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The Gluten-Thyroid Connection

The surprising link between your thyroid and celiac disease.

Kara Smith had a hard time losing the baby weight after the birth of her son in 2002. No matter how much sleep she got, she was always exhausted. But more troubling to the usually articulate marketing professional was that she seemed to be struggling to find words and couldn’t remember simple things.

“I’d have a two-item grocery list and couldn’t remember either one,” she says. “If I weren’t 31, I would’ve thought it was Alzheimer’s.”

Doctors assured her that she was just tired, that this was typical for new mothers.

“But I’d see other mothers who didn’t get any sleep and they seemed happy and functioning well enough,” says Smith of Tucson, Arizona.

A few years earlier, Smith’s mother had been diagnosed with hypothyroidism (a disorder where the thyroid doesn’t produce enough hormones). Could I have it, too, Smith wondered?

A blood test showed Smith’s thyroid was indeed sluggish. Further testing revealed low levels of a key thyroid hormone, T4, as well as antibodies to the thyroid. Her doctor diagnosed Hashimoto’s thyroiditis, an autoimmune disease where antibodies attack the thyroid, eventually destroying it. Treatment involves replacing the T4 hormone. Patients often start with a low dose of T4—a pill taken each morning—and adjust as necessary.

“I felt better immediately on a small amount of thyroid medication,” says Smith. “I got my vocabulary back overnight.”

The treatment also seemed to ease the constipation Smith had dealt with for years. But after a while, things leveled out. Although her doctor tweaked her hormone dose every six weeks, her fatigue persisted and her hormone levels wouldn’t normalize.

Several years later, still unhappy with her thyroid treatment, Smith developed a blistering rash on her arms and legs that stumped dermatologists. Steroid pills and antihistamines tamped down the rash enough to make it tolerable but they didn’t clear it.

Eventually Smith sought help from a naturopath who suggested the rash could stem from a gluten problem.

“The first month on the gluten-free diet, the rash wasn’t better but it wasn’t worse,” she says. “The second month, it started to improve. That’s when I knew it was DH and that I had celiac disease.”

Similar Symptoms

Dermatitis herpetiformis, DH for short, is the skin manifestation of celiac disease. People with DH have celiac disease and must adhere to a lifelong gluten-free diet. (Blood tests for celiac disease may or may not be positive because they detect damage in the gut, not the skin. Some individuals with DH have no intestinal involvement and no gastrointestinal symptoms.)

By the time Smith discussed DH with her dermatologist, her skin was too clear (thanks to the gluten-free diet) to do a skin biopsy to confirm a diagnosis. However, her doctor agreed all signs pointed to DH. The fact that she had Hashimoto’s thyroiditis was one of those signs.

DH is closely linked with autoimmune thyroid issues. Studies show that up to 30 percent of individuals with DH also have thyroid abnormalities. Likewise, high rates of thyroid disease—mostly Hashimoto’s but also Graves’ disease—have been shown in celiac disease. Hashimoto’s is the most common cause of hypothyroidism in the United States while Graves’ disease accounts for the majority of cases of hyperthyroidism. Both are autoimmune disorders.

“People with one autoimmune disease have a tendency to develop others,” says Jeffrey Garber, MD, chief of endocrinology at Harvard Vanguard Medical Associates and past president of the American Association of Clinical Endocrinologists. “We see thyroid problems in those with celiac disease more often than in the general population and the reverse is also true. One doesn’t imply the other but the risks go up.”

Either disease can come first. Smith suspects trouble with gluten actually came first in her case.

“Looking back, I had lots of stomach problems as a child,” she recalls. “In my 20s, I was on reflux medication but it never worked.”

Bostonian Lisa Hill, 54, has a similar story. She was diagnosed with Hashimoto’s in her early 30s and celiac disease at age 47.

“I’m the runt in my family—smaller than everyone and, at least before my celiac diagnosis, I was sicker, too,” she says. “I’m sure celiac disease actually hit first.”

Not long after Hill’s celiac diagnosis, she began to question: Was the fatigue, joint pain and anemia she had suffered over the years the result of her thyroid or celiac disease—or both?

Many symptoms of thyroid and celiac disease closely overlap—fatigue, gastrointestinal issues, unexplained weight changes, anemia and low mood or depression. In both diseases, symptoms often start gradually over the course of months or even years. Women are disproportionately affected, and, in the case of Hashimoto’s and celiac disease, their typical age of onset also overlaps. It peaks in the middle decades.

Despite this, routine screening for thyroid problems in those with celiac disease (and vice versa) isn’t called for by the American Thyroid Association or the American Gastroenterological Association. However, both physician groups acknowledge the strong celiac-thyroid link.

“Thyroid disease is relatively common in the general population but it’s significantly increased in celiac disease,” says Daniel A. Leffler, MD, director of clinical research at the Celiac Center at Beth Israel Deaconess Medical Center. Leffler checks thyroid hormone levels when celiac disease is diagnosed and every two to three years thereafter. If there’s reason for concern, he checks at more frequent intervals.

Likewise, Jeffrey Garber, MD, keeps celiac disease on his radar.

“Celiac disease should be considered or looked for in anyone with autoimmune thyroid disease who has persistent gastrointestinal complaints despite good control of their thyroid disease,” he says. “Additionally, if patients are taking their medication correctly but it’s still hard to control their thyroid, that is, levels vary a bit, consider screening for celiac disease.”

Gaining Control

Before Lisa Hill’s celiac diagnosis, her thyroid hormone levels were always fluctuating. Since going gluten-free, she’s had an easier time stabilizing her thyroid hormones, as well as managing symptoms of Sjogren’s, an autoimmune disease discovered shortly before her celiac diagnosis. Sjogren’s affects the moisture-producing glands, causing dry eyes and mouth.

“It feels like the gluten-free diet cooled everything off for me,” Hill says. “The problems are still there—I still need eye drops and my thyroid medication—but they’ve gotten easier to manage.”

After a celiac diagnosis, controlling thyroid disease often becomes easier as patients absorb their thyroid medication more readily, says Reed Larsen, MD, head of the thyroid section in the Division of Endocrinology at Brigham and Women’s Hospital. Once on the gluten-free diet, some people with celiac disease even require less thyroid medication.

But that doesn’t mean the thyroid condition is improving. A recent study compared thyroid function at the time of celiac diagnosis and one year later and noted no improvement after treatment with the gluten-free diet.

“Just like the pancreas in type-1 diabetes, once thyroid function is gone, it generally doesn’t come back,” says Leffler. “The dose may decrease due to better absorption but most patients are on hormone replacement for life.”

It has been shown that thyroid antibodies sometimes disappear in those with celiac disease, once they’re treated with the gluten-free diet, but these people probably didn’t have established thyroid disease, says Peter H.R. Green, MD, director of the Celiac Disease Center at Columbia University. Having thyroid antibodies indicates a higher risk for developing thyroid disease but thyroid function may still be normal, he explains. “Apart from celiac disease, we don’t think treatment with the gluten-free diet alters the course of established autoimmune diseases.”

Whether the diet impacts the development of future autoimmune diseases has been hard to prove or disprove, says Leffler. One often-cited Italian study showed that the earlier the diagnosis, the fewer number of autoimmune conditions, suggesting an earlier celiac diagnosis is protective. But a second study contradicted these findings.

“The problem is we don’t know when people actually get celiac disease,” says Leffler. “We only know when they were diagnosed or maybe when they developed symptoms.”

There is, however, some tantalizing evidence that untreated celiac disease could play a role in triggering thyroid disease. Using thyroid tissue from rats, Green and colleagues showed that the main antibody in celiac disease, tissue transglutaminase (tTG), can bind to thyroid tissue. tTG has been shown in separate research to bind to bone and heart tissue, possibly contributing to osteoporosis and cardiomyopathy, both of which are linked to untreated celiac disease.

Still, Green calls the potential for tTG to set up the conditions for thyroid disease to develop “just a possibility.” Celiac experts agree the strongest line of evidence for the co-occurrence of thyroid and celiac disease is that both disorders share a genetic risk.

Mood Matters

Dietitian Cheryl Harris, RD, knows about celiac and thyroid disease. Many of her clients have the double diagnosis and so does she. For Harris, the celiac diagnosis came first and Hashimoto’s was discovered two years later.

“Having both diseases can be extremely draining,” she says. “Both can sap your energy, cause GI problems and set off mood issues.” She’s seen clients sent to psychiatrists before discovering they had undiagnosed celiac disease, thyroid disease or both.

Internist Adrienne Clamp, MD, who practices in Northern Virginia, says low mood is common in thyroid and celiac diseases and she attributes it to flagging energy levels and just not feeling well. Clamp herself has hypothyroidism, although not the autoimmune kind.

“I know when my thyroid isn’t well controlled, my nerves are frayed and I feel like I can’t handle one more thing,” she says. “I’d characterize it as feeling less resilient.”

Low mood may get better once underlying causes like celiac or thyroid are properly treated but it can also occur independently from celiac or thyroid disease. In those cases, it’s unlikely to resolve, says Harris, who underscores that persistent low mood and depression should be treated by a licensed mental healthcare professional.

In recent years, Harris has seen an uptick in individuals without celiac disease who wonder if the gluten-free diet can help with thyroid symptoms like low mood or weight gain.

“The gluten-free diet is widely discussed in the thyroid community,” she says, “but there has been little published research to date about this.”

“A lot of things affect the way you feel and how you absorb thyroid hormones,” says Daniel Leffler, MD. “Even outside of celiac disease, if you dramatically change your diet, you may dramatically change the way you feel and the amount of thyroid hormone you need to take.”

Leffler says it’s not clear there’s any link between thyroid disease and non-celiac gluten sensitivity. “There isn’t any evidence that non-celiac gluten sensitivity is autoimmune, so you wouldn’t expect it to be associated with other autoimmune diseases like autoimmune thyroid disease.” But, he adds, the question hasn’t been specifically addressed by researchers.

Harris stresses that those interested in the gluten-free diet should get tested for celiac disease before they embark on the diet. (Celiac testing requires regular gluten consumption in order to be accurate.)

“If people believe they’re just sensitive to gluten, they may cheat on the gluten-free diet because they don’t think there are real consequences,” she says.

Slow But Steady

Thyroid hormone acts very slowly in the body. It can take several months for symptoms to ease and doses may need to be adjusted. Too little thyroid hormone can lead to other health problems, including high cholesterol. Too much hormone can cause heart problems and bone loss.

Healing from celiac disease also takes time. When intestinal damage is severe, it may be a year or more before symptoms resolve and nutritional deficiencies reverse.

Big improvements for Lisa Hill didn’t happen overnight. “I had to be very patient with my body,” says Hill, who’s been managing celiac and thyroid disease for eight years.

Kara Smith is newer to the double diagnosis. She’s been gluten-free close to two years. Although she continues to deal with some fatigue and brain fog, she’s optimistic that her health will continue to improve.

“Going gluten-free cleared the road,” she says. “Gluten exacerbated all my symptoms. If I was tired or constipated or had a headache, it was ten times worse on gluten.”

“Careful attention to the gluten-free diet is key for those managing both celiac and thyroid disease,” sums up Reed Larsen, MD. “The gluten-free diet helps protect against complications of celiac disease and ensures thyroid medication is absorbed,” he says.

“With these bases covered, the outlook is very good,” agrees Jeffrey Garber, MD. For the past 30 years, Garber has been treating a patient with celiac disease, Hashimoto’s and type-1 diabetes. “She’s managed them very well over the years,” he says. She just turned 91.

Senior medical correspondent Christine Boyd lives in Baltimore, Maryland.