Tails of Seattle: A pets blog
Veterinary Q&A: Thyroid epidemic in dogs?
Posted by Neena Pellegrini
Dr. W. Jean Dodds is a world renown vaccine research scientist and founder of Hemopet, a nonprofit animal blood bank in Southern California. Her latest book is
"The Canine Thyroid Epidemic: Answers You Need to Know for Your Dog," written with Diana R. Laverdure (Dogwise Publishing, 175pp., $19.95). She answers this week's questions about canine thyroid disease.
Question: What role does thyroid play in a dog's health and function?
Answer: In all mammals, the major "master glands" that basically control all body functions are the pituitary gland in the head and thyroid gland in the neck.
The pituitary gland "tells' the thyroid gland what to do, based on the blood levels of free thyroid hormones that circulate through it. When these levels are low, the pituitary gland releases a hormone called thyroid stimulating hormone (TSH), which causes the thyroid gland to increase its output of thyroid hormones.
By contrast, when the circulating levels of thyroid hormones are high, the pituitary gland releases less TSH to reduce further output of thyroid hormones.
Question: Why is it so important?
Answer: Because thyroid hormones, released from thyroid glands, control all the organ and cellular functions of the body.
Question: You say there is an epidemic in canine thyroid disease. Please explain how you reached this conclusion.
Answer: Decades of line breeding and inbreeding within purebred dog breeds -- and even the crossbreeds and mixed breeds -- were designed to "fix" the physical appearance, behavioral and performance traits of particular breed types to standardize the breeds and make them more alike genetically. However, this also placed them at an increased risk of being affected by undesirable health or behavioral conditions.
When we add the increasing effect of pollution of our environment, depletion of the ozone layer in the atmosphere, accumulation of toxic wastes and appearance of more infectious agents, parasites and chemicals to this genetically similar and thus susceptible population of dogs (or other animal species and humans), the increase in autoimmune conditions, including endocrine disorders, becomes inevitable.
Thyroid disease is one of the most vulnerable of these conditions.
Question: Why is the epidemic such a serious issue?
Answer: Because thyroid dysfunction directly affects the health and longevity of the body.
About every aspect of a dog's health is impacted, from maintaining healthy skin and coat to fighting infections to promoting mental alertness and concentration, maintainting the body's temperature and proper body weight.
Question: Why is it such a misunderstood disease?
Answer: Because thyroid disease is a multi-factorial condition that mimics many other syndromes or clinical signs, and it isn't until at least 70 percent of the thyroid gland has been progressively damaged that classical clinical signs of hypothyroidism (underactive thyroid) occur.
So, in early thyroid disease, the diagnosis can be easily overlooked.
Dogs are now contracting thyroid disease at a dramatically younger age. Just 15 years ago, veterinarins generally agreed that dogs younger than 5 to 7 years old were unlikely to have hypothyroidism. Today, dogs ranging from as young as puberty and up to 2 1/2 years old are regularly diagnosed.
Question: Is this a breed-specific disease?
Answer: Not really, although there are at least 20 or more breeds at higher risk. Although the list of the top 25 breeds most affected is continually changing, it is generally composed of the following (listed alphabetically): Alaskan Klee Kai; Beagle; Borzoi; Boxer; Chesapeake Bay retriever; Cocker spaniel; Dalmatian; Doberman pincher; English setter (by far the highest); Eurasier; German wire-haired pointer; Giant Schnauzer; Golden retriever; Great Dane; Havanese; Irish setter; Kuvasz; Labrador retriever; Leonberger; Maltese; Nova Scotia Duck Tolling retriever; Old English sheepdog; Rhodesian ridgeback; Shetland sheepdog; and Staffordshire terrier.
Question: How do genetics factor in?
Answer: Autoimmune thyroiditis is an heritable trait in dogs akin to Hashimoto's thyroiditis in people. All autoimmune diseases in humans and animals have a genetic component associated with genes of the major histocompatibility complex (MHC).
The heritability of thyroiditis in dogs is still being studied by Dr. Lorna Kennedy of the United Kingdom and ourselves. There are two existing publications about this ongoing research project, which now involves 14 dog breeds.
Question: How big are the studies?
Answer: 156 Dobermans in the 2005 paper, and 525 total of 42 breeds in the 2006 study, plus a total cumulative data base of 873 controls of 70 breeds.
Question: What role can age play in thyroid disease?
Answer: Thyroiditis usually doesn't show up until after puberty, which is typically around 9-12 months of age in most breeds.
Question: What role can stress play?
Answer: Stress (emotional, physical, physiological) can precipitate the clinical appearance of a subclinical or latent disease.
Question: Can diet be an issue?
Answer: Yes, especially if diet is imbalanced.
Question: What foods are recommended to maintain thyroid health?
Answer: Just a well-balanced, nutritionally sound diet without excessive iodine or cruciferous vegetables, such as those in the cabbage family, and other "goitrogens," such as soy isoflavones, that can suppress the function of the thyroid gland.
Question: You've linked behavioral issues with thyroid disease. Please explain.
Answer: The connection between thyroid function and behavior has been know in humans since the 1930s. Animals are no different. The brain needs normal amounts of thyroid hormonal activity to sustain its normal functions.
Children and dogs with attention deficit hyperactivity disorder or dogs with unprovoked aggression, submissiveness, adult onset seizures, phobias or compulsive disorders often have thyroid-function defects.
Our studies have shown this relationship to be present in up to two-thirds of behaviorally dysfunctional dogs.
Question: You've listed the top 10 signs of hypothyroidism as: weight change (despite no change in diet); hair and skin changes; fatigue; depression and anxiety; gastrointestinal (bowl) problems; menstrual irregularities and fertility problems; neck discomfort or enlargement; muscle and joint pain; and cholesterol issues.
That's a long and varied list that could be attributed to any number of diseases, excluding hypothyroidism. Why should a pet owner think any of it is linked to thyroid disease? If a dog develops gas or starts limping, thyroid disease isn't going to be high on the list of worries.
Answer: Yes, but recurring gas problems could be early signs of inflammatory bowel disease, which can be due to early stage thyroid dysfunction, and even limping can be a sign of the metabolic imbalance of thyroid function on bones and joints.
So, basically, the point is that pet owners should understand that imbalance of any metabolic function can be from undeelying developing thyroid dysfunction.
Question: How can a pet owner winnow this down to determine if thyroid really is the issue?
Answer: A thorough physical examination, with complete thyroid antibody profiling, a complete blood count, serum chemistry and urinalysis should be performed up front when assessing these cases, rather than a "hit or miss" diagnostic workup.
It's much better to "rule in " or "rule out" this diagnosis at the outset.
Other than proper (complete) diagnostic testing of thyroid function on initial workup of an illness, there is no reliable 'rule out.' This problem with failure to 'rule in or out' an underlying thyroid issue has cost pets countless suffering and their guardians countless dollars - which is a main reason for our book. Awareness is key!
Question: How is hypothyroidism diagnosed?
Answer: With a complete thyroid antibody profile, and not just a total t4 or a T4v , free T4 and TSH. 4.
The vast majority of vets think that testing of serum T4, which measures the total amount of thyroxine hormone in the blood, alone is adequate as the first screening for a thyroid problem and that only if T4 is abnormal should more tests should be done.
This misconception is a huge obstacle to accurately diagnosing canine thyroid disorders. If the T4 is low, you will not know whether the values are accurate without performing additional tests. If it's normal, you may miss the diagnosis altogether, because there could be an antibody preventing you from ever seeing it.
Question: Michigan State University's Diagnostic Center for Population and Animal Health Laboratory is best know for it endocrinology testing and has been the lab of choice for many vets who test for thyroid problems. How does your approach differ from MSU's?
Answer: Many years ago, Dr. Ray Nachriener at MSU and I commiserated about the huge void in complete thyroid profiling and agreed that this had to change. So, while their testing has since become a huge enterprise and considered to be the "gold standard," our smaller, focused thyroid diagnostic program has run for decades in parallel.
What differs at Hemopet is now two-fold: We have been the only vet diagnostic lab that has always applied age-, breed- and activity-specific interpretive comments with our thyroid profiles -- based on a 20-year cumulative data base; and since 2009, we offer patented unique assay technology that does not use radioisotopes (non-RIA) . Our assays are thus environmentally "green."
Question: To the critics who say your patented testing gives you a vested interest in testing for the disease, how do you respond?
Answer: That's just silly. Patents don't earn anyone any dollars; they're only a deterrent to keep commercial companies from infringing on the technology. It's only if patented technology is licensed to some entity and a licensing fee is paid, that money is earned. Even if that were to happen in our case, Hemopet is a nonprofit charity so no one stands to gain personally.
Question: How is hypothyroidism treated?
Answer: With thyroid hormone (levo-thyroxine) given at the appropriate dose for breed, age and optimal weight twice daily - at least an hour before or three hours after foods or treats containing calcium or soy, to ensure absorption.
Question: Are there any side effects to the medication?
Answer: Thyroxine is very safe as a medication. If doses are 10 times higher than required (by gross overdosing or accidental ingestion of many tablets), side effects are typically those of a "revved up" metabolism -- restlessness, panting and pacing, excessive thirst. But, as the half-life of thyroxine in dogs is only 12-16 hours, the overdose effects rapidly dissipate over the next 24 hours. If you suspect that your dog has been overdosed somewhat, then just cut the dose in half for the next several days and see if these signs disappear.
If they do resolve, your veterinarian will need to retest the dog's thyroid levels at four to six hours after the pill was given, and adjust the dose accordingly.
Question: You are known worldwide for your work with vaccines and blood disorders. How/why did you make the leap to thyroid disease?
Answer: Because, it became obvious to me about 15 years ago that I had to look at the whole body and its relationship to all of its parts - i.e. I embraced "wholism", rather than just hematology and immunology.
Dr. W. Jean Dodds is a world renown vaccine research scientist and practicing vet in Southern California, where she founded Hemopet in 1986. Hemopet is a nonprofit animal blood bank, greyhound rescue and adoption program and a diagnostic specialty laboratory. Dodds has been a member of many national and international committees on hematology, animal models of human disease, veterinary medicine and laboratory animal science. In 1974, she was selected Outstanding Woman Veterinarian of the Year by the AVMA. In 1994, she was given the Holistic Veterinarian of the Year Award by the American Holistic Veterinary Medical Association. She has more than 150 research publications.
Read our past Q&As:
Veterinary Q&A: How to find a good vet
Veterinary Q&A: Neutering your dog Part 2
Veterinary Q&A: Neutering your dog Part 1
Veterinary Q&A: Hyperthyroidism in cats
Veterinary Q&A: Incontinence in dogs
Veterinary Q&A: Hanging tongue syndrome
Veterinary Q&A: Bad breath in dogs
Veterinary Q&A: How much is too much exercise for my dog? Part 2
Veterinary Q&A: How much exercise does my dog need? Part I
Veterinary Q&A: A killer called bloat
Veterinary Q&A: Initial care for new puppies
Veterinary Q&A: Knee problems in dogs
Veterinary Q&A: Flea-control treatment
Veterinary Q&A: Bearded dragon lizards
Veterinary Q&A: Vaccinations for indoor cats
Veterinary Q&A: Lumps and bumps
Veterinary Q&A: More on aging dogs and arthritis
Veterinary Q&A: Aging dogs and arthritis
Veterinary Q&A: Puppy and geriatric exams
Veterinary QA: What dogs can safely chew
Veterinary QA: Why does it cost so much to clean a dog's teeth?
Veterinary QA follow-up: More on cleaning a dog's teeth
Veterinary QA: When to spay or neuter
Do you have a question about pet health? Ask now! We'll pose some of your questions to a local vet in an upcoming post.
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