Kodak, a young bearded collie, was a regular at the park. He loved to play with children and other dogs. Then something odd happened. This outgoing dog became withdrawn and began hiding under the park bench. He refused to play. Worried, his human mom took him to the veterinarian, who could find nothing wrong and suggested that Kodak was simply “bored”.
Kodak’s mom wasn’t convinced. Determined to find answers, she took him to three different veterinary specialists, none of whom could find anything wrong. Friends suggested Kodak might have a thyroid disorder and referred her to veterinarian Dr. Jean Dodds.
“We confirmed that Kodak suffered from hypothyroidism, and we recommended that he immediately begin thyroid hormone replacement therapy to manage his condition,” Dr. Dodds says. Kodak regained his normal energy and behavior almost immediately, and has remained well ever since.
Canine thyroid disorder has reached epidemic proportions. Since many veterinarians do not understand how to properly diagnose and treat it, a lot of dogs are suffering needlessly from a variety of physical and behavioral symptoms. Often, they’re surrendered to shelters – and even euthanized – due to abnormal behavior. Sadly, many of these falsely labeled “bad dogs” suffer from a simple medical condition that could be easily treated.
What is the thyroid gland and why is it important?
The thyroid gland is part of the endocrine system, a collection of glands that produces all the body’s hormones. The thyroid gland is located in the upper third of the neck. It is shaped roughly like a butterfly and is about the size of a Lima bean (this varies depending on the size of the dog). The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), hormones that control virtually every metabolic and cellular function, including body temperature, resting metabolic rate, heart and respiratory rate, and organ and tissue functions.
What is canine thyroid disorder?
About 90% of the time, thyroid disorder in dogs manifests as hypothyroidism (low thyroid function) as opposed to hyperthyroidism (overactive thyroid). Hypothyroidism occurs when the thyroid gland becomes diseased or destroyed and cannot secret enough thyroxine (T4). Symptoms of hypothyroidism can also occur when the liver does not properly convert T4 into T3, creating a hormone deficiency in the tissues.
Causes of hypothyroidism
About 80% of canine hypothyroidism cases result from an inherited condition known as autoimmune (lymphocytic) thyroiditis, in which the body’s disease-fighting T-lymphocytes are genetically programmed to destroy the thyroid gland. This mechanism of autoimmunity is called the “failure of self-tolerance.” A strong immune system is vital to a dog’s health. Genetic factors, breeding practices, and environmental stressors all tax our dogs’ immune systems, leaving them susceptible to a variety of conditions ranging from autoimmune diseases to cancers.
“Since the 1800s, people have been inbreeding and linebreeding dogs for certain physical and behavioral attributes,” says Dr. Dodds. “At the same time, this selective breeding may also pass along a variety of undesirable inherited conditions, including autoimmune thyroiditis. This makes it even more important to accurately diagnose canine hypothyroidism in its early stages, so that afflicted dogs can be removed from the breeding pool and neutered.”
While some breeds have lower instances of canine thyroid disorder than others, no breed is immune. Even mixed breeds are in jeopardy, since most are a combination of two or three inbred or line-bred breeds that are independently at risk.
Environmental influences, including household chemicals and pesticides, over-vaccination, chemical flea, tick and heartworm preventives, prescription and non-prescription medications, and poor nutrition further stress a dog’s immune system.
Symptoms to look for
Since thyroid function affects just about every aspect of a dog’s health (see sidebar on next page), clinical symptoms can mimic those of other disorders and illnesses. “All too often, this throws veterinarians ‘off the trail’, causing them to overlook or miss the correct diagnosis,” Dr. Dodds says. “People who understand the symptoms of canine hypothyroidism will be empowered to speak out as their dog’s advocate, rather than just automatically following the diagnosis – or even misdiagnosis – of their veterinarian.”
The most classic signs associated with canine hypothyroidism – significant weight gain, lethargy, cold intolerance, and poor skin and hair coat – typically occur only after 70% or more of the thyroid tissue has been destroyed or damaged. Other changes, such as lack of focus, aggression, passivity and phobias, subtle weight gain and food hypersensitivity or intolerance, can present themselves during the earlier phases of the disease.
Diagnosis must be thorough
“Effectively treating canine thyroid disorder begins with proper diagnosis,” says Dr. Dodds. “This is where many veterinarians miss the mark, often only testing T4 (thyroxine) blood levels, which alone are unreliable indicators of thyroid function.”
According to Dr. Dodds, a complete baseline thyroid profile should minimally include:
•Total T4
•Total T4
•Free T4
•Free T3
•Tg AA (thyroglobin autoantibody)
“Dog guardians must insist on a full thyroid panel – and accurate interpretation by a skilled professional – before ruling out a diagnosis of hypothyroidism,” Dr. Dodds advises.
Conventional treatment
Canine thyroid disorder can be easily managed with thyroxine hormone replacement, which is given twice daily apart from meals (since some foods such as soy and calcium bind thyroxine and impair its absorption). Dosage is based on the dog’s age, optimal weight and lifestyle. Continuing this therapy for the rest of the dog’s life is critical; hypothyroidism is easily managed, but never truly cured.
Alternatives to thyroxine
If you’re looking for a more holistic solution, you can substitute natural thyroid extracts made from bovine or porcine thyroid glands. Some of these products contain both T4 and T3 thyroid hormones, so the dosage needs to be adjusted with this in mind. Also, since dosages of natural thyroid extracts are measured in grains (1 grain = 60 mg), they need to be adjusted to match the equivalent synthetic thyroxine dosage. Dessicated thyroid extracts cost more, since relatively large amounts must be given to equate to the higher therapeutic needs of dogs, but they’re a good alternative for those who want a more holistic approach.
As an adjunct to thyroid replacement therapy, whether synthetic or natural, you can also use supplements that help thyroid gland function. The most commonly used are products made by Standard Process, including Thytrophin PMG and Thyroid Support. Although they usually cannot replace the need for thyroid hormone replacement in true cases of hypothyroidism, they can lower the dose of thyroxine or natural thyroid extract needed.
A hypothyroid dog can live a long, healthy happy life if his condition is properly treated. If you feel your own companion might have a thyroid disorder, insist on proper testing by an experienced lab. He’ll thank you for it!
Symptoms of hypothyroidism
Metabolic changes: lethargy, weight gain, mental dullness, cold intolerance, exercise intolerance, mood swings, chronic infections, seizures
Neuromuscular (nerve/muscle) problems: weakness, stiffness, facial paralysis, head tilt, incontinence, drooping eyelids
Skin diseases: dry, scaly skin and dandruff, chronic offensive skin odor, hyperpigmentation, “rat tail”, “puppy coat”, pyoderma Reproductive disorders: infertility, absence of heat cycles, silent heats, testicular atrophy Cardiac abnormalities: slow heart rate, cardiac arrhythmia, cardiomyopathy
Gastrointestinal and liver problems: constipation, diarrhea, vomiting Blood disorders: bleeding, anemia, bone marrow failure Eye conditions: corneal lipid deposits, corneal ulceration, “dry eye”
Behavioral disorders: fear, aggression, anxiety
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