| | Published July 17th, 2013
| Canine Hypothyroid Disease
| | By Mona S. Miller, DVM |  | |
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Is Fido tired all the time? Does his fur look patchy and dry, or he has ongoing skin infections? Is he 2-8 years old? Have you tried to get him to lose weight, but no matter what you do, he is still fat? Is he a golden retriever? Hypothyroidism is the most common hormonal disorder in dogs. Some breeds are predisposed, although this can occur in any dog. It is fairly common in golden retrievers, dachshunds and Dobermans. I have many patients who are hypothyroid who feel and look better within a month after starting treatment. I specifically talk about this condition with my clients who own goldens, Labradors and other medium or large breed dogs who come to me frustrated about their unsuccessful attempts to get their dog to lose weight.
The thyroid glands near the throat are responsible for making the active hormones that regulate metabolism throughout the body. Thus, low levels of thyroid hormone can affect almost every organ system. The most common causes of thyroid deficiencies in dogs are by natural decrease or atrophy of the glands, or by immune-mediated destruction of the glands. Less common causes are from iodine deficiency in the diet or a congenital disorder.
This can be a relatively easy disease to diagnose with blood tests. In simple cases, the screening T4 hormone is low, there is a mild anemia and a mild to moderate high cholesterol level. As an aside, this is an important area in which dogs differ from humans. Dogs are not subject to the same process of atherosclerosis, or cholesterol deposition in blood vessels, as humans. Cholesterol levels in dogs are not nearly as meaningful as it is in humans, but in the case of hypothyroidism, high cholesterol can serve as a marker. Veterinarians generally do not separate out HDL and LDL cholesterols.
However, in some cases, diagnosis is not so straightforward. When a dog is ill, for almost any reason, his thyroid level may be low during the illness. This is called Euthyroid Sick Syndrome. Medications such as anti-seizure drugs, anti-inflammatory drugs, and certain antibiotics can cause a decreased level of circulating T4. Some breeds, such as Greyhounds and other sight hounds, usually have much lower T4 levels as their norm. More specific and sensitive thyroid testing can be done to differentiate whether true hypothyroidism exists. It may also be appropriate to use thyroid medication as a trial in order to make the diagnosis.
Treatment is relatively easy, straightforward and lifelong. Thyroid supplement is given in the form of a pill. This is another important difference between dogs and humans - dogs usually require supplement twice daily and at much higher doses than humans. Initially the dose should be checked with a blood test, and each time the dose is changed, checked again. For dogs that remain at a stable dose, it is reasonable to check their blood T4 level every 6-12 months. Most veterinarians prefer to check the peak level during the day, which should occur about 4-6 hours after the morning pill. In some cases, though, a trough (or low) level would be recommended, so your vet would ask you to bring Fido in just before his next dose is due.
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 | | Dr. Mona Miller lives in Lafayette with her son, two cats and Luka, a yellow Labrador. She has worked in the Lamorinda area since moving here in 2001. She attended U.C. Berkeley as an undergraduate, and received her DVM from U.C. Davis. She can be reach via email at MonaSDVM@aol.com.
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Lamorinda Weekly, Moraga CA