canine thyroid epidemic

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Many people are aware that hypothyroidism (low thyroid function) is a medical condition that can cause an afflicted dogs to become lethargic, dull, and fat. But far too few pet owners are aware of the behavioral symptoms that hypothyroid can cause. This is unfortunate, since these symptoms include unexplainable aggression, so-called “rage syndrome,” severe phobias, and cognitive disorders. Lacking an explanation for the sudden onset of these serious behaviors, and gaining no improvement through training, many owners tragically opt to euthanize these troubled dogs.

If an afflicted dog is very lucky, however, his owner will ask a veterinarian to order blood tests that can confirm a diagnosis of hypothyroidism; the treatment is simple and not expensive.Dogs who suddenly become aggressive should be tested for low thyroid. Unaware the behavior may be linked to a medical problem, some owners turn to training methods. This may help, but can’t solve the underlying problem. Other owners may give up.  It’s important to ask, however, since not many veterinarians are aware of the prevalence of hypothyroid’s behavioral signs.

RANGE OF BEHAVIOR PROBLEMS

Dr. Dodds and other veterinarians and researchers have been linking changes in behavior to hypothyroidism for more than a dozen years. The various types of abnormal behavior can be grouped into three categories: aggression, extreme shyness, or seizure-like activity.

The cases involving aggression are often similar to Hannibal’s. A previously even-tempered animal lashes out at another animal or human without any warning. One such dog under the care of Dr. Dodds was successfully participating in performance events. One day the dog’s behavior changed radically and he “would go berserk” every time he saw people he didn’t know. Soon he was banned from the training facility because his aggressive behavior had escalated to dangerous levels. Sadly, it’s not unusual for dogs with untreated hypothyroidism to become so aggressive that their owners are no longer able to manage them.

On the other end of the behavioral spectrum are the dogs that become very shy and fearful due to hypothyroidism. While not a threat to humans, extreme manifestations of this kind of behavior still render the dog difficult, if not impossible to keep as a family pet. In addition, these animals are unlikely to be able to continue any activities such as obedience, showing, or working.  The final type of behavioral aberrations seen with hypothyroidism is sudden onset of seizure activity. According to Dr. Dodds, these dogs “appear perfectly healthy outwardly, have normal hair coats and energy, but suddenly have a seizure for no apparent reason.” The seizures may be infrequent, and may include aggressive behavior immediately before or after the seizures.

WHICH DOGS ARE MOST AT RISK?

It used to be that the stereotypical dog with hypothyroidism was middle-aged and a mid- to large-sized breed. Today, says Dr. Dodds, “the majority of dogs diagnosed with hypothyroidism are young adults. They’re one and a half, not four or five like we used to see.”And there no longer seems to be a link between size and thyroid dysfunction. The top 20 most-affected breeds range in size from Rhodesian Ridgebacks to Maltese.

DIAGNOSIS REQUIRES A FULL PANEL

Any time a dog presents with a behavior problem, particularly one of sudden onset, it is recommended that the owner take the dog to a veterinarian for a full physical exam, complete thyroid panel, blood chemistry/CBC, and urinalysis. After all, a dog can have something as simple as a urinary tract infection and be in horrible pain, causing the unusual behavior.  You have to be particular about the thyroid test, however. Insist on having your dog’s blood sent to a reputable laboratory and tested for all the thyroid hormones and autoantibodies to those hormones. In-office thyroid tests, or simple tests of your dog’s “total” T4 levels, are inadequate for diagnosing hypothyroidism.

Research done at Auburn University indicates that in-house T4 tests are unreliable and inaccurate about 52 percent of the time in dogs. “Having treated lots of animals for hypothyroidism, the most important thing I can recommend is the panel versus the total T4. Every time I think that you can tell something from doing just a total T4, I’m mistaken,” says Dr. Pressler.  In addition to the possibility of inaccurate readings, the total T4 can be in the “standard” reference range, but too low for a particular dog’s age, breed, or size. And the other levels found in a full thyroid panel give a much clearer picture about how the thyroid is functioning. A complete thyroid panel tests these six levels, plus TgAA:

• Total levels of thyroid hormones thyroxine (T4) and Triiodothyronine (T3)
• The availability of T4, as indicated by “Free T4” (FT4)
• The availability of T3, as indicated by “Free T3” (FT3)
• The autoantibody levels of T4 (T4AA)
• The autoantibody levels of T3 (T3AA)

• TSH (Thyroid Stimulating Hormone)

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Dr. Dodds says that testing for autoantibodies is particularly important, because elevated levels of autoantibodies indicate thyroiditis, regardless of T4 or T3 levels. “Those animals are having inflammatory immune-mediated lymphocytes attack and damage the thyroid gland,” she explains. It’s important to proactively treat these dogs, she adds, because when you’re dealing with behavior issues, the dog could end up with serious aggression before the total T4 ever tests too low.

Don’t let recent “normal” tests keep you from suspecting thyroid issues, should your dog’s behavior change suddenly. Hannibal had a full blood panel in July, which included T4, which came in at 1.4. At that point, he was acting normally. His behavior started to change subtly until he had the three incidences of aggression, and he was diagnosed as hypothyroid in November.

Results that are in the normal levels as dictated by the lab aren’t necessarily normal for your dog. Dr. Dodds has fine-tuned the optimal levels for different ages and breed types. Generally speaking, younger dogs should have higher thyroid levels (in the top half of the “normal” range). Geriatric and large- or giant-breed dogs have “normal” levels that are closer to the bottom part of the normal range. Sighthounds normally have very low basal thyroid levels.

TREATMENT SUGGESTIONS

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The standard treatment for hypothyroidism is hormone replacement with a synthetic T4 compound, L-thyroxine, often called by the brand name Soloxine. Depending on the dosage, a month’s supply for an average-sized dog costs between $5 and $10. Once diagnosed, Dr. Dodds starts treatment. The standard dose is 0.1 mg per 12-15 lbs of optimum bodyweight twice daily.“The half life is 12-16 hours, so we don’t recommend putting them on once a day ever,” says Dr. Dodds, despite some people’s experience that their dogs do “fine” on once a day dosing, and some medication labels give once per day dosing instructions.

Finally, Dr. Dodds suggests that thyroid medication be given to the dog directly by mouth, rather than in the food bowl. Owners who feed their dogs home-prepared diets are warned not to give the medication within a half-hour of a calcium-rich meal, such as meaty bones or a dairy-rich food, as it will interfere with absorption of the medication.

ADDITIONAL TREATMENTS

In addition to thyroid medication, Dr. Dodds recommends certain supplements and remedies for dogs with hypothyroidism and behavior issues in particular. “We use flower essences to calm agitated dogs. Give them Rescue Remedy before or during high-stress situations,” she suggests.Glandular supplements are an obvious choice for dogs with endocrine dysfunction (see “Grand Glands,” WDJ March 2003). But when you’re dealing with a risky behavior case, medication is the right place to start, says Dr. Dodds. She’s had patients who are reluctant to use any kind of drug.“I can understand where they’re coming from; they want to use glandulars, but they keep shoveling them in and they don’t work. That’s no good, especially if you have a behavior case, where you can’t take a chance.”

WHAT TO EXPECT AFTER TREATMENT

Most of the cases that Dr. Dodds sees have responses like Hannibal’s. “I would say at least 80 percent of the cases have a remarkable improvement; it’s unusual to have them not improve.”  Even more gratifying, the improvement is often quick. Most animals show improvement from two days to two weeks after starting treatment; some may take up to 30 days. Interestingly, a collaborative study between Dr. Dodds and Tufts University has shown many dogs experiencing aggression issues, as a symptom of hypothyroidism, show a favorable response to thyroid replacement therapy within the first week of treatment, even when it took about three weeks to correct the metabolic deficit.

Follow-up blood work should be performed six to eight weeks after medication is started. Blood should be drawn four to six hours after dosing to monitor the dog’s response. Dr. Dodds considers results that are between the upper third of the lab’s “normal” reference range to 25 percent above that to be optimal.  She also recommends a complete thyroid profile at the time of the recheck. “It is essential for animals with autoimmune thyroiditis to determine if the autoantibodies are waning,” she explains.  In most dogs, the autoantibodies begin to decline after treatment starts. This is significant in that it indicates that the autoimmune destruction of the gland is declining or even stopping. But it doesn’t mean the dog is cured. It’s important to maintain the dog’s medication to keep a recurrence of the thyroiditis at bay.

• WHOLE DOG JOURNAL
• DR. JEAN DODDS, DVM
• HYPOTHYROIDISM & CANINE BEHAVIOR
• IS BAD BEHAVIOR CAUSED BY HEALTH PROBLEM? 
• HAPPY HEALTHY DOG