Last year, I posted a request the Usenet newsgroup alt.support.thyroid for for anecdotal information from other women who, like me, were diagnosed hypothyroid after stopping smoking. I stopped smoking in July of 1995, and it was the same time that my thyroid went haywire. |
I received a large number of responses from women who said they'd experienced this, and were interested in more information. 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, The Bridge, Spring 1993, Vol. 8, No. 1, titled "Smoking and the Thyroid," by David S. Cooper, M.D., F.A.C.P. You can request a copy of this article by calling the Foundation at 617-726-8500.
The article said that 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. According to that article, smoking also apparently worsens eye problems in people with Graves' disease.
One study also suggests that that smoking may increase the risk of hypothyroidism in patients with Hashimoto's thyroiditis. (Journal 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, -- says 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. In women with hypothyroidism, smoking decreases both thyroid secretion and thyroid hormone action. But, the study results do not indicate that smoking causes hypothyroidism, only that it 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; decrease the binding of triiodothyronine to its receptors or its post-receptor actions in the liver, muscle, or other organs; or both.
The most dramatic effect of smoking on the thyroid is its association with Graves' hyperthyroidism, and especially with Graves' ophthalmopathy. Whether smoking precedes Graves' hyperthyroidism (with or without ophthalmopathy) or not, there are more smokers than would be expected among those with these conditions.
While I don't have an answer as to whether or not stopping smoking "triggers" problems with the thyroid -- as it anecdotally often appears to be -- it is clear that medical researchers have found that smoking can worsen hypothyroidism in people that already have it, and smoking can seriously affect thyroid function.
I also believe that smoking/nicotine creates an artificially high metabolism that masks the fatigue/lethargy commonly seen in hypothyroidism. When the smoker quits, this masking is removed, and the full effects of hypothyroidism on the metabolism and thyroid are felt.
And, for smokers with undiagnosed thyroid dysfunction, without proper thyroid hormone treatment, stopping seems to be a metabolic/weight gain double whammy, as they lose the appetite suppressant, metabolism-upping effects of nicotine, and experience the full effects of the hypothyroidism.