Updated December 16, 2014.
Gary Weitzman, DVM, is one of the best-known veterinarians in the country. He is a licensed veterinarian and an accomplished animal welfare professional with more than 20 years of experience. Dr. Gary Weitzman also has a popular public radio program, "The Animal House," which is a weekly discussion that explores the latest in animal science, pet behavior, and wildlife conservation. Dr. Weitzman graciously agreed to share some information about thyroid disease in dogs and cats in this Q & A.

Question: Are certain breeds of dog or cat more susceptible to thyroid disease?

Dr. Weitzman: We see it in every breed. In terms of dogs, we do see more Golden Retrievers, Labradors, Dobermans, and Cocker Spaniels presenting with thyroid disease more than other dog breeds. Probably the poster boy for thyroid disease is the Golden. About 99 percent of the cats we treat here are domestic shorthair, but every feline or canine breed is susceptible to thyroid disease -- it doesn't discriminate by breed.

Question: Let's say someone just adopted a Golden, or a Golden mix. What's the best way to be proactive about potential thyroid disease, to catch and treat it early? How often should the dog see a vet?

Dr. Weitzman: Healthy dogs should see a vet at least once a year for an annual exam. Looking for signs of disease is the best way to be on the lookout for thyroid disease-weight gain, lethargy, and skin rashes are cardinal signs of hypothyroidism.

Question: Do dogs and cats experience thyroid disease differently?

Dr. Weitzman: Yes -- it's almost uniformly hypothyroidism for dogs, and hyperthyroidism for cats.

Question: Interesting! Starting with dogs, what are the signs and symptoms, and how does canine hypothyroidism resemble its human equivalent?

Dr. Weitzman: Hashimoto's thyroiditis, or autoimmune thyroiditis, is probably the closest equivalent in dogs. It has effects that can be debilitating for dogs. Low thyroid in dogs can lead to classic symptoms of weight gain, lethargy, depression, skin problems (rashes and infections), and hypotension (low blood pressure). Then there are some very bad effects of hypothyroidism; in Dobermans, for instance, it can lead to blood disorders. Another problem, which is more uncommon, that can come from hypothyroidism, is megaesophagus, a disease where the esophageal muscles deteriorate, leading to huge swallowing problems and, eventually, death.

Question: How is the diagnosis made?

Dr. Weitzman: In 90 percent of dogs with hypothyroidism, the symptoms are weight gain, skin problems, and lethargy -- but that can also describe 50 percent of healthy dogs. So the real test of thyroid disorder is a combination of blood tests and the clinical picture. The way we diagnose it is to treat it and, if there's a huge change in the way the dog looks and acts, then we have a diagnosis.

Question: What's the treatment?

Dr. Weitzman: For a lethargic dog with skin problems and an equivocal blood test, we prescribe the same thyroid supplement that many humans take: levothyroxine, or Soloxine. It's widely available at drugstores.

Question: At what age are thyroid disorders usually detected?

Dr. Weitzman: It can happen at any age. We usually don't see it in puppies, but young adults are commonly diagnosed. Around five years of age is the most common time we pick it up. Many dogs are never even really diagnosed -- as many as a quarter to a third of them, in fact. They'll have symptoms, but it's nothing too alarming, so people don't have the tests done, or they don't bring the problem to the vet's attention in the first place.

Question: Have you noticed an increase in pets presenting with thyroid disorder?

Dr. Weitzman: Not really. But again, many are going undiagnosed. Most of the time medicine evolves, so you can get a better diagnosis. But with thyroid disease, it's gotten worse because we have a lot of trouble diagnosing it. We can do T4, T3, free T4... they can be quite labor intensive to do, and often, no single test will give definite answers.

Question: What about cats?

Dr. Weitzman: With cats, take everything we just discussed for dogs and turn it upside down. For starters, hyperthyroidism in cats is usually caused by a benign tumor, not an autoimmune disease. The symptoms in cats are weight loss, hyperactivity, vomiting, and diarrhea. Hyperthyroidism can also cause cats to exhibit behavior changes. One of the things cats do -- to people but not to each other -- is vocalize, and thyroid disease can cause more vocalization. So if your cat is "talking" more than usual, it's time for a thyroid test. Cats can also develop heart problems like hypertrophic cardiomyopathy (HCM), which is the most common cardiac disease in cats. It's wonderful when we can actually stop it because they happen to present with hyperthyroidism -- treat the thyroid disorder, and the heart condition clears up.

Question: What are the feline treatment options?

Dr. Weitzman: We used to have to remove the thyroid gland (thyroidectomy), which is obviously invasive; it's not done very much any more, and shouldn't be, because there are much better ways to treat. In the past, we also put hyperthyroid cats on Tapazole -- the generic name is methimazole -- once or twice a day for life. The bad thing about methimazole is that it can cause vomiting, one of the classic signs of hyperthyroid disorder. So we were continuing that problem with the drug.

The best treatment of all, the gold standard, is radioactive iodine, I-131. It scares people, but it's one tiny injection in the skin and the thyroid disease is cured. The cat does have to be kept in the hospital for a week, because he or she will be slightly radioactive for few days post-treatment.

For people who decide against I-131, Hill's Pet Nutrition has developed a whole line of prescription diets called Y/D. It's a very controlled- iodine cat food that actually in itself can treat feline hyperthyroidism in many cases. To be able to modulate a disease with diet is kind of our whole goal as veterinarians, and Hill is doing groundbreaking work on that.

Question: It sounds as if there are way more feline treatment options than canine ones?

Dr. Weitzman: Nothing has evolved for dogs; the treatment -- thyroid supplement, which is the same used to treat humans with the disease -- has not changed in about 50 years.

Question: For pets that don't have thyroid disorder -- yet -- is there anything owners should be mindful of in terms of prevention and detection?

Dr. Weitzman: Animal health is really, really dependent on the human or humans involved: knowing your animal and watching his behavior and weight, and being really attuned to your animal's health. In terms of diet, I say let's not let hypothyroid dogs gain any more weight; it's good to watch their caloric intake. But remember, hypothyroidism is an autoimmune disease.

Question: It's encouraging to hear doctors like yourself giving thyroid disorder the respect and attention it deserves -- MDs aren't always so compassionate or thorough.

Dr. Weitzman: Actually, we've been ruling out and treating thyroid disease in animals for decades. It has evolved significantly, but it's always been a well-respected, absolutely valid disorder in dogs and cats. And it's taken very seriously because, if undiagnosed and untreated, it can be absolutely devastating in cats, and can make a dog's life miserable. As vets, we love our patients -- I don't know how MDs feel about theirs all the time!

More About Dr. Gary Weitzman

Gary Weitzman, DVM, MPH, CAWA holds a Bachelor of Arts degree in Biology and English from Colby College, a Masters in Public Health degree in International Health from Boston University's School of Public Health, and a Doctor of Veterinary Medicine from Tufts University School of Veterinary Medicine.

Dr. Weitzman joined the San Diego Humane Society and SPCA in May 2012. Serving as a community advocate is very important to Dr. Weitzman and he is committed to collaborating with individuals, rescue groups and organizations to identify innovative solutions to do more for animals and their people. A significant focus for Dr. Weitzman and the San Diego Humane Society is a movement called "Getting to Zero" and it involves a comprehensive plan to save the life of every healthy and treatable animal in San Diego Animal Welfare Coalition shelters.

Prior to his current role at the San Diego Humane Society, Dr. Weitzman was the president and CEO of The Washington Animal Rescue League (WARL), where he led a large, urban, homeless animal rehabilitation and adoption center through a period of unprecedented growth. During his tenure at WARL, Dr. Weitzman was instrumental in guiding the organization into becoming a national resource for disaster and puppy mill rescues and a major resource for other animal shelters nationwide.

In addition to co-hosting "The Animal House," he has published one book for children published by National Geographic, called "Everything Dogs," and another book titled "How to Speak Dog" will be released in fall of 2013.

For more information on Dr. Weitzman's "The Animal House" radio show, or to listen to past shows, visit their website. Pet questions for The Animal House can be submitted by email to animalhouse@wamu.org or via the listener phone-in number 877-610-3647.

Author and pet health advocate Julia Szabo contributed to this Q & A.

_{Source: Interview with Dr. Gary Weitzman, June 2013.}