Hypothyroidism

Hypothyroidism is a common hormonal disease in dogs where not enough thyroid hormone (thyroxine) is produced by the thyroid gland. This gland is located just below the throat. Thyroxine regulates the metabolism of many different parts of the body, and when not enough is made the result is a slower metabolism.

This disease usually develops in middle-aged neutered or spayed dogs (4-10 years).

Causes
The primary and two most common causes of hypothyroidism are:
  Lymphocytic thyroiditis – Auto-immune inflammation and damage of the thyroid gland. The immune system mistakenly attacks the thyroid gland and reduces it thyroxine production.
  Idiopathic thyroid atrophy – Degeneration of the thyroid gland without inflammation and no obvious cause.

Tiredness and lethargy are symptoms of hypothyroidism.
Other less common causes include:
  Thyroid tumors
  Treatment of thyroid tumors, such as surgical removal or radiation therapy and radioactive iodine treatments
  Low iodine (salt) diet – most commercial diets have enough
  Cretinism/dwarfism
  Pituitary gland diseases
  Some medications

Breeds Affected
Breeds most commonly affected are the Golden Retriever, Doberman Pinscher, Greyhound, Irish Setter, Dachshund, Miniature Schnauzer, Great Dane, Poodle, Boxer, Airedale Terrier, Old English Sheepdog and Cocker Spaniel. It can affect mixed breeds as well.

Symptoms
Low thyroid hormone causes a lowering of the metabolic rate. Signs are general, non-specific and long term. Usually dogs with hypothyroidism will have a combination of some of the following signs:
  Lethargy, dullness, depression
  Easily tired
  More time spent sleeping
  Obesity, easy weight gain
  Prone to feeling cold
  Slow heart rate
  Chronic skin problems – chronic skin infections, dry flaky skin, symmetrical thinning of hair, excessive molting
  Infertility
  Diarrhea, constipation
  Other hormonal and neurological signs

Diagnosis
Hypothyroidism isn’t a straightforward disease to diagnose, as the symptoms can be quite varied and vague. It may take a few visits to your veterinarian before a diagnosis is made. A combination of tests are required.

Your veterinarian will start with the following basic steps:
  Question you about your dog’s medical history and symptoms
  Perform a thorough physical examination with extra attention spent on checking the skin

To help determine the disease and to rule out other diseases, extra tests need to be done:
  A complete blood count and biochemistry profile
  A thyroxine level (T4) and possibly a thyroid stimulating hormone (TSH) test
  Other thyroid function tests
  X-rays and ultrasound scans to check for bone and heart abnormalities (if suspected)

Treatment
  Supplementation with synthetic thyroxine tablets for life
  Regular T4 tests to adjust the thyroxine dosage – initially monthly then half yearly when stabilized
  Medications to treat secondary skin infections
  Exercise and weight reduction diet if overweight
  Supplementation with i Love Dogs Green Tea tablets to help weight reduction

The prognosis for dogs treated for primary hypothyroidism is excellent.

Note: Once treatment is started with thyroxine, symptoms of hypothyroidism resolve within a few weeks to 1-2 months. The actual dosage varies from individual to individual due to gastrointestinal absorption and hormonal metabolism, therefore regular testing for T4 levels is important. Over-dosage of thyroxine will result in increased appetite with weight loss, hyperactivity, increased thirst and urinating, panting, anxiety, and diarrhea.

Prevention
There is no prevention for this disease.