The Fan Hitch Volume 2, Number 2, February 2000

Newsletter of the Inuit Sled Dog

Table of Contents

The Bigger Picture
Featured Inuit Dog Owner: 
Paul Landry
Book Reviews:
On Thin Ice
Of Dogs and Men
Poem: Brave Little Heart
Janice Howls: 
Hypothyroid Disease
Fan Hitch Contributor Receives Writing Award
Expedition News: 
The Thule 2000
In My Humble Opinion: 
Traditional Advice
The Nunavut Quest 2000
Ihe ISDVMA Meeting

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Index of articles by subject

Index of back issues by volume number

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Ordering Ken MacRury's Thesis

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The Fan Hitch Website and Publications of the Inuit Sled Dog– the quarterly Journal (retired in 2018) and PostScript – are dedicated to the aboriginal landrace traditional Inuit Sled Dog as well as related Inuit culture and traditions. 

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Janice Howls........Hypothyroid Disease

by Janice Dougherty

Much has been written about hypothyroidism in the canine press over the past decade, and with good reason. It is all too common in dogs, and is especially common in breeds that are/were large and active; but in fact it is rare in toy and miniature breeds. Unfortunately, it is not something that is apparent at birth or in early puppyhood where it could be more efficiently removed from the breeding population. The breeds reported to be pre-disposed to hypothyroidism, according to Merck, are the Golden Retriever, Doberman Pinscher, Irish Setter, Miniature Schnauzer, Dachshund, Cocker Spaniel and Airedale Terrier. But closer to our concerns, it has been noted by Miki and Julie Collins in "Dog Driver" to be all too common in the better known sled dog breeds such as the Alaskan Malamute, Samoyed and Siberian Husky. It is also well known among more distant relatives like the Akita and Chow Chow. Dr. Arleigh Reynolds of Cornell University, a competitive driver of Alaskan Huskies, once suggested that it was widespread among some Alaskan Husky kennels, when he stated that many of those dogs are routinely medicated with synthetic thyroid hormone. This observation has been recently echoed by Dr. Mark May, another musher veterinarian in the January/February 2000 edition of Mushing in an article by Will Forsberg entitled "Educating Mushers". Please understand that while supplemental thyroid hormone may correct an imbalance in a dog at rest, or for companion animal type activities, it cannot hope to fully return the gland to its correct, healthy ability to respond to stress or athletic performance of the magnitude of an expedition or race. Perhaps some of the unexplained deaths of dogs during races is linked with this disease. The thyroid gland has been referred to as a master gland, especially by Dr. Jean Dodds whose research and writings should be accessed for more specific, technical information. The thyroid is the metronome, the "idle screw" of the body. It controls the basal metabolic rate, regulating the body's response to all changes/challenges. It makes glucose (sugar energy) available to meet metabolic demands by increasing the breakdown of glycogen stored in the muscles, and the use of stored fats for the same purpose. It increases glucose absorption in the intestines, stimulates new protein synthesis (makes muscle, antibodies and performs tissue repairs), stimulates heart rate, cardiac output and blood flow, increases neural transmission, cerebration (thinking) and neuronal development in young animals. In fact, an article in last August's New England Journal of Medicine discussed the impact of maternal hypothyroidism and fetal development. It seems that thyroid deficiency during the latter two thirds of gestation and the first months after delivery can result in mental retardation and sometimes neurologic deficits. The article went on to suggest routine screening for subclinical (not obvious) hypothyroidism be added to all pregnant women's care. The clinical signs associated with hypothyroidism vary from dog to dog, and not every sign will present in every affected dog. Some of the classic signs are: (1) a gain in body weight without an associated change in appetite (2) decreased activity, reluctance to play, mental dullness, producing either a lumpy or sometimes an aggressive, cranky dog (3) shivering, heat seeking, inability to maintain normal body temperature (4) changes in skin and hair coat: skin thickens, increased skin folds around the face creating a sad, tragic expression; tail may become almost bare, skin is scaly, symmetrical alopecia (baldness), lack of coat regrowth, persistent infections (5) mild, non-regenerative anemia (6) muscle tone is lost, muscles are soft and doughy (7) lack of libido, reduction in sperm count, abnormal/absent estrous cycles with reduced conception rate (8) impaired joint function. I won't go into the details of the impact of this disease on each of the organ systems, but suffice it to say that the picture is not one of a vigorous athletic animal. It is the antithesis of what an Inuit Sled Dog or any useful creature needs to be. I recall an argument some years ago that a low thyroid was a sign of an efficient use of energy, and therefore correct in a breed that was an "easy keeper". I never could keep a straight face when I heard that one. A high functioning thyroid does not mean "hyperthyroidism". It does not mean crazy, obsessive-compulsive, burn out. A high functioning thyroid is ready to respond in a split second to the needs of the animal/person by fine tuning the metabolism to maintain homeostasis or balance and continued harmony. It speeds up the immune system when faced with a challenge, it heals wounds, it neutralizes and removes waste material. It helps use fuel for warmth and work and repair, or keeps the animal's cooling system working when needed. 

Why should I be writing about this for the Fan Hitch? Although hypothyroidism may not now be a genetic problem in the ISD, it has the potential to develop here as it has in so many other breeds. It has already been noted in the New Guinea Singing Dog, which is about as primitive a breed as they come, if only in Southern Hemisphere, dingo style. If we would be smug and secure, we must remain vigilant. Hypothyroidism is suspected to be polygenetic in its inheritance. From a practical point of view, that means that the multiple genes that produce it may accumulate until there are enough of them to be expressed clinically in symptoms or diagnosed in blood tests, but as their frequency increases, more and more individual dogs will reach "threshold" and express the disease. Low thyroid levels may begin to show up at 6 months of age in some dogs. It has been suggested that dogs kept for breeding be tested at puberty, when thyroid activity is normally very high (younger, rapidly growing dogs have a greater uptake of iodine and a faster rate of release) and that part of our selective process include a consideration of the results of such a test. Normal values in lab work were originally estimated by averaging the values of a population of dogs ASSUMED to be normal. We need to know what is normal for an ISD, not for a 13 year old mastiff who is assumed to be normal. I have personally known of dogs who had all the "earmarks" of hypothyroidism, but the vet used by the owner told them that the dog was just "low normal". Six months to a year later, they became clinically diagnosed.  There are marked differences in thyroid morphology (shape and structural proportions) and function between canine breeds of European origin and the Basenji (another primitive), which originated in Africa. At the same level of iodine intake, thyroidal turnover of iodine in the Basenji is 2 to 3 times faster than in European breeds. People who own and love Basenjis will tell you that they are more active than most people want, and that some owners have put runway shelves on the walls of their dogs' enclosures, since they like to climb and bounce off the walls. Beyond those Inuit people who have returned to their traditional lifestyle, no one is going to stress test their dogs sufficiently to eliminate the early hints of any weakness, including hypothyroidism. In the book "Dog Driver" it was suggested that people had inadvertently selected for dogs with subclinical hypothyroidism because they were softer and easier to handle, having what was considered "a better temperament". [I have also heard about an article that was published as part of the proceedings of the International Council of Archaeozoology, held in Victoria, B.C. that would link hypothyroidism to domestication. If any readers can direct me to the original text, I would be grateful.] 

So, here we are, trying to preserve a piece of the Pleistocene as far as our dogs go. Although modern society fantasizes about Jurassic Park and raising the Mammoth from the ice and inseminating an elephant egg with its DNA, I am sure that most of them would dirty their diapers if they had to live with an ISD. When normal, active children and normal, active pets are being medicated into submission, what better than to breed for the ideal dog which doesn't bark, doesn't bite, doesn't challenge the most sniveling, inept owner. Is it any wonder why large active breeds of dog are the ones most commonly affected by hypothyroidism? And why dog breeds small enough to be dismissed as amusing, even at the height of their ferocious displays, are not affected? A fully affected dog is a medical concern, but a subclinically affected dog, one who has just the beginnings of this dumbing down disease, is the one who is most likely to be successfully placed as a pet - and reproduce his kind. 

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