Hypothyroidism (low thyroid) is an endocrine disease seen in middle-aged dogs. Occasionally in certain breeds such as Doberman pinschers or Staffordshire Terriers or mixes of these, it can be seen as young as 1-2 years of age. Some common breeds affected include Golden Retrievers, Labrador Retrievers, herding breeds, Poodles, and mixes.

There are many visible symptoms of low thyroid and they can be very subtle! The most common include weight gain despite no increase in food intake, lethargy, exercise intolerance (can’t walk as far as they used to), dry skin, and “tragic facies” (the dog looks depressed). Because the thyroid controls everything about you-how fast you breathe, your heart rate, ability to fight off infection, etc. other areas of the body may be affected: slow heart rate, respiratory noises (“stridor”), recurrent bacterial skin infections-scaling/dryness, black pigmentation to the skin, weakness of muscles/ligaments, dry eye (KCS), and lack of hair regrowth where shaved, etc. They can each present with only 1 symptom or several. I’ve often said that of 20 hypothyroid dogs, no 2 will look alike!

The diagnosis is made by checking a blood level of thyroid-most often a FT4—this test is more specific than a T4 because there are other diseases and drugs that can artificially lower a T4 level whereas the FT4 test is not affected as much, if at all, by other drugs or diseases. Steroids, sulfa drugs, and nonsteroidal antiarthritis drugs such as Rimadyl can all falsely lower the T4 measurement.

Once the diagnosis is made, thyroid supplement is given-Thyrotabs. It is dosed according to the dog’s weight and given twice daily initially. The dose of thyroid supplementation given to dogs is much higher than what is used in humans. Dogs tend to excrete thyroid in their feces and are very “sloppy” utilizers of thyroid! After 60 days of Thyrotabs, the FT4 level is rechecked after 3-4hrs following the morning pill to be sure the dog is absorbing the dose correctly. Sometimes the dose has to be adjusted and rechecked until adequate absorption is achieved. Most dogs respond in 2 weeks to thyroid supplementation in that they have more energy, etc. but skin changes may take several months. In fact, some dogs will look worse before improving as the thyroid stimulates hair growth and that new growth pushes out all the old skin dryness from the pores.

Hypothyroidism in the dog is easy to treat, it’s the diagnosis that can be elusive as in some dogs, the symptoms are very subtle!

We would be happy to answer/discuss any further questions you may have on canine hypothyroidism!

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