Hypothyroidism, A Commonly Misdiagnosed Canine Disease

Not all dog diseases are easy to diagnose. The following are examples of commonly misdiagnosed dog diseases:

• Hypothyroid disease
• Addison’s disease (hypoadrenocorticism)
• Cushing’s disease (hyperadrenocorticism)
• Ehrlichosis infection
• Laryngeal Paralysis
• Lyme infection (Borreliosis)
• Myasthenia Gravis
• Portosystemic Shunt

A previous Caring for Pets discussion described why Addison’s disease and Cushing’s disease are easily misdiagnosed. Here, let’s discuss hypothyroidism, which is the disease I see most commonly misdiagnosed.

Symptoms of hypothyroidism, the chubby dog

The most common finding in hypothyroid dogs is obesity. These dogs gain weight even on very little food, which is gloriously perplexing for the families who swear they feed only the tiniest amount of kibble. Occasionally, there will be dogs, especially those on well balanced raw and home-cooked diets, that are hypothyroid but are not chubby, but usually hypothyroid dogs are chubby.

Common symptoms of hypothyroidism include:

·          obesity

·          dry skin and frequent skin infections

·          hair loss (alopecia)

·          slow heart rate (bradycardia)

·          weakness and lethargy

·          coldness or heat-seeking behavior

·          muscle and nerve problems, including facial nerve paralysis

·          dry eye (keratoconjunctivitis sicca or KCS)

·          megaesophagus

·          laryngeal paralysis

·          misbehaviour or aggression

How is hypothyroidism diagnosed?

“Hypo” means low and hypothyroidism is diagnosed with thyroid-specific blood tests that show low thyroid hormone. Typically, hypothyroid dogs have low T3 (tri-iodothyronine) and low T4 (tetra-iodothyronine) with increased TSH (thyroid stimulating hormone).

Early in the disease, some dogs also have antibodies to the thyroid gland (autoantibodies) but as the disease progresses, the antibodies destroy the thyroid cells, thyroid antibodies are no longer produced and tests for autoantibodies are negative.

In addition to thyroid specific blood tests, other blood tests are often abnormal in the hypothyroid dog. For example, hypothyroid dogs often have:           

·          low red blood cells (anemia)

·          low albumen

·          increased cholesterol

·          increased liver enzyme alkaline phosphatase (ALP)

·          increased creatine kinase from muscle wasting.

While many hypothyroid dogs have one or more abnormal blood values mentioned above, some dogs will have disease without significant changes in their blood. The best way of diagnosing hypothyroidism in these dogs is to treat them for the disease and see if their symptoms improve.

What goes wrong in the hypothyroid dog?

Hypothyroidism occurs when the thyroid gland quits producing hormones T3 and T4. Thyroid hormones circulate through the blood and alter the DNA in cell nuclei throughout the brain and body. Thyroid hormones upregulate the DNA responsible for stimulatinh cell growth and metabolism. These genes ensure that cells are metabolizing energy at the proper rate, just as a carburetor ensures a car consumes fuel at a proper rate.

Without the proper levels of T3 and T4, dogs become lethargic. They gain weight. Their skin become dry, their hair thins, then falls out creating bald patches.

In addition to being physically sluggish, many hypothyroid dogs become intellectually sluggish. Some families misinterpret physical and intellectual sluggishness as normal ageing. It is not.

Low thyroid hormone levels also change the brain and behaviour, specifically increasing misbehaviour and aggression. In fact, aggression and behaviour changes are so common in the hypothyroid dog that the number one test recommended for a dog that is misbehaving is a thyroid blood test.

Why is hypothyroidism frequently misdiagnosed?

What I see happening is that blood tests show dogs in low normal thyroxin range when the dogs are already clinically hypothyroid. For example, if the range of thyroid hormone is 8-53 and the dog’s thyroxin measures 10, most vets will say the dog is within the normal range. While some of these dogs will be normal, others will have symptoms of thyroid disease and they should be given thyroid hormone supplements.

Treating hypothyroidism

Here is where there’s great news: hypothyroidism is easy to treat. Dogs are given thyroid replacement hormone medication (levothyroxine sodium) twice a day (BID), with the normal range being 18-22 mcg (0.018-0.022 mg) per kg body weight BID. Meds are started at ¼ to 1/3 of the normal dose for the weight of the dog and increased over a month long period to the normal dose. For example, a 10 kg dog would work up to a full dose of 0.2 mg BID over a month’s time.

Adjusting the medication dosage

While the hormone is being increased, we watch for panting, restlessness, increased heart rate or increased respiration, and difficulty sleeping—all signs of too much thyroid hormone or hyperthyroidism. If we see signs like these, we don’t increase to the full thyroxin range and may back off the dose.

After three weeks on the normal or healthy dose for the dog, a thyroid blood test is done to ensure the hormone levels are in the normal range.

Although medicating for hypothyroidism is easy, the blood test to ensure thyroid hormone levels are normal is a little difficult. The blood must be taken 4-6 hours after the morning med, when we expect the thyroid hormone to be at a peak level. It is ok if this medicated peak is higher than the normal thyroxin peak. For example, if the normal thyroxin range is 8-53, it is ok for the medicated dog to have a level 5-8% higher than normal as the dog is acting normally and has no symptoms of hyperthyroidism.

Nutritional changes to help hypothyroid dogs

Since food in the brassica family binds iodine and decreases thyroid hormone (contain goitrogens), stop frequent feeding of broccoli, cabbage, cauliflower, kohlrabi, Brussels sprouts, rutabaga, turnips. Do feed occasional sea weed and ocean fish because they provide iodine.

Herbs to help hypothyroid dogs

Several Traditional Chinese Medicine (TCM) herbal formulas can help hypothyroid dogs, and the correct formula is chosen based on all the dog’s symptoms. These herbs can be given along with conventional medication, including levothyroxin:

·          Ba Wei Di Huang Wan (Rehmannia Eight)

·          Bu Zhong Yi Qi Wan (Arouse Vigor or Ginseng & Astragalus)

·          Xiao Yao San (Rambling Ease, Free and Easy Wanderer or Bupleurum and Tan Kuei)

Ba Wei Di Huang Wan (Rehmannia Eight) for hypothyroid dogs

Rehmannia Eight is ideal for the hypothyroid dog that is chilly and needs to sleep under the covers, has arthritis, weak or cold legs, neurasthenia, degenerative myelopathy, or kidney failure. Rehmannia Eight helps with all these problems because it treats Kidney Qi deficiency and Kidney Yang deficiency by tonifying and draining damp. Rehmannia Eight is the most commonly prescribed “old dog” formula.

Bu Zhong Yi Qi Wan (Arouse Vigor or Ginseng & Astragalus) for hypothyroid dogs

Arouse Vigor is ideal for the hypothyroid dog that has problems with prolapse, hernia or haemorrhoid. It helps dogs with behaviour problems including anxiety, noise sensitivity, territoriality, separation anxiety, or phobias. Arouse Vigor helps dogs with anemia, including immune mediated haemolytic anemia, and with immune deficiency. As the name suggests, Arouse Vigor also helps dogs with chronic illness, fatigue, weak limbs, and heat-seeking behaviour. Arouse Vigor helps with these problems because it tonifies, moves Qi, and raises sinking Qi, affecting the TCM organs of Spleen, Stomach, Liver. It helps with Liver blood deficiency and Yang deficiency.

Xiao Yao San (Rambling Ease, Free and Easy Wanderer or Bupleurum and Tan Kuei) for hypothyroid dogs

Rambling Ease is ideal for hypothyroid dog that has digestive and liver disease, including anorexia, inflammatory bowel disease, constipation or diarrhea, cirrhosis, microhepatica, ascites, hepatitis or elevated liver enzymes. It also helps with behaviour problems, including depression, irritability, pacing and restlessness, emotional instability, timidity, and anxiety. Rambling Ease helps the hypothyroid dog that has skin disease including allergies, demodex, and pyoderma. Rambling Ease helps with all these problems because it treats TCM diagnosis of Liver Blood deficiency, Liver Qi deficiency, Liver Yin deficiency, Spleen weakness. It is ideal for harmonizing the TCM organs of Liver and Spleen.

Acupuncture to help hypothyroid dogs

Acupuncture points that help hypothyroid dogs include:

·          CV 22

·          GV 3

·          GV 4

·          K 3

·          K 7

·          K 10

·          K 27

·          ST 40

·          BL 23

·          SP 6

·          LV 3

·          GB 34

·          GB 41

Breeds that are genetically predisposed to develop hypothyroidism

There is a genetic tendency to develop hypothyroidism in these dog breeds: Doberman Pinscher, English Setter, Dalmatian, Basenji, Rhodesian Ridgeback, Old English Sheepdog, Boxer, Maltese, Chesapeake Bay Retriever, Beagle, Cocker Spaniel, Shetland Sheepdog, Siberian Husky, Border Collie, Husky, Akita, and Golden Retriever.

Breeds that are not genetically predisposed to develop hypothyroidism

The following breeds have the least likelihood of developing hypothyroidism: Chihuahua, Lhasa Apso, Pomeranian, Miniature Pinscher, Cairn Terrier, Basset Hound, Schnauzer, Miniature Schnauzer, Yorkshire Terrier, Boston Terrier, Norwegian Elkhound, Greyhound, Portuguese Water Dog, Newfoundland, Bichon Frise, Welsh Corgi, Cavalier King Charles Spaniel, and Flat Coated Retriever.

Are spaying and neutering associated with increased likelihood of hypothyroidism?

Yes, spaying and neutering are associated with increased likelihood of hypothyroid disease according to a five-year study at University of Wisconsin Veterinary Medical School published in the American Veterinary Medical Association Journal. The study found that neutered males and spayed females were 3-4 times more likely to develop hypothyroid disease than were intact dogs. If your dog is one of the breeds predisposed to develop hypothyroidism, consider leaving it intact.

Vaccines and hypothyroidism

Many holistic veterinarians believe that unnecessary vaccines predispose dogs to develop hypothyroidism. This occurs because the immune cells become overstimulated by unnecessary vaccines, look for targets, and attack the thyroid gland. Research by Dr Schultz, et al has shown that a single vaccine in a healthy pet at least 4 months of age can protect for life for canine parvovirus, canine distemper virus, as well as for feline parvovirus, feline calicivirus and feline herpes virus. See “Age and long-term protective immunity in dogs and cats” by R D Schultz1; B Thiel; E Mukhtar; P Sharp; L J Larson published in the Journal of Comparative Pathology in January 2010;142S1(0):S102-8.

When it looks like hypothyroidism, but isn’t

Thyroid function is strongly influenced by the dog’s overall health. Some dogs that are ill with diseases other than thyroid disease (infection, cancer, kidney or liver disease) can have low thyroid hormones but actually have a normal thyroid. We call this the sick euthyroid syndrome. Doing full blood and urine tests and a full clinical exam will differentiate sick euthyroid dogs from hypothyroid dogs.

 

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