Knowledge means less uncertainty during your journey with breast cancer. For women facing hormone therapy, the amount of research available is endless. There is a lot of talk about hormones, estrogen, and plenty of other things happening inside of your body, but when it comes to the science of breast cancer, there’s a fine line between helpful and confusing. Let’s breaking down the science behind the most common types of hormone therapy.
First, What are hormones?
Understanding your hormones starts with understanding your endocrine system. Made up of organs such as your pancreas, ovaries, thyroid and adrenal glands, your endocrine system produces hormones that are released into the bloodstream and signal to other parts of the body.
So what do these hormones do? Think of them as chemical messengers that give instructions to the different cells in your body. For example, T3 and T4 hormones regulate your body temperature, metabolism and heart rate, while estrogen from your ovaries controls sexual development in women. Estrogen is also produced in other tissues such as fat cells, liver, and adrenal glands and also plays a role in cholesterol levels, affects bone density and brain function and can impact your heart, skin and other tissues in both men and women. Hormones are responsible for lots of different things, including that awkward mustache your friend grew in 8th grade and physical changes like puberty.
So How Do Hormones Affect Cancer?
Hormones bind to specific receptors found on normal cells; however, cancer cells can also express these receptors to drive their growth. These cancers are considered “hormone sensitive.”
When your body releases hormones, they flow through your bloodstream until finding their specific cell receptors to bind to. Each hormone corresponds with a different receptor, like keys made for a single lock. For example, when estrogen binds to its receptor on a breast cancer cell, it will unlock a signal for the cell to grow and multiply. There are two major hormones that can fuel breast cancer growth: estrogen and progesterone. Your doctor will likely tell you whether you are estrogen receptor-positive (ER+ breast cancer) or progesterone receptor-positive (PR+ breast cancer).
About 80% of all breast cancers are considered ER+. Of these, approximately 65% are also PR+.
How does Hormone Therapy Work?
Your therapy will depend on the receptor status of the breast cancer cells and whether or not you’ve been through menopause. Doctors will either try to prevent hormone production, or block the receptors from receiving the hormones they need to grow.
The first type of hormonal therapy for women with ER+ breast cancer, works by blocking estrogen from reaching cancer cells, this class of drugs is called selective estrogen receptor modulators (SERMs). Tamoxifen is the most commonly used SERM, which works by binding to the estrogen receptors in place of estrogen in the breast cancer cells. Tamoxifen is a form of “anti-estrogen” therapy and is prescribed for both pre- and post-menopausal women.
The benefit of using SERMs is that they are selective. This means that Tamoxifen blocks estrogen’s action specifically in breast cells but can activate estrogen’s action in other cells, such as bone, liver, and uterine cells.
The second type of hormonal therapy centers on stopping the body from producing estrogen all together. These medications are called Aromatase Inhibitors. They work by inhibiting the function of the enzymes that lead to the production of estrogen. Typically postmenopausal women are prescribed these medications.
“But wait,” you’re asking. “I thought women don’t produce estrogen from their ovaries after menopause? So what’s the point?”
And you’re right. But other glands such as your adrenals, liver, and fatty tissue, will continue producing estrogen after menopause. Aromatase Inhibitors aim to suppress the production of estrogen in these estrogen producing organs.
Hormone therapy is a large topic, and there are other less-common treatments for women with hormone sensitive breast cancer. But for the sake of simplicity, this article focused on the two most common treatment paths and hopefully clarified some things. It is always encouraged to bring up any questions with your doctor.