Does Smoking Cessation Cause Hypothyroidism?

Woman applying a nicotine patch
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You may be one of the people who first notices your symptoms of thyroid disease or are first diagnosed with a thyroid condition after you quit smoking cigarettes. This phenomenon makes some people think that smoking cessation may be a cause of thyroid disease. But the question is, is it? Is there a link?

Tobacco and the Thyroid

Tobacco smoke contains a number of chemicals and toxic substances that affect the function of your thyroid gland.

Studies have shown that cigarette smokers are more likely to have thyroid enlargement (goiter), and it is possible that mild thyroid enlargement in smokers could be a sign of subtle thyroid disturbance.

Some research suggests that cigarette smokers are twice as likely as nonsmokers to develop Graves' disease and that smoking worsens eye problems in people with Graves' disease. Smoking also interferes with the effectiveness of treatment for thyroid-related eye problems.

One study suggests that that cigarette smoking may increase the risk of hypothyroidism in patients with Hashimoto's thyroiditis. Results from another study suggest that cigarette smoking is associated with so many abnormalities that affect the thyroid that it is unlikely that it has just one single effect on your thyroid gland.

In women with hypothyroidism, studies suggest that smoking decreases both the thyroid's ability to release thyroid hormones, as well as the effectiveness of the thyroid hormones.

The study results did not, however, definitively prove that smoking causes hypothyroidism, rather, that smoking increases the severity and effects of hypothyroidism.

How Does Smoking Affect Thyroid Secretion or Action?

One component of tobacco smoke is cyanide, which is converted to thiocyanate, which inhibits iodide uptake and hormone synthesis.

There are many other components of smoke that might have antithyroid action, too.

The most dramatic effect of smoking on the thyroid is its association with Graves' disease, especially those hyperthyroid patients who also have Graves' ophthalmopathy. Whether smoking predisposes a person to Graves' hyperthyroidism is unclear.

Finally, smoking is also linked to the development of autoimmune thyroiditis.

Smoking Cessation, Weight Gain, and Hypothyroidism

Researchers have yet to establish a clear and direct causal relationship between stopping smoking and hypothyroidism. This makes it a controversial and conflicting topic in the medical world. What we do know, however, are the following two important points:

  • The risk of developing hypothyroidism increases six-fold within 2 years of smoking cessation.
  • Studies have shown that levels of thyroid antibodies increase after smoking cessation.

One interesting hypothesis links smoking cessation to hypothyroidism and weight gain. Specifically, the premise is that when you quit smoking, the weight gain that often accompanies smoking cessation may actually be attributable to the appearance of and failure to treat your hypothyroidism.

What Does All This Mean?

First, an important cautionary message.

Don't interpret an association between smoking cessation and hypothyroidism as an excuse to continue smoking. It is misguided to think that continuing to or resuming smoking will somehow prevent, reverse, or resolve your hypothyroidism. If you smoke, you must stop. Smoking is not only bad for your thyroid, but is also damaging to your lungs, heart and entire body.

Instead, the association between smoking cessation and hypothyroidism should increase your awareness of possible hypothyroid symptoms (for example, cold intolerance, fatigue, dry skin, weight gain, hair loss, constipation, and depression, among others).

At the same time, this link should also raise your awareness that if you are or formerly were a smoker, you may be at increased risk for hypothyroidism. It is a good idea to have your physician regularly check your thyroid after you quit smoking, especially if you have a family history of thyroid disease.

Is It Time to Quit? 

Every day is a good day to quit smoking. If you want to explore resources that can help you quit, you will want to read Verywell's  many helpful and informative articles about smoking cessation.


Abstract titled "Weight Gained after Cessation of Smoking May Be Caused by Onset of Hypothyroidism" by JH Mestman published in Clinical Thyroidology in 2012.