Animal & Veterinary

Thyroid Hormones in Pet Food - Pet Food Industry

March 27, 2017

Dear Members of the Pet Food Industry,

The FDA’s Center for Veterinary Medicine has recently investigated a cluster of three dogs of various ages, in separate households, that exhibited symptoms of hyperthyroidism. Hyperthyroidism in dogs is unusual, and can be life threatening if not treated.

In these cases, extensive testing at a reference laboratory was performed on all three dogs in the cluster. This testing showed elevated thyroid hormone in the blood, but the full thyroid panel results ruled out thyroid cancer and were most consistent with an external hormone source. Information from the dogs’ owners revealed that all three dogs had been fed specific products from two brands of canned dog food.

Based on the recommendation of the reference lab’s consulting veterinarians, the feeding of these dog foods was discontinued. Once the dogs stopped eating these products for a few weeks, their clinical signs disappeared and thyroid hormone levels returned to normal. An FDA lab tested unopened cans of the two products and confirmed that they contained active thyroid hormone. The source of thyroid hormones is likely the use of gullets from which the thyroid glands were not completely removed before adding to pet food or treats.

After consultation with FDA, the two companies initiated voluntary recalls of the implicated lots of the food products. The company-issued press releases, including recalled product information are available here and here.

The FDA appreciates the cooperation and swift action taken by both companies to address this issue.

For detailed veterinary testing information related to this cluster, please see our Dear Veterinarian letter.

The Problem

Pet food and treats in all forms (dry food, canned food, treats, etc.) with elevated thyroid hormone levels likely contains animal gullets (laryngeal tissue) in which the thyroid glands were not completely removed.

USDA prohibits the use of thyroid glands and laryngeal muscle tissue for human food.

Any products containing livestock gullet or laryngeal tissue is a potential source of thyroid hormones.1

If a thyroid gland is not completely removed from a gullet and that gullet is then added to pet food or treats, remnant thyroid tissue could be a source of thyroid hormones.

One way to be certain that there are no traces of thyroid in pet food is to avoid the use of livestock gullets.

Questions & Answers

How could thyroid glands end up in pet food?

The most likely scenario is that the thyroid glands have not been completely removed from animal gullets and then those gullets are used in pet food or treats.

How can I make sure that there are no thyroid glands in my product?

Suppliers can ensure that they have fully removed thyroid glands from gullets before providing them to manufacturers. The FDA recommends consulting industry trade organizations, such as the Pet Food Institute or the Association of American Feed Control Officials (AAFCO) for best practices and advice.

Manufacturers can carefully assess their suppliers’ practices and take steps to ensure that they are receiving raw materials and ingredients that do not contain thyroid hormone secreting tissue.

What should I do if I think there may be thyroid glands in my product?

If you suspect that there is a problem with your product or supply, the best course of action is to assess your products and practices, consulting the FDA as needed.

Members of industry with specific questions about products and practices can contact the FDA’s Center for Veterinary Medicine Office of Surveillance and Compliance by emailing AskOSC@fda.hhs.gov.


1Broome, MR, 2015. Exogenous thyrotoxicosis in dogs attributable to consumption of all-meat commercial dog food or treats containing excessive thyroid hormone: 14 cases (2008-2013). disclaimer icon J Am Vet Med Assoc 246: 105-111.

Page Last Updated: 03/27/2017
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