Hypothyroidism in dogs

You may have noticed your dog is putting on a few pounds lately although you haven’t changed its diet. After taking your pet to your veterinarian, it has been discovered that your pet has an under active thyroid gland. Just what is hypothyroidism?

Hypothyroidism is a disorder in which the thyroid gland (two small lobes located in the neck ) secretes insufficient thyroid hormone. Hypothyroidism isn’t life threatening, but it does diminish quality of life. Once diagnosed, however, the disorder is relatively easy to treat.

The thyroid gland produces the thyroid hormones that are critical to maintaining your dog’s normal metabolic rate. This is the speed at which the body converts nutrient energy into energy fueling the body. If the thyroid gland degenerates or becomes inflamed, it can no longer produce sufficient quantities of hormones. As a result, cells don’t convert the nutritional energy it needs into biologically usable fuel as fast as usual.

This decreased cell function causes a number of physical changes in a hypothyroid dog. Nearly half of such dogs gain weight (with no change in diet). Over a third become lethargic and mentally dull, and just under a third show hair or skin abnormalities. Hair-producing cells slow down, so there is less hair growth and more hair loss. Skin-producing cells slow down, so there is more wrinkling and seborrhea (dandruff) . Also, hypothyroid pets may suffer an increased propensity to joint disease, especially ligament damage.

Some veterinarians also suspect a link between behavior problems and hypothyroidism. Increased aggression is the most commonly suspected behavior change, but some veterinarians speculate that a few hypothyroid dogs may develop anxiety- related or compulsive behaviors. If your pet develops a sudden behavioral change, have your dogs thyroid status examined.

Since the physical signs of hypothyroidism develop gradually and vary from dog to dog, the disorder often goes undiagnosed. But veterinarians have found that hypothyroidism typically develops after 2 years of age and is more common in certain breeds such as golden retrievers and Doberman pinschers. While all owners should be on the lookout for changes in their dog’s appearance or behavior that suggest hypothyroidism, owners of middle-aged dogs or genetically predisposed dogs should be especially watchful. If you notice any signs, consult your veterinarian. By simply taking a sample of your dog’s blood, it can be determined if the dog has hypothyroidism. At Columbia Veterinary Associates, we are recommending testing as part of our senior health examinations.

Diagnosing hypothyroidism would seem to be as simple as measuring thyroid-hormone levels in the blood. However, this simple technique can give an inaccurate diagnosis because some illness such as Cushings disease- overactive adrenal glands– and medications, such as cortisone suppress the level of circulating thyroid hormones. The most accurate test is the – thyroid stimulating hormone -TSH- response test. In this test, the veterinarian measures thyroid-hormone levels in the dog’s blood, administers TSH (a chemical that stimulates thyroid-hormone secretion), then remeasures hormone levels to determine whether the thyroid gland responded by producing additional thyroid hormones. While the TSH response test is reasonably accurate, it is expensive to administer. Also, this hormone is now difficult to find because of decreased production by the manufacturers.

Newer tests are available, that are as accurate (although not 100 percent) and less expensive than the TSH response test. With these tests the a combination of the levels of thyroid hormone -T4- and a specific thyroid hormone-Free T4 – as well as the level of TSH in a dog’s blood are measured. Hypothyroid dogs have both a high TSH level and a low free-T4 level.

Veterinarians treat hypothyroidism by prescribing supplemental thyroid hormone, which the owner must administer to the dog orally once or twice a day. These medications are initially prescribed according to your pet’s weight. Your veterinarian will closely monitor your dog in the initial stage of treatment by retesting the thyroid level- T4- to make sure the animal is getting the appropriate dosage. Too little hormone won’t alleviate the signs, while too much can cause a dog to develop hyperthyroidism (excessive thyroid hormone causing agitated and overactive behavior, weight loss, excessive drinking, and excessive urination). Once thyroid- hormone levels have stabilized within a normal range, your veterinarian will likely check the levels every six months to every year. The dose levels of medication used to treat this disease in dogs is much higher than the rate use to treat hypothyroidism in people.

Once treatment begins, most hypothyroid dogs are increasingly active and show fewer behavior problems within a week. Hair growth typically accelerates in about a week, too, although bare spots may take months to fully grow in. Most dogs begin to lose excess weight within 2 to 4 weeks of starting treatment.

If you suspect hypothyroidism, consult your veterinarian. The treatment for hypothyroidism is straightforward, and the medication is relatively inexpensive.


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