Hypothyroidism is a condition that exists when the thyroid stops producing enough hormone to regulate a normal metabolism. Hypothyroidism often goes undiagnosed for years, but there are signs to look for. If you see these signs in your dog over a period of time, make an appointment with your veterinarian and have your dog tested for hypothyroidism.
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Age
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The most likely age for a dog to develop hypothyroidism is from 4 years of age to 10 years of age.
Breeds
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Hypothyroidism is seldom seen in most miniature and toy breeds, and seems to have the most concentration in mid-size and large-breed dogs. Certain breeds seem to suffer from hypothyroidism more than others. Those breeds are Irish setters, miniature schnauzers, golden retrievers, doberman pinschers, cocker spaniels, dachshunds and Airedale terriers.
Sex
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One sex is not more predisposed to hypothyroidism than the other. However, there are more cases of hypothyroidism in spayed females than in intact females.
Features
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Because the thyroid controls metabolic functions, the symptoms vary among dogs. There is not a single symptom alone that tells a veterinarian that a dog has hypothyroidism, but certain combinations of the symptoms usually cause a veterinarian to suggest thyroid testing.
Identification
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A study on hypothyroidism yielded the following results. In 70 percent of the cases, the dog showed signs of lethargy or mental dullness. Dogs in 65 percent of the cases had hair loss. In 60 percent of the cases, weight gain or obesity was present. Dogs in 60 percent of the cases had issues with dry coat or excess shedding. Twenty-five percent of the dogs had hyperpigmentation of skin. Fifteen percent of the dogs displayed an intolerance to cold. Ten percent of the dogs registered a slow heart rate, while a whopping 80 percent had high blood cholesterol. Fifty percent of the dogs suffered from anemia.
Testing
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Several tests are used to diagnose a dog with hypothyroidism. The Baseline T4 test is a blood test that checks the T4 hormone level in the dog and is usually the first test a veterinarian runs. The Baseline T3 is similar to the T4 test in that it checks for a hormone level in the blood, but the T3 hormone is often stable even when the dog has hypothyroidism. The Free T4 by Equilibrium Dialysis test determines the amount of "free" T4 hormone in the blood. Free hormones are not attached to proteins and can enter cells. If a TSH level test shows elevated TSH levels and the T4 and T3 tests were low, then it is likely the dog has hypothyroidism. In a TSH Simulation Test, the dog is injected with TSH and tested after six hours for an increase in the T4 level. If the T4 level has increased, the dog is not likely to have hypothyroidism.
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