Over the years I have become aware of one of the greatest endocrine disorders in our breed known as Thyroid Disease, specifically Hypothyroidism. Hypothyroidism is a disorder which is not life threatening, but does diminish the quality of life of a dog if not diagnosed and treated. I became aware of this due to finding out the hard way with dealing with it in two of my dogs both emotionally and financially. Thus, it sparked my interest in the disorder/disease and to find out more about it as to what specifically is the function of the thyroid gland and the disorder/disease, genetic disposition, clinical signs, tests, and treatment.

 The Thyroid Gland has a number of functions, I won't however get into the thyroid's physiology, but its function within the body is best well known to regulate the metabolic rate, control the immune system, the hormone system, and the enzyme system of the dog. These four systems are extremely important to a dog’s healthy life. To go further into the depths of this disorder/disease, a pup can be free of all noticeable signs but it is usually apparent by the time the pup reaches the age of 2 years when most of its hormones are or have matured. Unfortunately during that time, if a pup is predisposed to it due to genetics, the disorder/disease has been already working on the pups thyroid gland, and in essence, destroying its vital function and the clinical signs are apparent and treatment must be administered immediately.

The most common cause of canine thyroid disease is autoimmune thyroiditis (estimated 90% of cases). Thyroiditis is an immune-mediated process that develops in genetically susceptible individuals and is characterized by the presence of antithyroid antibodies in the blood or tissues. Thyroiditis is believed to start in most cases around puberty, and gradually progress through mid-life and old age to become clinically expressed hypothyroidism once the thyroid glandular reserve has been depleted. During this process, the animal becomes more susceptible to immune-mediated or other diseases affecting various target tissues and organs. ‘And it should be noted that the prerequisite genetic basis for susceptibility to this disorder has been in established in humans, dogs and several other species.

For a pup to be predisposed to the disorder/disease, it is believed that it has been passed on by its mother through genetics (recessive or polygenetic), or a bitch with antithyroid antibodies in her blood may pass these along to her puppies in her colostral milk. So thyroid screenings is recommended between 10 - 14 months and subsequently every one to two years thereafter.

On another interesting note, fluoride has also been connected with hypothyroidism. I was shocked because most of our dog foods these days contain fluoride and some of our city drinking water does too. A study conducted reported that most of our dog foods contain a "low" fluoride content as 55 or 56 ppm (or mg/kg) and as "high" as 460 ppm (mg/kg). At this high amount that would make it 114 times the maximum contaminant level for fluoride levels in drinking water. Could we be unknowingly contributing to our dog’s hypothyroidism this way?.

The clinical signs associated with Hypothyroidism is lethargic behavior, weight gain, bacterial skin infections, dry flaky skin, hair loss all over the body and/or what is known as the "rat tail" which is hair loss on the trunk of the tail which discolors and thickens where the hair is lost, muscle or nerve weakness, exercise intolerance, hyper excitability, mega esophagus, unprovoked aggression, seizures, cardiac arrhythmia’s, cardiomyopathy (enlarged heart), infertility, lack of libido, decreased or absent sperm count, irregular or absent heat cycles, silent heats, pseudopregnancy, weak, dying, or stillborn pups, vomiting diarrhea, low red and white cell counts, eye problems, loss of smell, chronic active hepatitis, cold intolerance, a slow heart rate, ear infections, and depression. Some of these clinical signs can be singular or compounded as two or more signs together.

 The most common test used for thyroid screening is to check for the T₄ level. This is a measurement of the main thyroid hormone in a blood sample. If it is below normal and the correct clinical signs are present, the test is meaningful. However, testing for the T₄ level can be misleading because some dogs that are not hypothyroid may have subnormal levels. This happens when another disease is present or when certain drugs are given. If hypothyroidism is suspected but the T₄ is normal, other tests can be performed. These are more expensive so they are not used as first line tests.

Treatment of this disorder/disease is quite simple and inexpensive. Once diagnosed by your vet, he or she will prescribe a synthetic thyroid hormone pill to be administered to your dog every day of its life. Hypothyroidism is treatable but not curable. It is treated with oral administration of a thyroid replacement hormone. This drug must be given for the rest of the dog’s life. There is a standard dose that is used initially; it is based on the dog’s weight. However, after about one month of treatment, further testing is done to verify that the thyroid hormone levels are normal. In some dogs, the dose will need to be further adjusted every 6-12 months. Signs of hyperthyroidism can be caused. These include hyperactivity, lack of sleep, weight loss, and an increase in water consumption. If any of these occur, notify your vet so that a proper adjustment can be made.

In conclusion, I would like to say that it is important to our breed to test for this as with hips and heart. We owe it to our dogs and for the longevity of the breed to be responsible owners and breeders. I am not saying that this is something which should or will happen over night as any serious testing for health concerns have only come into the spectrum of our breed in the recent years. So please start checking for thyroid as it is recommended and should be done between 10 - 14 months of age and subsequently every one to two years thereafter, or after clinical signs start to immerge

Respectfully yours and for the love of my dogs,

Jacqueline Linke

Orthopedic Foundation for Animals: www.offa.org

www.AskDrPetra.com

Fluoride and 'Man's Best Friend, Kootenai Valley Times, July 27, 2000,

Weekly Edition, : Dr. Gloria Gilbere