The thyroid gland is found in the neck and is made up of two lobes. This gland regulates the speed at which other body processes work. The thyroid gland is part of a three gland system including the hypothalamus and the pituitary. Problems in either of these glands can negatively impact the amount of hormone released by the thyroid. Diseases such as Hypothyroidism (too little hormone) and hyperthyroidism (too much) are a direct result of this gland system not operating properly.
Dogs with this condition are suffering from the a tumor destroying the thyroid or the pituitary gland. Since hypothyroidism in dogs is related to less hormone, this directly relates to a slowing down of body systems. Specifically this means that there is a drop in production of thyroxine (T4) and 3,5,3 triiodothyronine (T3). One in 250 dogs develop the condition. The mean age is 7 years old.
Source: Oxford Labs
The disorder is referred to as being primary (caused by a problem in
the thyroid gland, in a form called lymphocytic thyroiditis and
Idiopathic thyroid atrophy), secondary (caused by another process in
the dog such as a pituitary gland problem), or tertiary (caused by the
part of the brain called the hypothalamus).
- Lymphocytic thyroiditis: When the thyroid is infiltrated by
lymphocytes, which are small white blood cells that help the immune
- Idiopathic thyroid atrophy: Where the thyroid gland wastes away
with no known cause
- Neoplasia: Cancerous tumor growth
Disease: Abnormal pituitary function
- Congenital problems
- Iodine deficiency due to dietary problems
- Iatrogenic: caused by a surgical procedure or radiation therapy
Large breed dogs have a higher incidence of hypothyroidism:
- Doberman Pinscher
- Golden Retriever
- Labrador Retriever
- Cocker Spaniel
- German Shepherd dog
- Mixed breeds
Dog Thyroid Symptoms
The behavioral, gastrointestinal, cardiovascular, nervous, neuromuscular, ocular (eyes), skin and reproductive systems can be affected. Typical symptoms are:
- hair loss
- weight gain
- mental dullness
- decrease in activity
- can't keep warm
- dry skin
- dry or dull coat
- skin infection/skin pus
- ear canal infection (otitis externa)
- skin thickening and puffy eyes (rare)
- Facial paralysis
Symptoms are similar to euthyroid sick syndrome (normal thyroid function accompanied by abnormalities in the level of hormones in the body, usually seen in sick patients), which needs to be differentiated by hypothyroidism before a final diagnosis can be made.
Diagnosis for this type of dog thyroid problem involves measuring the amount of thyroid hormone being produced.
Thyroid problem in dog treatment due to hypothyroidism involves replacement therapy of the hormone for the life of the patient. It may take some experimentation by your veterinarian to get the level right. Dogs will have a normal lifespan after treatment and any symptoms should clear. Dogs will be tested for thyroid function 6 weeks after starting therapy, then every 6 to 8 weeks for 6 to 8 months, then 2x per year.
If the condition is left untreated dogs can develop myxedema (skin swelling), myxedema coma or atherosclerosis (build up of plaque in the blood vessels).
Hyperthyroidism means that your dog is producing too much thyroid hormone. There is a higher incidence of the disease in Labrador Retrievers. The condition is usually caused by a dog thyroid tumor and is a very aggressive form of cancer, with 10% of dogs with a thyroid carnicoma being hyperthyroid (1). A form of hyperthyroidism in dogs, Iatrogenic hyperthyroidism is caused by over supplementation, but is rare.
This excess hormone causes the metabolism to speed up resulting in:
- weight loss
- desire to eat more
- faster heart rate
- increased urination
- shortness of breath
Diagnosis is made by measuring the levels of thyroid hormone in your dog's body.
Treatment of hyperthyroidism involves surgically removing the diseased portion of the thyroid and then using hormone replacement therapy if needed. Chemotherapy, radioactive iodine therapy are also used depending on the tumor size, how invasive it is in surrounding tissue and if it has started to metastasize or spread to other organs.
Holistic veterinarians believe that in the case of hypothyroidism, that natural medicine (herbal remedies) can be used to naturally stimulate hormone production vs. the man made synthetic kind prescribed be veterinarians. It might be worth discussing with your veterinarian alternatives such as the one made by Pet Alive called Thyro-Pet.
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(1) Feldman EC, Nelson RW. Canine thyroid tumors and hyperthyroidism. In: Feldman EC, Nelson RW. Canine and Feline Endocrinology and Reproduction. St. Louis: WB Saunders, 2004, pp 219-249.
(2) Feldman EC, Nelson RW. Hypothyroidism. In: Feldman EC, Nelson RW. Canine and Feline Endocrinology and Reproduction. St. Louis: WB Saunders; 2004, pp 86-151.
Merck/Merial Manual for Pet Health
The Mechanic's Guide to Your Patient's "Idle System": Thyroid
The Pet Hospital, Portland, OR, USA.