On Monday, March 27, 2017, the U.S. Food and Drug Administration(FDA) issued an alert advising pet owners and caretakers, veterinarians, and the pet food industry that pet food and treats made with livestock gullets (meat from the throat region) have the potential to contain thyroid tissue and hormones. Pets that eat food or treats containing thyroid hormones may develop hyperthyroidism, a disease that is rare in dogs and in spontaneous cases is usually triggered by thyroid cancer.

This alert was issued after a recent investigation into reports of three dogs in different households that showed signs of hyperthyroidism. That investigation led to the voluntary recalls of two pet food products.

The MSU Diagnostic Center for Population and Animal Health can provide all of the tests FDA has shown to be altered in this incident, endocrinology interpretations, and phone consultations.

We encourage our clients to read the FDA's letter to veterinarians related to Exogenous Hyperthyroidism and Thyroid Hormones in Pet Foods. This letter contains case information, results of dog testing and food testing, instructions for reporting suspected cases of exogenous hyperthyroidism, and additional background on thyroid gland in pet foods.

Tests run on the dogs included a full thyroid panel for T3, free T3, T4, free T4, TSH, thyroid autoantibodies, and iodine. The FDA has published the results but not the specific values and ranges due to variations between laboratories. However, the following overall patterns were seen:

• Active (T3) and inactive forms (T4) of thyroid hormones
  • HIGH total T3
  • LOW total T4
• Protein bound and unbound forms (free T3, free T4) of thyroid hormones
  
  • HIGH free T3
  • LOW free T4
• Thyroid stimulating hormone (TSH)
  • low NORMAL TSH
• Autoantibodies (T3, T4, thyroglobulin)
  • NORMAL autoantibodies (T3, T4, and thyroglobulin)
• Total iodine
  • elevated total iodine

This pattern of results led the consulting veterinarian at the FDA reference laboratory to suspect an exogenous source of thyroid hormones, ultimately resulting in identification of the contaminated food products.