The extent of the widespread damage to health caused by cigarette smoke is almost unbelievable. Smoking kills 60% of people who don’t quit, and cigarette smoke affects almost every organ system in the human body. People are familiar with the most common problems caused by smoking, like cancers, emphysema, and heart disease. There is less awareness about the impact of smoking on things like vision, diabetes, cholesterol, wound healing, immune diseases, arthritis, to name just a few.
I thought a discussion about some of the less well known health effects from smoking might be of interest. As there has been some discussion in the community about smoking and the thyroid, we can start there.
The thyroid is a gland that produces hormones which help regulate general metabolism and blood pressure, heart rate, body temperature, and weight. Thyroid hormones are critical for growth, reproduction, development of nerve cells, and regulation of energy. Underproduction of these hormones (hypothyroidism), or overproduction (hyperthyroidism) are relatively common problems which can cause serious health problems. You can find an overview of the thyroid and associated problems.
Smoking has multiple effects upon the thyroid. Some of the reported effects on the thyroid are strongly supported by research, while the research on other effects is somewhat ambiguous. Reasons for the ambiguity include the fact that there are many different compounds in cigarette smoke, different studies employ different methods to measure cigarette smoking, and studies on the effect of smoking are conducted with different populations such as those with thyroid disease or general populations without disease.
There is strong and unambiguous evidence that smoking increases a person’s risk for Graves disease (a condition causing goiter and over activity of the thyroid), and will increase the likelihood and severity of thyroid related eye disease (Graves disease can be a cause for bulging eyes that can become severe enough to threaten vision). In addition, children who have been exposed to cigarette smoke have a significantly higher risk for Graves disease and eye related conditions, as do women who are pregnant. Stopping smoking seems to reduce the risk and complications from Graves disease, although former smokers do continue to be at higher risk, but more research with consistent measures of ‘former’ smoker are needed.
The association between smoking and enlarged thyroid is strongly supported by evidence, especially among women. Smoking is also found to have especially damaging effects on the thyroid among people who are iodine deficient. A number of studies have found that smoking increases the risk of under-active thyroid among people with Hashimoto’s disease (which is the most common cause of hypothyroidism in the United States). However other studies have not found this association.
Unrelated to illness, smokers tend to have lower levels of thyroid specific hormones. Studies are a bit ambiguous on the effects of stopping smoking on hormone levels, but most of the evidence supports a return to normal after smoking cessation, although the time to return to normality is unclear.
Bottom line, is for some people smoking can cause thyroid damage and dysfunction. Stopping smoking can help. People who have thyroid symptoms after stopping smoking, should continue not to smoke and talk with their health care provider.
I would be interested in your comments and feedback, including your thoughts on the level of detail in a blog like this. Ideally we would like to strike a balance between providing information that is generally accessible and describing varied and sometimes complex research findings. Let us know your thoughts, and here’s to a tobacco free future!