ARCHIVED CONTENT: Harvard Medical Press provides access to our library of archived content to serve our readers. Note the date each article was published or last reviewed. No content on this site, regardless of date, should be taken as a substitute for direct medical advice from your physician or other qualified practitioner.
Breast cancer is the most commonly diagnosed cancer among women in the United States, and thyroid disorders affect millions of American women. Most breast cancers are sensitive to hormones such as estrogen, and researchers believe that thyroid hormones have estrogen-like effects. So for years, scientists wondered if too much thyroid hormone might play a role in breast cancer. A new study suggests the answer may be “yes.”
It’s all about the thyroid gland
The thyroid gland is a butterfly-shaped gland located at the base of the neck that produces thyroid hormones. Thyroid hormones affect almost every cell in the body and have many important functions, including controlling metabolism, heart rate, and body temperature.
Some people have hyperthyroidism, or an overactive thyroid, in which the thyroid gland produces too much thyroid hormone. It can cause weight loss, thinning hair, sweating, anxiety, and an increased heart rate. Women have 5-10 times more thyroid activity than men.