Celiac disease is an autoimmune disorder that causes inflammation and damage in the lining of your intestine when you eat gluten, a protein found in wheat, rye, and barley. Perhaps not surprisingly in light of the fact that they both have an autoimmune component, an obvious relationship has been found between autoimmune thyroid disease (AITD) and celiac disease.

The Risk Relationship

Research has found that your risk of celiac disease is substantially higher when you already have AITD (Hashimoto's thyroiditis or Graves' disease). Conversely, when you have celiac disease, you're more than four times more likely to have AITD.﻿﻿ Given these risks, some experts recommend that patients with AITD should be routinely screened for celiac disease and vice versa.﻿﻿

AITD and celiac disease have a few commonalities, including sharing some of the same genes, the presence of antibodies in both conditions, a higher risk for other autoimmune conditions, and even some of the same symptoms.﻿﻿

Shared Genes

While it's still unclear exactly why celiac disease and AITD often occur together, at least some of the explanation seems to be that they share specific genes. The gene variants that make you more susceptible to developing autoimmune endocrine diseases like AITD, DR3–DQ2 and/or DR4–DQ8 are the same ones that predispose you to celiac disease. Other specific genes, including CTLA-4, the HLA genes, and PTPN22, are all found in celiac disease and AITD as well.

Many people have the DR3–DQ2 and/or DR4–DQ8 gene variants and never go on to have either celiac disease or AITD, indicating that other factors are involved in developing these conditions as well.

Higher Risk of Other Autoimmune Diseases

As is typical with autoimmune disorders, people with celiac disease and/or AITD are also more likely to develop other autoimmune conditions, like type 1 diabetes, Addison's disease, rheumatoid arthritis, lupus, Sjögren's syndrome, and autoimmune hepatitis. The older you get, the more this risk increases.

Shared Symptoms

Celiac disease also shares some symptoms with both forms of AITD, Hashimoto's thyroiditis (HT) and Graves' disease (GD).

Celiac Disease Symptoms Weight loss

Fatigue

Constipation and diarrhea

Joint pain

Depression and/or anxiety

Hair loss

Infertility

Miscarriage HT and GD Symptoms Weight loss (GD)

Fatigue (both)

Constipation (HT); diarrhea (GD)

Joint pain (HT)

Depression (HT); anxiety (GD)

Hair loss (both)

Infertility (both)

Miscarriage (both)

Antibodies

Another similarity between the two is the presence of antibodies. In celiac disease, about 98 percent of patients have tissue transglutaminase (tTG) IgA antibodies in their blood and an estimated one-fifth have thyroid and/or type 1 diabetes antibodies.﻿﻿

Various studies on the prevalence of tTG IgA antibodies in people with AITD have found that the rate is around 2 percent to 5 percent in general. This translates to roughly 4 percent in adults and nearly 8 percent in children.﻿﻿

Interactions Between Thyroid and Gluten

Studies show that celiac disease and/or gluten may affect how your thyroid functions. For instance:

The tTG antibodies found in celiac disease may contribute to thyroid dysfunction by binding to thyroid cells.

If you have celiac disease along with a mild form of hypothyroidism called subclinical hypothyroidism, following a strict gluten-free diet for a year may bring your thyroid hormone levels back to normal.

The Role of a Gluten-Free Diet

Research is unclear as to whether or not implementing a gluten-free diet is helpful when you have AITD but not celiac disease. Experts do note that eliminating gluten can help reduce inflammation in your gut, a problem for many AITD patients.

However, some studies have shown that thyroid antibodies, which are common in AITD, decrease after implementing a gluten-free diet. For instance, in a 2018 study, 34 women with AITD were divided into two groups; one was put on a gluten-free diet and the other was not. After six months, the women on the gluten-free diet had reduced levels of thyroid antibodies while the other group had no noticeable change.﻿﻿

In some cases, even though you have many of the symptoms of celiac disease, your tests for it may not turn out positive. If your symptoms resolve by going on a gluten-free diet, this condition is called non-celiac gluten sensitivity (NCGS), non-celiac wheat sensitivity (NCWS), or more broadly, gluten intolerance or sensitivity.

Gluten sensitivity has similar symptoms to celiac disease, but the antibodies found in celiac aren't present. As with celiac disease, it's unclear what causes this sensitivity, but it also appears to cause an autoimmune reaction and possibly intestinal damage.

Gluten-Free Diet Benefits

If you're diagnosed with celiac disease, your doctor will treat it by putting you on a lifelong gluten-free diet. In the case of non-celiac gluten sensitivity, a gluten-free diet will also benefit you; however, unlike with celiac disease, it's possible that you'll be able to retest your sensitivity after a year or two and reintroduce gluten into your diet.

Going on a gluten-free diet can have these benefits:﻿﻿

It helps your intestines heal, allowing better absorption of your thyroid hormone replacement medication.

You may eventually need less of your medication due to better absorption.

There's the potential for weight loss.

Your celiac disease symptoms like fatigue, weight loss, constipation, diarrhea, joint pain, depression, and anxiety will likely decrease.

You may feel healthier overall.

Your thyroid inflammation may be reduced.

Your body may be able to better absorb nutrients.

Talk to Your Doctor Don't ever start a gluten-free diet without your doctor's approval since there could be risks for your individual health status.

Gluten-Free Diet Drawbacks

Though some people eliminate gluten for weight loss and other purposes, little research has been conducted on whether or not a gluten-free diet is a good choice for those who don't have celiac disease or gluten sensitivity.

Disadvantages of a gluten-free diet include:﻿﻿

Gluten-free foods tend to be more expensive.

You're no longer getting many of the vitamins and nutrients found in gluten like calcium, iron, folate, thiamin, and fiber, so you'll have to get them in other foods and/or by taking supplements.

It can be difficult to follow.

You need to read labels carefully, both to avoid gluten and to make sure you're not getting too much sugar or fat, which tends to replace gluten in some products.

A Word From Verywell

If you think you may have symptoms of celiac disease or a gluten sensitivity, talk to your doctor about getting tested. Even if you don't have either of these, cutting down on the amount of gluten you eat or trying a low-FODMAP diet, especially if it seems like your thyroid symptoms aren't responding well to treatment, may help.