm (intramuscularly)
- be injected or implanted under the skin, usually in the thigh or belly (subcutaneously)
- involve surgically removing hormone-producing organs or glands.
Oral hormone therapy can be taken at home. Injections are usually given at a clinic, hospital or in your doctor’s office. Surgical treatment will require a hospital stay.
Hormone therapy can be given for some types of cancer to:
- reduce the level of hormones in the body, such as oestrogen in women with breast cancer
- suppress the function of an organ that produces the hormone
- block the production of hormones
- stop the effect of hormones on the growth of cancer cells
- prevent the release or effect of additional hormones that stimulate androgens (called chemical castration), which are used in the treatment of prostate cancer.
Side effects of hormone therapy
Consequences of hormone therapy will depend on which hormones are given. Side effects may include:
- hot flushes
- night sweats
- headaches
- nausea and vomiting
- skin rashes
- increased risk of blood clots and stroke
- increased risk of some heart conditions
- cataracts
- changes in mood
- loss of libido
- joint pain
- loss of bone density
- loss of strength.
Additionally, in women, side effects may also include:
- vaginal dryness
- disrupted menstrual cycles
- onset of menopause
- breast tenderness
- increased risk of endometrial (uterine) cancers.
For more information about hormone therapy and its side affects you should talk to your doctor or visit Treatment side effects.