Cigarette Smoking and Thyroid Disease

The Cause-and-Effect Dangers of Lighting Up

Man smoking
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There is no single organ system of the body where cigarette smoking is anything less than harmful. While we often focus on the effects of smoking on the lungs, heart, and skin, the thyroid gland can be hurt just as much by the simple act of lighting up.

This is especially true for persons with thyroid disease in whom smoking has a cause-and-effect relationship: on the one hand, increasing the risk of disorders like Graves' disease while worsening the symptoms related to hypothyroidism and Hashimoto's disease.

Smoking and Thyroid Damage

Tobacco smoke contains substances that affect both the function of the thyroid and the gland itself. One of these components is cyanide which, when smoked, is converted to an anti-thyroid agent called thiocyanate. Thiocyanate is known to inhibit with the absorption of iodine into the thyroid which, in turn, lowers the production of hormones needed to regulate the liver, muscles, and other organ systems.

In person diagnosed with hypothyroidism (low thyroid function), this only complicates symptoms (fatigue, weight gain, mood swings) and takes back many of the gains afforded by treatment. The persistent inflammation can also result in the enlargement of the gland itself, which is of particular concern to people living with Graves' or Hashimoto's disease:

  • Grave's disease, a form of hyperthyroidism characterized by thyroid enlargement (goiter), occurs twice as frequently in smokers than non-smokers. Moreover, in persons living with the disease, smoking is associated with faster disease progression, the deterioration of symptoms, and a poorer response to thyroid treatment.
  • The relationship of smoking and Hashimoto's disease, an autoimmune disorder linked to hypothyroidism, is not as clearly defined. What do know, however, is that smoking appears to further diminish thyroid function while spurring the development of goiters, particularly in iodine-deficient individuals.

    Smoking and Eye Problems

    One of the more profound effects of smoking is its impact on vision, most predominantly in people with Graves' ophthalmopathy (a condition characterized by swollen, bulging eyes).

    One study conducted in 2014 concluded that smokers with Graves' disease were more likely to experience rapid eye deterioration, including the development of double vision, the constriction of eye movement, and irreversible optic nerve damage.

    More concerning yet is the fact that treatment of Graves' ophthalmopathy (traditionally with steroids and radioiodine) is seen to be four times less effective in smokers than in non-smokers.

    Smoking and Thyroid Cancer

    Thyroid cancer is today the eighth most common cancer in women. While it may seem logical to assume that smoking is a risk factor, as it is with lung and throat cancer, studies thus far have been largely contradictory.

    One study released in 2012 reported that, among 331 postmenopausal women with thyroid cancer, there was absolutely no difference in the rate disease between women who smoked or those who didn't smoke. In fact, the study suggested that smokers had a modest reduction in cancer risk, a result that the investigators themselves admitted was "disquieting."

    Other studies have since mirrored the results, albeit more in differentiated (mature) cancers than undifferentiated (immature) cancer. As such, it is possible that smoking may have a greater impact on a developing tumor than an existing one.

    A Word From Verywell

    Whatever perceived benefits cigarettes offer pales in comparison to the benefits of stopping. In the end, there is no overlooking the fact that smoking will only worsen thyroid symptoms, speed the progression of your disease, and make your thyroid treatment all the less effective. And, while some might assume that it's okay to smoke you have thyroid cancer ("because it can't make it worse"), think again.

    Smoking may not impact the tumor itself, but it can increase the risk of metastasis, spreading the cancer beyond the site of the tumor to other parts of the body.

    Most insurance plans today offer free smoking cessation treatment as part of their annual benefits. If you have trouble kicking the habit, speak with your doctor about pharmaceutical options that may help.

    Sources:

    Kabat, G.; Kim, M.; Wactawski-Wende, J.; and Rohan, T. "Smoking and alcohol consumption in relation to risk of thyroid cancer in postmenopausal women." Cancer Epidemiol. 2012; 36:335-40.

    Sawinka-Gutaj, N.; Gutaj, P.; Sowinski, J.; et al. "Influence of cigarette smoking on thyroid gland - an update." Endo Pol. 2014; 65(1):54-62.

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