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How Does Estrogen Impact Cancer?

Published by Connealy, MD on June 6, 2024

How Does Estrogen Impact Cancer?

Estrogen is an important sex hormone produced primarily by the ovaries, testes, fat tissue, and adrenal glands. This hormone regulates the growth, development, and physiology of the human reproductive system. It also influences neuroendocrine, skeletal, adipose, and cardiovascular systems.

While estrogen is essential for normal physiological processes, such as menstrual cycles and pregnancy, excessive or prolonged exposure to estrogen can contribute to the development of certain types of cancer, particularly hormone-sensitive cancers like breast, uterine, and prostate cancers. This is due several mechanisms:

Cellular Proliferation  

Estrogen is often considered the hormone of ‘new life.’ It plays a significant role in regulating cell growth and division. It is higher in women to facilitate the growth of breast tissue in puberty, the growth of the endometrium each month during the menstrual cycle, and to support pregnancy. In hormone-sensitive tissues like breast, uterine, brain, and adipose tissues, estrogen binds to receptors and initiates cell growth and proliferation. If a cell becomes sick and cancerous and estrogen is already chronically elevated in the body, the hormone can promote uninhibited growth and contribute to the development of cancer.


Estrogen’s ability to mimic hypoxia, a condition of low oxygen levels in the body, creates an environment that fosters tumor growth and development. Estrogen can induce changes in cells’ ability to use oxygen, promoting the Warburg effect. This is a metabolic shift that enhances cancer cell survival and proliferation. Estrogen can also trigger cellular responses similar to those seen in low oxygen environments. This can cause cellular stress and lead to processes like angiogenesis, where new blood vessels form to supply tumors with nutrients and oxygen.


Estrogen orchestrates the growth of new blood vessels. The hormone prompts cells to produce vascular endothelial growth factor (VEGF), a protein that signals blood vessel growth. This process, known as angiogenesis, contributes to cancer progression by providing tumors with essential oxygen and nutrients, aiding their growth and spread. The increased blood supply can also facilitate the escape of cancer cells into the bloodstream, leading to metastasis and the formation of new tumors.


Estrogen influences immune cells, affecting the body’s inflammatory responses. By modifying how these cells communicate and react to signals, estrogen can intensify inflammation. It directly regulates the production of pro-inflammatory cytokines, proteins that control immune cell activity. These cytokines, in turn, can fuel cancer by fostering chronic inflammation, creating an environment conducive to tumor development, spread, and aggressiveness.

What causes high estrogen?

  • Exposure to endocrine disrupting chemicals and xenoestrogens
  • Low/imbalanced progesterone
  • Poor liver function
  • Hormone therapy & hormonal birth control 
  • Obesity
  • Poor digestion & gut health
  • High stress levels
  • Low testosterone
  • Copper toxicity & exposure to heavy metals
  • Low thyroid function 
  • Certain medications

How can we promote healthy estrogen levels?

  • Ensure adequate progesterone and testosterone levels
  • Limit exposure to endocrine disrupting chemicals, heavy metals, and toxins
  • Improve digestion and gut health
  • Ensure adequate thyroid levels
  • Improve liver function
  • Decrease stress
  • Prioritize sleep
  • Increase intake of soluble fiber
  • Prioritize a healthy weight

Bio-Identical HRT

Estrogen is an essential hormone. Many women do need to take estrogen during menopause. However, it is important that it is also taken with bio-identical progesterone. Progesterone counters its toxic effects and ensures estrogen levels are healthy. We want everything to be in balance!

Unfortunately, today we are exposed to estrogens in the environment and many men and women have elevated levels. Personal care and cleaning products, plastics, flax, soy, and industrial chemicals can have estrogenic effects when they are consumed or come in contact with the skin. On top of this, many of us experience high stress in our day to day lives. Stress can decrease progesterone in women and testosterone in men, both of which are needed to keep estrogen in check. Ensuring levels are balanced is an essential component of prevention and treatment. 

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