Which thyroid medication is gluten-free?

Quick Answer

The most common gluten-free thyroid medications are levothyroxine (Synthroid, Levoxyl, Unithroid, Tirosint), liothyronine (Cytomel), and natural thyroid hormones (Armour Thyroid, Nature-Throid, Westhroid). Levothyroxine and liothyronine are synthetic thyroid hormones, while natural thyroid hormones contain T4 and T3 derived from animal thyroid glands. Individuals with celiac disease or gluten sensitivity should avoid thyroid medications containing gluten from wheat, barley, rye or oats. Always check with your pharmacist or doctor to verify the exact ingredients and gluten-free status of any medication.

What is Gluten?

Gluten is a group of proteins found in grains like wheat, barley, rye and oats. For most people, gluten does not cause any problems or adverse health effects. However, for those with celiac disease or non-celiac gluten sensitivity, gluten triggers an abnormal immune response that damages the small intestine. Even tiny amounts of gluten in medications can cause issues for those who are gluten-sensitive.

Celiac disease is an inherited autoimmune disorder that affects about 1% of the population worldwide. When people with celiac disease eat gluten, it triggers immune system damage to the small intestine, leading to an inability to absorb nutrients from food. Non-celiac gluten sensitivity (NCGS) is a milder condition that causes digestive symptoms when gluten is ingested. The prevalence of NCGS is estimated to be around 6-7% of the population.

Why Avoid Gluten in Thyroid Medications?

Here are some key reasons why those with celiac disease or gluten sensitivity need to avoid gluten in thyroid medications:

  • Prevents damage and inflammation in the small intestine – Gluten exposure triggers an autoimmune reaction in the small intestine for those with celiac disease, leading to villous atrophy and inability to absorb nutrients. Even small amounts of gluten in medications can contribute to this intestinal damage.
  • Reduces medication malabsorption – If the small intestine is damaged by gluten, oral medications may not be properly absorbed. Gluten-free thyroid drugs help prevent malabsorption.
  • Controls thyroid drug allergy symptoms – Some individuals may develop allergic reactions to gluten-containing thyroid medications. Using gluten-free versions can eliminate allergic responses.
  • Avoids false positives on celiac testing – Consuming gluten before celiac disease testing can lead to inaccurate negative results. Strict adherence to a gluten-free diet is required for accurate testing.
  • Improves thyroid drug efficacy – Absorption and efficacy of thyroid medications may be improved by eliminating dietary gluten sources, including from drugs.
  • Alleviates NCGS symptoms – Abdominal pain, bloating, diarrhea and other symptoms of non-celiac gluten sensitivity can flare up if gluten is ingested.

For people with celiac disease and gluten sensitivity who take thyroid medication, choosing gluten-free drug options can help manage their conditions and prevent complications.

Common Types of Thyroid Medications

There are several major types of prescription thyroid medications used to treat hypothyroidism, hyperthyroidism, thyroid cancer and goiter:

  • Levothyroxine (Synthroid, Levoxyl, Tirosint, Unithroid) – Synthetic thyroxine (T4), used to treat hypothyroidism. Considered gluten-free.
  • Liothyronine (Cytomel) – Synthetic triiodothyronine (T3), can be used alone or with levothyroxine. Gluten-free.
  • Natural thyroid hormones (Armour Thyroid, Nature-Throid, Westhroid) – Contains T4 and T3 derived from the thyroid glands of pigs. Typically gluten-free.
  • Thiamazole (Methimazole) – Prevents thyroid hormone production, used to treat hyperthyroidism. Contains gluten.
  • Propylthiouracil (PTU) – Also prevents thyroid hormone synthesis. May contain gluten as excipient.
  • Potassium iodide – Inhibits thyroid hormone release. Can be gluten-free if no excipients.
  • Lugol’s solution – Contains iodine, used to treat thyroid storm or before thyroid surgery. Gluten status unknown.

The most frequently prescribed thyroid drugs are levothyroxine, liothyronine and natural thyroid hormones. These are available in gluten-free versions from major manufacturers. Older thyroid medications like PTU and thiamazole often contain gluten. Check labels carefully or contact the maker to verify gluten content.

Are Synthetic Thyroid Hormones Gluten-Free?

The most commonly prescribed thyroid medications are synthetic versions of the hormones T4 (levothyroxine) and T3 (liothyronine). Popular brand names for gluten-free levothyroxine include Synthroid, Levoxyl, Unithroid and Tirosint.

Levothyroxine is considered gluten-free by the major pharmaceutical companies that manufacture these products, including AbbVie, Pfizer, and Merck. It is typically formulated without any gluten-containing excipients or ingredients derived from gluten sources. The official prescribing information for Synthroid, Levoxyl and Unithroid indicates these contain no cereal/gluten.

Synthetic T3 liothyronine drugs like Cytomel are also regarded as gluten-free by the manufacturers. However, it is still advisable to check with your pharmacist to verify the gluten content of any formulation of levothyroxine or liothyronine, since inactive ingredients may vary. Different generics and dosage forms could potentially contain undisclosed gluten.

Liquid, capsule and tablet forms of synthetic T4/T3 thyroid drugs are widely available as gluten-free options. Intravenous solutions also avoid gluten exposure. For the most sensitive individuals, Tirosint gel capsules provide a highly purified levothyroxine sodium proven free of gluten protein residues.

Are Natural Desiccated Thyroid Drugs Gluten-Free?

Natural desiccated thyroid drugs like Armour Thyroid, Nature-Throid, and Westhroid contain a mix of T4 and T3 derived from the thyroid glands of pigs. These are considered hypoallergenic and gluten-free by the manufacturers.

According to the prescribing details, Armour Thyroid does not contain wheat, gluten, or any ingredients derived from gluten-containing cereals. Testing has not detected any gluten peptides in the final product. The maker of Westhroid and Nature-Throid, RLC Labs, states their porcine thyroid extracts contain no excipients derived from gluten-containing grains.

However, those with celiac disease or NCGS should still exercise caution with natural thyroid products. Even if no gluten ingredients are added, cross-contamination is possible during manufacturing. Checking with your pharmacist is wise to verify gluten levels in any particular product lot or pill bottle.

Which Hyperthyroidism Drugs Are Not Gluten-Free?

Two common medications used to treat hyperthyroidism are thiamazole (Methimazole) and propylthiouracil (PTU). Unlike synthetic thyroid hormones, these drugs potentially contain gluten as excipients:

  • Thiamazole – Commonly contains gluten as an inactive ingredient, according to the prescribing information. Brand names include Tapazole and Methimazole.
  • Propylthiouracil (PTU) – May contain gluten-based ingredients, but gluten content is not always disclosed. Some formulations have tested positive for gluten residues.

Hyperthyroidism is overactivity of the thyroid gland, resulting in excess T4 and T3 production. Thiamazole and PTU work by blocking the organification of iodine, which prevents synthesis of thyroid hormones.

People with celiac disease should avoid using thiamazole or propylthiouracil due to the likelihood of gluten exposure. Alternative hyperthyroid medications like potassium iodide or beta-blockers may be used instead. Checking with your pharmacist about gluten content in hyperthyroidism drugs is advised.

Other Factors to Consider with Thyroid Medications

Aside from the active drug ingredients, consider these other potential sources of gluten exposure in thyroid hormone medications:

  • Excipients – Binders, fillers, preservatives and other inactive ingredients may contain gluten. Manufacturers are not required to disclose all excipients.
  • Dosage form – Tablets and capsules more often contain excipients than liquid or injectable products.
  • Cross-contamination – Can occur during manufacturing if equipment is shared with gluten-containing drugs.
  • Generic drugs – Inactive ingredients in generics may differ from brand name versions.
  • Testing limitations – Gluten immunologic test kits can detect proteins down to 5-10 ppm, but do not guarantee zero gluten.

To avoid uncertainty about gluten content, medications formulated without any excipients are preferable for those with celiac disease or gluten intolerance. Synthetic thyroid hormones like Tirosint, which has no fillers or binders, help minimize gluten risks. Consulting your pharmacist or prescribing doctor is important to select the optimal thyroid medication for your individual needs and sensitivities.

Levothyroxine and Liothyronine Gluten-Free Options

Here are some specific prescription products containing the synthetic thyroid hormones levothyroxine and liothyronine that are verified gluten-free by the manufacturers:

Brand Name Generic Name Formulation Manufacturer
Synthroid Levothyroxine Tablets AbbVie
Levoxyl Levothyroxine Tablets, capsules King Pharma
Unithroid Levothyroxine Tablets Jerome Stevens Pharma
Tirosint Levothyroxine Capsules, liquid IBSA Institut Biochimque
Cytomel Liothyronine Tablets King Pharma

These represent some of the most widely prescribed brands of synthetic T4 and T3 thyroid hormones that are explicitly labeled gluten-free by the manufacturers. Again, confirming the absence of gluten in any particular product with your pharmacist is recommended.

Natural Desiccated Thyroid Gluten-Free Options

For those wishing to take FDA-approved natural thyroid medications, these are leading brands of porcine thyroid extracts considered free of gluten:

Brand Name Manufacturer
Armour Thyroid Forest Pharmaceuticals
Nature-Throid RLC Labs
Westhroid RLC Labs
WP Thyroid RLC Labs

These products contain both T4 and T3 derived from porcine thyroid glands, plus fillers like lactose and sucrose. RLC Labs explicitly states their products have no gluten-containing excipients. Forest Pharmaceuticals indicates Armour Thyroid is gluten-free. However, those highly sensitive should use caution and consult their pharmacist.

Other Gluten-Free Thyroid Medications

In addition to synthetic hormones and natural thyroid extracts, other hypo and hyperthyroidism drugs that are generally considered gluten-free include:

  • Methimazole – Available as a gluten-free liquid solution (Tapazole)
  • Propylthiouracil – Some tablets confirmed gluten-free by pharmacokinetic testing
  • Potassium iodide – Gluten-free formulations available, contains no excipients
  • Beta-blockers like propranolol – Used for hyperthyroidism, typically gluten-free
  • Radioactive iodine – Used for hyperthyroidism and thyroid cancer, contains no gluten

As with any medication, working with your doctor and pharmacist is important to determine the best thyroid disease treatment options for you, based on efficacy, cost, and gluten-free status. Liquid, powder, or intravenous forms can help minimize gluten exposure.

What About Thyroid Supplements?

There are various over-the-counter thyroid support supplements marketed for hypothyroidism symptoms. These contain vitamins, minerals, herbs, and animal-derived ingredients intended to improve thyroid functioning. Common components include:

  • Iodine
  • Tyrosine
  • Selenium
  • Zinc
  • Copper
  • Ashwagandha
  • Bladderwrack seaweed extract

Since these thyroid supplements are not regulated by the FDA, their gluten content is not rigorously confirmed. The different botanical ingredients, fillers and excipients may pose a risk for gluten exposure. Those with celiac disease or NCGS should scrutinize product labels carefully for any mention of gluten-based substances, or contact the manufacturer to verify gluten testing.

Conclusion

The most frequently prescribed thyroid medications – synthetic levothyroxine, liothyronine and natural thyroid hormones – are widely available in gluten-free forms. Leading brand name versions like Synthroid, Cytomel and Armour Thyroid are confirmed gluten-free by the manufacturers. However, checking with your pharmacist about each drug formulation’s excipients is important to avoid potential gluten exposure, especially from generic thyroid medications. Methimazole, PTU and some supplements may contain gluten. With hypervigilance about ingredients, people with celiac disease and gluten sensitivity can find thyroid treatment options that meet their medical needs and avoid symptoms.

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