November 2016 | TheDogPress SideEffectsStella Starr, Pet Perspectives
How much do you remember about what the thyroid gland does for the metabolism of meat eaters? Did you know thyroid hormone regulates the immune system? Okay, then you know thyroid balance affects your overall health and that of your carnivorous pets.Dogs and cats can suffer from dietary low thyroid hormone. The thyroid gland controls just about every other hormone. If the thyroid gland or the immune system breaks down, it can bring on disease of the liver, heart, pancreas, and the largest "gland" of all, the skin. That's where you see dull dead hair, a sure sign of thyroid hormone deficiency in people and animals.Last week a cat show judge-friend spent the night at my house. She commented that my old girl’s coat looked dry and lifeless. I catalog my favorite books (since before internet) and it didn’t take us long to find that way back in 1984 Drs. Mark E. Peterson and Duncan C. Ferguson authored a comprehensive chapter on thyroid diseases in the textbook of Veterinary Internal Medicine, third edition. They described the canine thyroid as relatively inefficient in retention of iodine. That’s when I decided to warn you dog people.I had been using a new brand of cat food and checking the label, we realized that the “fish picture” on the label was misleading, it had no fish or source of iodine! Fish may not be as important to dogs but if you own a "northern breed" you should note that those Arctic breeds evolved on a high fish diet which provided good usable iodine required by the canine thyroid gland. Take away the fish and you may find, even generations later, that your Malamute, Akita, or Siberian’s thyroid goes "off". Cats love fish so much that pet food makers usually include enough fish to keep the feline thyroid gland working but as they say, times change.
The textbook book dealt more with dogs than cats. We laughed and decided that realistically, back in the 80s most cats came and went as they pleased and ate whatever they caught outside. But I decided that dog people would find this interesting…Lymphocytic Thyroiditis and Idiopathic Atrophy are the two most common forms of hypothyroidism in adult dogs. Knowing that would be of interest to TheDogPress.com readers, I dug into it. Lymphocytic thyroiditis is thought to be an immune-mediated disease caused by a build-up of antibodies which attack the dog's own tissues or glands. I took that to imply over-vaccination, poor diet, or medication could have that effect but I looked up “idiopathic.” It is defined as "an independent disease neither relating to or dependent on any other existing condition." In other words, veterinarians aren't sure what causes it. Congenital (at birth) and secondary hypothyroidism (caused by tumors or other abnormalities) are just a tiny percentage of canine thyroid problems.Today's vet may dismiss your dog's "thyroid problem" as genetic if for no other reason that along with all the science they get in vet school, young students also assimilate the attitude that breeders cause all health problems. That is not you or you wouldn't be reading this. Jean Dodds, a hero DVM to most of us, stated there can be a genetic predisposition because given similar external factors, some animals (and humans) become symptomatic while others do not. Who would argue that. The book said that thyroid imbalance can be caused by stress, diet, environment, radiation, chemicals, antibiotics, and toxins. I know a few dog breeders and keep in touch with my cat friends but I wonder how many know that? We are still told that thyroid problems are “hereditary” and given pills to “correct” it, right?It makes sense that breeding colonies with the same food and environment, the incidence of thyroid and/or immune system problems may seem more prevalent in some family groups. But that probably has nothing to do with the genes. It is more frequently the diet but how many vets dig into what you feed before they decide it is the bloodline? Believe me it happens in cats too!Instant Information why hypothyroidism is rare in herbivores but carnivores on pet foods with the ingredient ii bromine frequently suffer thyroid hormone imbalance.Low thyroid hormone can cause weight gain and other health problemsI will try to sum up what I gleaned from the textbook. Thyroid hormone acts as an immune system stimulant by causing the pituitary to release growth hormone. The hypothalamus in the brain measures the amount of thyroid hormone in the blood. When thyroid hormone levels are too low, the hypothalamus sends a message to the pituitary gland which results in a release of TSH (thyroid stimulating hormone) so it is easy to see that the balance between the immune system, thyroid gland, and the pituitary (master) gland is critical. Somewhere in TheDogPlace.org I read about the pituitary gland, sunlight, and house pets.According to R.W. Nelson, DVM and S.L. Ihle, DVM, Purdue University School of Veterinary Medicine, "hypothyroidism is a common endocrinopathy facing today's small animal clinician." Okay, so why is it COMMON? It can be hereditary in the sense that it can be a congenital defect but I struggled through and sure enough, it is more often caused by an external influence such as medications, chemical exposure and most common of all, poor diet, especially as to what is genetically appropriate to particular species or breed.When a bloodline begins to produce unusual genetic defects, it's easy to say, "it must be something in the water." We can't overlook contamination such as Love Canal and nuclear plant tragedies such as occurred in Japan but most researchers attribute immune system problems to the immediate environment, food, stress, or prescription medication. Antibiotics such as Tribrissen, Septra, Bactrim, and Diatrim can affect the thyroid as can drugs such as the Nitrofurans, Butazolidin, Phenobarbital, and heartworm preventatives.Diagnosis of thyroid disease is more reliable today. If you, as a savvy breeder, "sense" something is off, insist your dog or cat be tested.Diagnosis of thyroid disease is more reliable today. If you, as a savvy breeder, "sense" something is off, insist your dog or cat be tested. The average veterinarian today treats pet animals, not breeding stock. He or she will look at an animal with decent hair coat and no visible skin lesions and say, "looks okay to me". Should you protest that your dog is gaining weight even though she is on a strict diet or that he or she has missed several matings, some vets will secretly thinks that's a good thing.Nowadays, too many veterinarians think "breeders are bad, purebreds are inbred, pet overpopulation problem" so you may have to insist on a blood test because you know your dog better than anyone. If you suspect a problem, do not be put off by your vet's reluctance to perform thyroid testing which will require him to become conversant on a subject in which he has no knowledge or interest!Adding to the diagnostic complexities, thyroid levels can fluctuate depending on something as seemingly unrelated as a fence fight, a weekend of shows, or estrus. If test results are normal but borderline, a recheck in two weeks could result in a completely different reading. My judge-friend pointed out that a dog with seemingly normal blood levels may still have a hormone deficiency if the thyroid receptors are low, insensitive, defective, or blocked. Lab tests may disagree with symptoms because a quantity of thyroid hormone is measured rather than its biological effectiveness for that animal.A conscientious vet will take test results, symptoms, and clinical condition of the dog under consideration before making a diagnosis. I hope this thyroid information has helped you and that your breeder's brain will have instant recall if you experience any of the following: irregular seasons, infertility, unexplained weight gain, cold intolerance, personality changes ranging from mental dullness to lethargy to aggression, dull coat, greasy or flakey skinIf your dog shows any of these symptoms, suspect thyroid hormone deficiency and get your dog tested! If test results indicate thyroid hormone supplementation is in order, before you do anything else, think about "why?" Most veterinarians would agree that once you put your dog on synthetic hormone, he/she is probably on the prescription for life.