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Cigarette Smoking and Thyroid Disease

The Relationship Between Smoking and Thyroid Disease

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Updated June 09, 2014

Man smoking
Michael Savage Photography/Moment Open/Getty Images
When it comes to cigarette smoking and thyroid disease, there are three major questions that many patients have:
  • What is the relationship between smoking and thyroid disease?
  • Is it worse to smoke if you have thyroid disease? and
  • Is it a coincidence that a diagnosis of hypothyroidism sometimes comes not long after quitting smoking?
Let's take a look at the answers.

Back in 1996, I posted a request at the Usenet thyroid newsgroup for anecdotal information from other women who, like me, were diagnosed as being hypothyroid after stopping smoking. (I stopped smoking in July of 1995, and it was not too long after that I was diagnosed with my thyroid condition. That caused me to explore the relationship between thyroid disease and smoking.)

I received a large number of responses from women who said they'd had the same experience: they were diagnosed with hypothyroidism not long after stopping smoking, and were interested in more information. At that time, I contacted the Thyroid Foundation of America with these questions, and they indicated that some research had been done on the relationship between smoking and the thyroid. They sent me an article from their newsletter that outlined some of the research. Here is a recap of some of the findings.

Smoking Definitely Damages the Thyroid

First, tobacco smoke contains substances that affect the function of the thyroid. Studies show that smokers are more likely to have thyroid enlargement, and it is possible that mild thyroid enlargement in smokers could be a sign of subtle thyroid disturbance. According to a Jan. 27, 1993 article in the Journal of the American Medical Association smokers are twice as likely as nonsmokers to develop Graves' disease. Smoking also apparently worsens eye problems in people with Graves' disease.

Smoking Increases the Risk and Severity of Thyroid Disease

One study also suggested that that smoking may increase the risk of hypothyroidism in patients with Hashimoto's thyroiditis. (Jo urnal of Endocrinology Investigation1996 Oct;19(9):607-612, "Relationship between cigarette smoking and hypothyroidism in patients with Hashimoto's thyroiditis").

Also, a journal article "Cigarette Smoking and the Thyroid," The New England Journal of Medicine -- October 12, 1995 -- Volume 333, Number 15, -- reported that smoking is associated with so many abnormalities of thyroid function that it is unlikely it has just one single effect on the thyroid gland.

The study results, however, did not indicate that smoking causes hypothyroidism, only that it increases the severity and effects of hypothyroidism.

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