If you have celiac disease, you also have a higher risk of autoimmune thyroid disease. Up to 10% of people with celiac disease have an autoimmune thyroid condition, a far higher rate than in the general population, studies show. Meanwhile, between 1.5% and 6.7% of people with autoimmune thyroid disorder also have celiac disease.
It's likely that the two conditions share common genetic origins and underlying mechanisms. Celiac often appears with other autoimmune diseases, especially type 1 diabetes, rheumatoid arthritis, and autoimmune liver disease.
Science hasn't yet pinpointed the cause of autoimmune diseases, but some researchers theorize that an environmental trigger might jump-start the disease process in genetically susceptible people.
Although it's far from proven, at least one medical study suggests the environmental trigger for thyroid disease could be gluten. Celiac disease patients who adopt a gluten-free diet may reduce their chances of developing autoimmune thyroid disorder, according to that study, indicating gluten intake in gluten-sensitive individuals might trigger thyroid disease.
Types of Autoimmune Thyroid Disorder
In people with an autoimmune disease, the body's own white blood cells mistakenly attack organs or other types of tissue. The white blood cells attack the lining of the small intestine in celiac disease. With autoimmune thyroid disorder, the white blood cells attack the thyroid gland, which is a small, butterfly-shaped gland in your throat that controls your body's metabolism.
Autoimmune thyroid disorder can cause your thyroid gland to become either overactive (Graves disease) or underactive (Hashimoto's disease).
In Graves disease, the thyroid pumps out too much of the hormones thyroxine, known as T4, and triiodothyronine, or T3. Women over age 20 have the highest risk for the condition, but men also are at risk. Overactive thyroid symptoms include insomnia, irritability, weight loss, heat sensitivity and muscle weakness. Graves disease patients also may develop bulging eyes and a noticeable goiter.
In Hashimoto's disease, meanwhile, the thyroid produces too little T3 and T4. Low thyroid symptoms include fatigue, weight gain, weakness, sensitivity to cold, aching muscles and stiff joints, constipation and facial swelling. Again, women have a higher risk for the disease than men.
Gluten Connection in Autoimmune Diseases?
In the study suggesting that treating celiac disease with a gluten-free diet can lessen the risk of developing an autoimmune thyroid disorder, a group of Italian researchers compared the incidence of celiac disease in healthy people, in autoimmune thyroid patients, and in a group of "sick patients" with non-autoimmune thyroid disease, cancer and heart disease.
The prevalence of celiac disease in the thyroid disease group was "significantly greater than in both healthy and sick control groups," the researchers wrote. Genetic and environmental factors could be to blame, they said, but added "it is also possible that the association between celiac disease and autoimmunity in untreated celiac patients is caused by the gluten intake."
Other studies have shown that organ-specific antibodies - i.e., antibodies indicating that the body's white blood cells are attacking specific organs, such as the thyroid gland - disappear after three to six months on the gluten-free diet.
It's possible, the researchers wrote, that "undiagnosed celiac disease can cause other disorders by switching on some as yet unknown immunological mechanism." If that's true, then strict compliance with the gluten-free diet could reduce the risk of celiac disease patients developing additional autoimmune disorders, including autoimmune thyroid disease. The study was published in Digestive Diseases and Sciences in February 2000.
AGA Doesn't Recommend Universal Celiac Disease Screening
The Italian research team suggested that all autoimmune thyroid disease patients could benefit from screening for celiac disease. However, there's disagreement in the medical community over whether such screening truly is necessary.
The American Gastroenterological Association Institute, in a 2006 statement on diagnosis and management of celiac disease, noted that patients with autoimmune thyroid disease are at higher risk for celiac, but added that "there is no compelling rationale for the routine screening of patients with thyroid disease for celiac disease in the absence of symptoms suggesting or compatible with celiac disease."
Instead, the institute suggested that clinicians screen autoimmune thyroid disease patients who also have symptoms that suggest celiac disease.
American Gastroenterological Association (AGA) Institute. "AGA Institute Medical Position Statement on the Diagnosis and Management of Celiac Disease." Gastroenterology 2006;131:1977-1980
American Gastroenterological Association (AGA) Institute. "Medical Position Statement on the Diagnosis and Management of Celiac Disease." Gastroenterology 2006;131:1977-1980 http://www.gastrojournal.org/article/S0016-5085(06)02226-8/pdf
Chin Lye Ch'ng, M. Keston Jones, MD, and Jeremy G. C. Kingham, MD. "Celiac Disease and Autoimmune Thyroid Disease." Clinical Medicine and Research 2007 October; 5(3): 184-192.
Graves' Disease. Consumer Information Sheet. National Endocrine and Metabolic Diseases Information Service. Accessed: June 5, 2010. http://www.endocrine.niddk.nih.gov/pubs/graves/
Hashimoto's Disease. Consumer Information Sheet. National Endocrine and Metabolic Diseases Information Service. Accessed: June 5, 2010. http://www.endocrine.niddk.nih.gov/pubs/Hashimoto/
Peter Elfström, Scott M. Montgomery, Olle Kämpe, Anders Ekbom, Jonas F. Ludvigsson. "Risk of Thyroid Disease in Individuals with Celiac Disease." Journal of Clinical Endocrinology & Metabolism. doi:10.1210/jc.2008-0798