Health · Nutrition · Pet Food · Pet Food Label · Science · Veterinary Care

Give Up the Gullet

I have written about this health issue before; in fact, more than five years ago in the essay “Got Gullet?. Sadly, here we are again, looking at beef gullets and thyroid glands.

A Bit of Review

The thyroid gland is a small organ found on each side of an animal’s trachea. When a cow is dissected for the production of human-grade meat, the trachea and esophagus are removed and become by-products. Although these body parts cannot be sold as foods for human consumption, they can and are used in pet foods and as treats.

Why is this a problem? This can be a problem if thyroid gland tissue remains when these body parts are turned into pet food. Thyroid tissue contains thyroxine (thyroid hormone), which is not destroyed by either heat treatment or by a dog’s gastric acid or digestive enzymes. If included in a food, thyroid hormone will be absorbed into the body and remains active. If a dog consumes enough thyroxine, he or she will develop hyperthyroidism (or more technically correct, thyrotoxicosis). Some dogs develop elevated serum thyroxine but do not show clinical signs. Others develop signs that include weight loss, hyperactivity, excessive panting, and polydipsia/polyuria (increased drinking/urinating).

My earlier Science Dog essay examined a series of cases of thyrotoxicosis in dogs beginning more than 10 years ago. Since that article was published, there have been two pet food recalls for the presence of thyroid hormone in pet foods; one in 2017 and one in 2018. In both recalls, affected dogs became clinically ill and their veterinarians alerted the FDA to the problem. Obviously, those recalls were not enough to effect change. In June of 2021, a group of researchers, some who work for the FDA and others from academia, published a retrospective study of pet food-induced thyrotoxicsosis in 17 dogs.

2017 Recall

In early 2017, The FDA’s Center for Veterinary Medicine (CVM) responded to reports of three dogs, all living in different homes, that developed elevated serum thyroid hormone levels plus clinical signs of hyperthyroidism. All three dogs were being fed either Blue Buffalo Wilderness Rocky Mountain Recipe or Wellness Beef Topper. Both are canned products. The owners were advised by their veterinarians to discontinue feeding the foods. Clinical signs disappeared and serum thyroid hormone levels returned to normal in all three dogs within a few weeks.

In response to veterinarians’ concerns, the FDA tested the identified foods for the presence of thyroid hormone. Both products were contaminated with active thyroid hormone. The source was presumed to be beef gullets that contained thyroid gland tissue. When alerted to the FDA’s findings, both Blue Buffalo and WellPet initiated voluntary recalls of the affected products.

2018 Recall

One year later, four more dogs were diagnosed with diet-induced hyperthyroidism. The contaminated products included several varieties of Milo’s Kitchen treats, produced by JM Schmucker. Removing the treats from the dogs’ diets resulted in resolution of hyperthyroidism symptoms in all of the cases. FDA testing found the presence of thyroid hormone, presumed (again) to come from beef gullets.

What is that definition again?

Apparently multiple cases of dogs diagnosed with thyrotoxicosis plus the recall of multiple brands of foods and treats was not enough to effect change. The pet food industry continues to include the occasional thyroid gland in foods and treats.

2021 Paper

The newest publication details the development of hyperthyroidism in 17 dogs fed commercially prepared dog foods and treats (1). The study focuses specifically on the forms of thyroid hormone and level of contamination in identified pet products and on ingredient sources.

  • Both T4 (the form of thyroid hormone found circulating in blood) and T3 (the most active form of thyroid hormone) were found in the foods and treats (as well as in the serum of the dogs that consumed the foods). Jerky treats were more likely to have elevated T4 concentrations while contaminated canned products had elevated T3.
  • Because of T4 and T3 differences among products (and in the blood of ill dogs), the authors recommend that veterinarians who suspect diet-induced thyrotoxicosis should conduct a full thyroid test panel. Typically, not all veterinarians test for both T4 and T3 and their various forms, which could result in a missed diagnosis.
  • Measurement of iodine (a component of thyroid hormone) in foods may provide pet food manufacturers with a method to screen for the presence of thyroid gland tissue in their products.
  • The researchers conclude that according to the FDA’s current draft guidelines for good manufacturing practices: “Thyroid gland from the use of gullet is discussed in draft GFI # 245 as a known or reasonable foreseeable hazard.


In 2015, I wrote this: “At the very least, this set of case studies provides sufficient evidence that diet-induced hyperthyroidism is a health risk that warrants further study and investigation of the identified companies and brands“. Yet, today, despite knowing that dogs also are at risk of developing hyperthyroidism if they consume thyroid gland-containing foods, despite documented cases of dietary thyrotoxicosis, and despite multiple recalls, there is still no specific regulation that bans the inclusion of thyroid gland tissue in pet foods or pet treats.

Enough is enough. Further research is NOT needed. Rather, what we DO need is a ban on the inclusion of livestock animal thyroid glands in pet foods and treats. These are a known and demonstrated health risk to dogs.

What can an owner do?

Well, first, do not feed gullet treats. Second, since the industry apparently is not capable of preventing this contamination, avoid foods that are high in beef products. If you do wish to feed beef-based foods, your best bet is to select a product that uses only human grade ingredients, since thyroid gland is prohibited from foods meant for human consumption. Last, if you are concerned, and you feed a food that you like and your dog does well with, contact the manufacturer and ask how they ensure that their foods are not contaminated with beef gullets containing thyroid glands.

It really is time to give up the gullet.

Cited Study:

  1. Rostein D, Jones JL, Buchweitz J, et al. Pet food-associated dietary exogenous thyrotoxicosis: Retrospective study (2016-2018) and clinical considerations. Topics in Companion Animal Medicine 2021; 43:1-7,

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3 thoughts on “Give Up the Gullet

  1. I understand the recommendation to give up gullets (surrounded by the thyroid gland in many vertebrates), but not the recommendation to avoid beef-based foods in particular. The thyroid gland is a synapomprphy (shared derived trait) of most vertebrates. Lambs have a thyroid gland. Chickens have a thyroid gland. So do fish, and in many fish the thyroid cells are diffusely scattered in the body and so perhaps more likely to wind up in fish-based pet food.


  2. I have wondered whether this might be linked to Feline Hyperthyroidism. I can now test cat or dog food for thyroid hormone; if anyone is interested, please feel free to contact me.


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