Autoimmune disorders can affect almost any part of the body, but the thyroid is especially susceptible. Dr. L. Saranac and colleagues at the University Clinical Center, Nis, Serbia, provided a review.
“The incidence of chronic autoimmune thyroiditis (CAT) and Graves' disease (GD) has increased dramatically over the past few decades, afflicting up to 5% of the general population,” they reported.
As with most autoimmune conditions, women are affected more often than men. Genetic factors put some people at risk.
However, there are also environmental factors that we can control. Saranac described the effects of iodine, selenium, tobacco smoke, infectious diseases, certain drugs, and physical and emotional stress.
Iodine.
There is a narrow range of iodine intake that is optimum for thyroid health. Since the thyroid hormones T4 and T3 contain iodine, the thyroid will not be able to produce sufficient amounts if there is an iodine deficiency in the diet.
However, too much iodine can be just as bad. Autoimmune thyroid disease is rare in countries with low iodine intake, and increases in parallel with increased iodine in the diet. The mechanism is not yet understood.
Selenium.
A deficiency of selenium in the diet is associated with autoimmune thyroid disease. Patients with celiac disease are especially susceptible because their ability to absorb selenium is impaired.
Environmental pollutants.
Tobacco smoke and polychlorinated biphenyls (PCBs) are the primary chemical agents associated with autoimmune thyroid disease.
Infections.
Infectious agents are suspected as the trigger for many autoimmune conditions.
Yersinia enterocolitica is the pathogen most strongly associated with thyroid disease.
Drugs. Amiodarone, used to treat heart conditions, and lithium, used to treat psychiatric conditions, have the most pronounced effect on thyroid function.
Stress.
There is some association between autoimmune thyroid disease and stress, both psychological and physical.
Dr. Paolo Marzullo and colleagues in Italy reported a strong association between autoimmune thyroid disease and obesity. It is not completely clear which one causes the other, since weight gain is one of the symptoms of low thyroid function.
However, Marzullo concluded that obesity also increases susceptibility to autoimmune attack on the thyroid. The hormone leptin, which is produced by adipose tissue, plays a key role in the mechanism.
References:
1. Saranac L et al, “Why is the thyroid so prone to autoimmune disease?” Horm Res Paediatr 2011; 75: 157.
http://www.ncbi.nlm.nih.gov/pubmed/21346360
2. Marzullo P et al, “Investigations of thyroid hormones and antibodies in obesity: Leptin levels are associated with thyroid autoimmunity independent of bioanthropometric, hormonal, and weight-related determinants”, J Clin Endocrinol Metab. 2010; 95(8): 3965.
http://www.ncbi.nlm.nih.gov/pubmed/20534769
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.
Reviewed September 27, 2011
by Michele Blacksberg RN
Edited by Jody Smith