Hyperthyroidism is uncommon in dogs.1 Most reported cases of canine hyperthyroidism are caused by differentiated, autonomously functional thyroid gland carcinomas.1–5 Although hyperthyroidism is almost exclusively caused by autonomously functioning thyroid adenomas in cats, few cases of hyperthyroidism secondary to functional thyroid gland adenomas have been reported in dogs.6,7
Thyrotoxicosis, regardless of its origin, causes clinical signs in dogs consistent with those reported in other species, including polyuria, polydipsia, and weight loss.1,8,9 Thyrotoxicosis refers to the biochemical and physiologic manifestations of excessive circulating concentrations of thyroid hormone.9 Hyperthyroidism is a term reserved for disorders that result in the overproduction of hormone by a patient's thyroid gland.9 However, thyrotoxicosis is not always attributable to hyperthyroidism.9,10 In people, several terms are used to describe the means by which exogenous thyrotoxicosis resulting from ingestion of excessive amounts of thyroid hormone11 occurs, including thyrotoxicosis factitia,12 surreptitious thyrotoxicosis, occult factitial thyrotoxicosis,13 and thyreoidismus medicamentosus.14 The term thyrotoxicosis factitia veterinarius has been used to identify cases of thyrotoxicosis secondary to the accidental dosing of human patients with veterinary (T4) preparations.15 Excessive thyroid hormone administration in a hypothyroid patient, a form of thyrotoxicosis factitia, is an obvious potential cause for thyrotoxicosis and should be easy to exclude via a thorough anamnesis.1,16
Dietary sources of excessive thyroid hormone may also occur. Numerous reports17–20 of thyrotoxicosis secondary to consumption of ground beef contaminated with thyroid tissue, so-called hamburger thyrotoxicosis, have been reported in the human literature. Thyrotoxicosis in a dog secondary to the consumption of feces from a housemate that was receiving levothyroxine has been reported in the veterinary literature.21 Two recent reports22,23 of thyrotoxicosis in dogs secondary to consumption of diets containing raw meat or dried gullets, presumably contaminated with thyroid tissue, have also been published. To the authors’ knowledge, there are no other published reports of thyrotoxicosis in dogs secondary to consumption of commercially available dog foods or treats. The purpose of the study reported here was to describe the clinical, laboratory, and scintigraphic findings in dogs with exogenous thyrotoxicosis attributable to consumption of commercially available dog foods or treats.
Canine thyroid stimulating hormone
Digital Imaging and Communications in Medicine
OsiriX, Pixmeo, Geneva, Switzerland.
Antech Diagnostics, Irvine, Calif.
IDEXX Laboratories Inc, Westbrook, Me.
Diagnostic Center for Population and Animal Health, Michigan State University, Lansing, Mich.
Organic Chicken and Brown Rice Recipe Sticks, Trader Joe's, Monrovia, Calif.
Liv-A-Littles 100% Beef Protein Treats, Halo Purely for Pets, Tampa, Fla.
Canine R/D Dry Dog Food, Hill's Pet Product Inc, Topeka, Kan.
Pro Treat Raw Natural's Real Beef with Berries and Flaxseed, MiracleCorp, Dayton, Ohio.
Jerky Strips with Real Beef, Hill's Pet Product Inc, Topeka, Kan.
Roll-A-Rounds Chunky Lamb Formula, Natural Balance Pet Foods, Burbank, Calif.
Beef Jerky, Milo's Kitchen, Big Heart Pet Brands, San Francisco, Calif.
Farmers Market Chicken and Vegetables Flavored Dog Treat Strips, Plato, Fresno, Calif.
Chef Michael's Grilled Sirloin Steak Flavor, Nestlé Purina Pet-Care Co, St Louis, Mo.
Science Diet Light Dry Dog Food, Hill's Pet Nutrition Inc, Topeka, Kan.
Catalog No. 19-620C, 2 mL capacity containing 4–2.38 mm stainless steel beads, Omni International, Kennesaw, Ga.
Omni bead ruptor homogenizer, Omni International, Kennesaw, Ga.
Canine T4 Coat-A-Count, Siemens Healthcare Diagnostics, Los Angeles, Calif.
Prism, version 6, GraphPad Software Inc, La Jolla, Calif.
Natural Beef Air Dried Dog Food, The Real Meat Co, Montrose, Calif.
Lamb Jerky Treats, The Real Meat Co, Montrose, Calif.
Natural Beef Jerky Treats, The Real Meat Co, Montrose, Calif.
Thawed Beef Raw Dog Food, Whisker & Paws, Costa Mesa, Calif.
Beef Recipe Jerky Strip, Trader Joe's, Monrovia, Calif.
Pup-Peroni Stick Treats, Big Heart Pet Brands, San Francisco, Calif.
Venison Jerky Treats, The Real Meat Co, Montrose, Calif.
Max Meat Air Dried Dog Food, Only Nature Pet, Boulder, Colo.
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