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The Relationship Between Cigarette Smoking And Thyroid Health

Published October 14 2013

There can be numerous factors which can lead to the development of a thyroid or autoimmune thyroid condition.  This includes chronic stress, intestinal permeability, infections, and numerous other factors.  But what impact can smoking cigarettes having on thyroid health?  There are a few studies which show a correlation between cigarette smoking and thyroid conditions, and I’ll discuss this in greater detail in this article.

While everyone knows that smoking is bad for their health, why is this the case?  Most people know that there is a relationship between smoking and lung disease.  And numerous studies have shown this connection (1) [1] (2) [2].  Many people don’t realize that the carcinogens in cigarette smoke affect the expression of our genes, which correlate with lung cancer (3) [3] (4) [4].  In addition to lung cancer, cigarette smoking also increases the risk of developing coronary heart disease (5) [5] (6) [6].

What Toxins Are Cigarette Smokers Exposed To?

Toxic metals are incorporated into the tobacco lamina during cultivation (7) [7], and as a result, smokers are at greater risk of exposure to heavy metals such as cadmium, lead, and thallium.  Of these, cadmium is the heavy metal most commonly associated with cigarette smoking (8) [8] (9) [9].  Cadmium is quite toxic, as it is associated with renal, neurological, skeletal, and other toxic effects, including reproductive toxicity, genotoxicity, and carcinogenicity (10) [10].  Lead is another toxin associated with cigarette smoking (11) [11].

But in addition to toxic metals, VOCs (volatile organic compounds) are another toxin associated with smoking, as one study showed that smokers displayed significantly elevated breath levels of benzene, styrene, ethylbenzene, o-oxylene, and octane (12) [12].  The same study showed that a typical smoker inhales 2 mg of benzene daily, compared to 0.2 mg/day for the nonsmoker.  Another study demonstrated that cigarette smoking is a primary source of benzene, toluene, and styrene and an important source of ethylbenzene and xylene exposure (13) [13]

How Does Smoking Affect Thyroid Health?

Numerous studies have shown a relationship between smoking and Graves’ Disease.  One study concluded that smoking is associated with Graves’ Disease, and it especially increases the risk for the development of more severe ophthalmopathy (14) [13].  The same study concluded that smoking was not associated with other thyroid diseases. Another study looked at whether stressful life events and smoking were associated with Graves’ Disease (15) [14], and did in fact find that both psychological stress and smoking were associated with Graves’ Disease in women, but not in men.  Yet another study showed that there was a significantly higher prevalence of cigarette smoking in women with Graves’ opthalmopathy and nontoxic goiter than for healthy female controls (16) [15].  And for those who have Graves’ Disease and go into remission, one study concluded that cigarette smoking increases the likelihood of Graves’ Disease recurrence in males treated with anti-thyroid drugs (17) [16].

Although I think that stress was a big factor in the development of my Graves’ Disease condition, my mother smoked two packs of cigarettes daily throughout my childhood.  So it is possible that this was a factor in the development of my condition, although I didn’t develop this condition until many years after I moved out of my parent’s house.

So it’s clear that cigarette smokers are at an increased risk of developing Graves’ Disease.  But is there any correlation between smoking and hypothyroid conditions?  Well, another toxin cigarettes contain is cyanide.  Thiocyanate is the detoxification product of cyanide, and can have a goitrogenic effect on the thyroid gland (18) [17].  One study concluded that an increase in serum thiocyanate concentration from smoking may contribute to the development of hypothyroidism in patients with Hashimoto’s Thyroiditis (19) [18]. And another study looked at the serum thiocyanate concentrations of 426 smokers and 191 non-smokers and found that the levels of serum thiocyanate were significantly higher among cigarette smokers and correlated with number of cigarettes smoked per day (20) [19].  So it is possible that cigarette smoking can have an inhibitory affect on thyroid function.

With that being said, previously I mentioned how one study concluded that smoking was associated with Graves’ Disease, but was not associated with other thyroid diseases (15) [14].  And another study actually showed that smoking lowers the risk of developing thyroid peroxidase and thyroglobulin antibodies, and subclinical and overt autoimmune hypothyroidism (21) [20].  The same study confirmed that smoking is a dose-dependent risk factor for Graves’ hyperthyroidism and especially for Graves’ ophthalmopathy.

In summary, based on the research it seems obvious that cigarette smokers are at greater risk of developing Graves’ Disease.  With regards to hypothyroid conditions, the studies are conflicting, as some studies demonstrate an increased risk of developing hypothyroidism due to the antithyroid properties of thiocyanate, while a few other studies show no correlation between cigarette smoking and hypothyroidism.  Of course since smoking consists of numerous toxins, it obviously makes sense for people to try avoiding this nasty habit.  I mentioned earlier how my mother smoked during my childhood, and she did so for about forty years before finally quitting.  And so if she were able to quit, I truly believe anyone can also do this, which not only will reduce your risk of developing lung cancer or cardiovascular disease, but just may also prevent the development of a thyroid or autoimmune thyroid condition.