All about hormones

Where do hormones come from?

Hormones in your body control specific body functions, such as metabolism, growth and reproduction. If the levels of certain hormones are too high, they can make our cells grow and divide more quickly than usual. This can increase the risk of cancer.

Natural hormones are produced by glands. These hormones made naturally by the body are called endogenous hormones.

Hormones and cancer risk

Some natural hormones can increase your chances of developing certain types of cancer. For example, the longer a woman is exposed to estrogen – even when it’s naturally occurring – the greater her risk of breast cancer. A woman who starts menstruating at a younger-than-usual age, reaches menopause later than usual or never gets pregnant has a higher risk of breast cancer because these factors increase her lifetime exposure to estrogen.

For men, long-term exposure of prostate cells to testosterone plays a role in prostate cancer development. The risk of prostate cancer increases as men grow older and their prostate cells are exposed to testosterone for a longer period.

A teenager looking at a pack of birth control pills

Synthetic hormones

Hormones can also be made in a lab. These synthetic hormones can be found in birth control pills, hormone replacement therapy and chemicals in the environment. These hormones can also raise or lower your hormone levels. It’s possible that these changes in hormone levels can increase the risk of cancer.

A teenager looking at a pack of birth control pills

How do chemicals affect your hormones?

You might have read about recent studies that have focused on a group of chemicals called endocrine disruptors. These chemicals can interfere with or disrupt your endocrine system.

What is the endocrine system?

The endocrine system is made up of several glands in the body, including the ovaries, testes, thyroid and pancreas. The endocrine system also includes cells that release hormones found in the gastrointestinal tract, kidneys, heart and placenta. Endocrine glands produce hormones.

Chemicals that are endocrine disruptors can change the way the endocrine system works by:

  • acting like certain naturally occurring hormones, such as estrogen
  • blocking the action of certain hormones
  • interfering with the production of hormones or hormone receptors
  • altering the chemical messages sent by hormones
What kinds of substances are endocrine disruptors?

Birth control pills, some cancer drugs and other medications disrupt our endocrine system on purpose – to control fertility, to treat cancer and to treat other medical conditions. 

Endocrine disruptors can also be found in synthetic chemicals used as industrial solvents and lubricants, including polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs) and dioxins. Other examples of endocrine disruptors include bisphenol A (BPA) from plastics, some flame retardants (PBDEs) and phthalates.

It’s possible that endocrine disruptors could change how hormones act in our bodies and lead to health problems, such as cancer. The evidence linking most endocrine disruptors to cancer so far has been inconsistent.