Hormone Therapy: The Basics
What are hormones and how are they used as therapy?
Hormones are chemicals that are naturally produced by the organs that make up the body's endocrine system (the pancreas, and the pituitary, thyroid, and adrenal glands). These chemicals travel throughout the body through the bloodstream, helping carry out the different jobs of various organs in the body. Hormones regulate just about every cell in the body. Some examples of hormones include: estrogen, testosterone, insulin, thyroid hormone, cortisol, and epinephrine.
Researchers have found that some cancers are "fueled" by hormones, and may depend on them to grow. In these cases, blocking the action of these hormones could possibly stop the cancer from growing. There are a few ways in which this can happen:
- Block the hormones from acting: Cells have "receptors" on their surface that certain hormones connect to and trigger activity inside the cells. By blocking the receptor with another compound, the hormone is not able to connect to its receptor. So if the hormone's normal "parking spot" on the cell is already taken, the hormone cannot attach to and activate the cell.
- Prevent the body from producing the hormone: This can be done with medication to block production of the hormone, or with surgery to remove the organ that produces it. For example, estrogen production can be significantly decreased by surgically removing the ovaries.
- Eliminate the hormone receptors on cells or change their shape: This makes it impossible for the hormone to properly attach itself to the cell receptor and to activate it, essentially making the hormone unable to function.
Hormone therapy that is used to treat certain cancers should not be confused with hormone replacement therapy. Hormone therapy is used to block hormones or their actions, whereas hormone replacement therapy, which is not a cancer treatment, usually refers to giving hormones to replace the ones the body no longer makes in order to treat menopause-related symptoms.
How is hormone therapy given?
Hormone therapy is most often used to treat breast and prostate cancers, where its role is well established through numerous clinical trials. Meanwhile, research is ongoing to study the potential use of hormonal therapy in treating other cancer types. Hormone therapy can be given in a few ways:
- Oral medication – some therapies are taken by mouth.
- Injection – some therapies are given by an injection under the skin (subcutaneous) or in the muscle (intramuscular).
- Surgical intervention – for example, removal of the ovaries in women, or testicles in men, results in decreased production of certain hormones.
Many patients think of hormone therapy as being "less potent" than chemotherapy, but it can be just as effective in certain breast and prostate cancers. Hormone therapy is considered a "systemic" therapy, meaning that it travels throughout the body. Surgery and radiation therapy are considered "local" treatments.
What are the side effects of hormone therapy?
The side effects are caused by the lack of whatever hormone is being blocked or inactivated. For women, these effects are similar to those experienced with menopause, which is the body's natural decline in estrogen production with age. Side effects can include: hot flashes, night sweats, weight gain, vaginal dryness, and headache. Some side effects are caused by the hormone therapy. These can include: nausea, hair loss or thinning, muscle aches and joint pain, and, more seriously, blood clots and increased risk of uterine/endometrial cancer.
This decrease in the body's natural hormones can put men and women at higher risk for developing osteoporosis. Bisphosphonate therapy may be used to counteract this side effect. In addition, your healthcare provider may recommend taking steps to decrease the risk or severity of osteoporosis. This may include increasing calcium and vitamin D intake through diet or supplements, participating in weight-bearing exercise and avoiding tobacco and alcohol use (which increases osteoporosis risk). Learn more about bone health and cancer.
How do I know if hormone therapy is working for me?
This answer varies, depending on the type of cancer being treated. Many patients will have radiology studies (CT scans, MRI scans, PET scans) every so often to see how the tumor is responding (shrunk, stayed the same, or grown). Some types of tumors can be followed using a specific "tumor marker.” This is a substance that is either produced directly by the tumor, or by the body in response to the tumor, and can be measured by a blood test. If the therapy is working, one would expect the tumor marker level to decrease. In some cases, a decrease in a patient's symptoms may be able to signal if the medications are shrinking the tumor or not. Talk with your healthcare provider about your specific situation.
Classes of Hormone Therapy
An antiestrogen or estrogen blocker works by blocking estrogen receptors in breast tissue. While estrogen may not actually cause breast cancer, it is necessary for the cancer to grow in some breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.
Estrogen receptor antagonist
Every person reacts differently to medications, so it is hard to predict what side effects each patient will have. However, the most common side effects in this category of medications include hot flashes, night sweats, weight gain, vaginal dryness and nausea. Blood clots and endometrial cancers are rare, but can occur with these medications.
In women who have gone through menopause, estrogen is mainly made by converting androgens (sex hormones produced by the adrenal glands) into estrogens. An enzyme called aromatase is responsible for this conversion. Aromatase inhibitors block this conversion, leading to less estrogen in the body.
Every person reacts differently to medications, so it is hard to predict what side effects each patient will have. However, common side effects in this category of medications include hot flashes, night sweats, headache, nausea, hair thinning, vaginal dryness, muscle aches, and joint pain.
Other Hormone Treatments Used for Breast Cancer
Hormone-sensitive breast cancers can also be treated with other hormone agents.
Androgen, works by opposing the activity of estrogen
A form of progesterone, works by interfering with cell growth in ER+ cells.
LHRH agonist, works by stopping production of leutinizing hormone by the pituitary gland. LH causes the ovaries to make estrogen.
Most prostate cancers need supplies of the male hormone testosterone to grow. Testosterone is an androgen made by the testes and adrenal glands. The production of testosterone can be stopped by surgically removing the testicles or through medication therapy. Anti-androgens work by blocking testosterone receptors, and preventing testosterone from attaching to these receptors found in the prostate cancer cells. Without testosterone, the cancer cells may either grow more slowly or stop growing altogether. You may hear this treatment called androgen deprivation therapy or ADT.
Every person reacts differently to medications, so it is hard to predict what side effects each patient will have. However, the common side effects for this category of medications include hot flashes, breast tenderness, nausea, loss of sex drive and impotence.
Luteinizing Hormone Releasing Hormone Agonist (LHRH Agonist)
A hormone called luteinizing hormone, made by the pituitary gland, stimulates the testicles to produce testosterone. LHRH agonists stop the production of luteinizing hormone by the pituitary gland. This reduces the production of testosterone in men. The cancer cells may then grow more slowly or stop growing altogether. These are sometimes called gonadotropin-releasing hormone blockers (GnRH blockers). You may hear this treatment called androgen deprivation therapy or ADT.
Every person reacts differently to medications, so it is hard to predict what side effects each patient will have. However, common side effects in this category of medications include tiredness, breast tenderness, nausea, loss of sex drive, and impotence.
If hormone therapy is part of your treatment plan, talk with your care team about which medications or surgeries may be right for you.