Hypothyroid Conditions in Dogs

• by

  David McCluggage, D.V.M., C.V.A.

Hypothyroidism implies that there are lower than normal levels of thyroid hormone. This condition is most common in dogs. It is also seen in cats (very rarely) and birds (also rare).

Western Medicine and Hypothyroidism

Conventional Western veterinary medicine recognizes that hypothyroidism is a syndrome. Many causes lead to a lack of enough thyroid hormone. Perhaps the most common cause of hypothyroidism is due to the development of a condition called "autoimmune thyroiditis." An autoimmune reaction is triggered for unknown reasons. This leads to inflammation and progressive deterioration of thyroid function.

Potential factors leading to autoimmune thyroiditis:

1. Genetic predisposition
2. Environmental toxins
3. Malnutrition (commercial diets probably play a significant role here)
4. Excessive Vaccinations

Some Signs Common in Hypothyroid Dogs:

1. Lethargic
2. Overweight
3. Hair loss, lack of luster to the coat, color changes to the coat
4. Heat-seeking, lack of tolerance for the cold
5. Behavioral changes, including fear, aggression, apprehension
6. Heat cycle abnormalities
7. Slow heartbeat and decreased metabolic rate
8. Rarely seizures, dementia, and stroke
9. Laryngeal paralysis
10. Neurological diseases (partial paralysis, senility)

Diagnosis of Hypothyroidism

It is quite hard to decide if a dog is hypothyroid. There are many different tests available to the veterinarian; however, their interpretation can be very confusing. Dogs are often misdiagnosed and inappropriately place on thyroid hormone.

The most common test to run is a blood test called "T4". Although inexpensive, this test is too inaccurate to rely on in most cases. In fact, all the tests available are very difficult to interpret. Endocrinologists usually recommend that almost all of the tests be used together. Even when employing all the available tests, the correct diagnosis remains elusive.

Often, the diagnosis rests on the clinical impression, or opinion, of the veterinarian. Many doctors will place suspected hypothyroid dogs on synthetic thyroid hormone (levothyroxine) to evaluate the dog's response to therapy. Synthetic thyroid hormone is a stimulant, so most dogs will look and act more vibrant and alert when placed on thyroid hormone, making many caretakers believe their dog is doing better. Unfortunately, this stimulant effect comes at a severe price for a dog that is not thyroid deficient: as it creates an abnormally high metabolic rate. This effect will burn up the body's vital resources, leading to rapid aging and the development of other disorders, not unlike what happens to a person taking "uppers".

Conventional Western Therapy for Hypothyroidism

Although there are a number of causes and symptoms of dogs with hypothyroidism, the primary method of treating this disorder is to use synthetic thyroid hormone called levothyroxine (some brand names include Soloxine and Synthroid).

Levothyroxine is a very potent drug, and it certainly is needed in many patients. Its benefits and problems include:

1. Powerful enough to have a positive effect on increasing thyroid blood levels in almost all patients.
2. It can be lifesaving in severely hypothyroid dogs.
3. It can partially reverse some of the worst disorders that occur in some hypothyroid dogs.
4. Given twice daily, thyroid blood levels will tend to rise and drop twice daily, meaning the body has highly variable levels of thyroid hormone throughout the day. Naturally, the body's thyroid gland secretes small amounts of hormone which maintains consistent thyroid levels and can increase the amount secreted to meet minute by minute demands required by basic metabolic processes. With supplementation, there can be no consistency of blood levels and, "on-demand" increases. Instead, at times, the body has excessive amounts of the hormone, while at other times, the thyroid levels are too low.
5. The primary role of the thyroid hormone is to regulate the body's metabolic rate, so at times the body is running too fast or hot, and at times it is running too slow or cold.
6. Levothyroxine will produce powerful negative feedback to the thyroid gland, eventually shutting off natural thyroid hormone production completely.
7. This negative feedback tends to atrophy the thyroid gland. Over time, when a dog is placed on levothyroxine (even a dog that has normal thyroid function), the thyroid gland becomes unable to function normally.

Complementary and Alternative Therapies for Hypothyroidism

From the above discussion, one can see that the decision to place a dog on thyroid replacement hormonal therapy should be carefully considered. The thyroid gland is seldom completely inactive in hypothyroid dogs. It is useful to understand that the thyroid gland has a variable and progressive lessening of its ability to produce thyroid hormone. Since most dogs do have a functional thyroid gland, it is a reasonable idea to see what can be done to support normal thyroid function before instituting thyroid hormone replacement therapy. Since the natural thyroid hormone is far better for the body, it is helpful to nurture the thyroid gland, encouraging it to function as normally as possible for as long as possible. Since synthetic thyroid hormone has the opposite result, that being a worsening of normal glandular functions, it is helpful to use therapies that nurture or promote healthy thyroid glandular activity. This encourages the thyroid gland to more closely and accurately produce the exact levels of thyroid hormone needed throughout the day.

In the earlier stages of hypothyroidism, these therapies alone are all that is needed. In more advanced cases, where synthetic thyroid hormone is needed, supplementation with therapies that nurture the thyroid gland will still help your dog regulate its thyroid gland.

For dogs with mild to moderate hypothyroidism consider:

1. Iodine & Tyrosine (Thorne Research)- Supplies the most important nutrients the thyroid gland needs to produce thyroid hormone.
2. Hypothyroid Chinese Herbal Support- WellVet.Com's own Traditional Chinese Herbal formula.
3. Thyroid Glandular, 2 grain tablets
4. Super EPA

For Dogs with moderate to severe hypothyroidism consider:

1. Hypothyroid Chinese Herbal Support - WellVet.Com's own Traditional Chinese Herbal formula
2. Synthetic Thyroid (levothyroxine)
3. Six-Flavored Tea drink
4. Products that help address any secondary disorders

Look up our information on skin disorders, neurological disorders, diabetes, and other secondary disorders that exist because of hypothyroidism.