Hypothyroidism: What is it?
Drs. Foster & Smith Educational Staff

Hypothyroidism is a common problem in dogs. The thyroid gland has a number of different functions, but it is most
well known for its role in regulating metabolism. Hypothyroidism is the condition that occurs when not enough thyroid hormone is produced. It causes a wide variety of symptoms, but is often suspected in dogs that have weight gain or obesity and suffer from hair loss and skin problems.

Hypothyroidism is easy to diagnose with a blood test that checks the level of various thyroid hormones including T3 and T4. Many dogs suffer from a low thyroid hormone level for years without treatment. If your dog has chronic recurrent skin problems, she may be suffering from hypothyroidism.

There is no specific symptom that is diagnostic for hypothyroidism. There are, however, several symptoms that when combined together make the veterinarian more suspicious that the pet has hypothyroidism. These include:

  • Lethargy/mental dullness
  • Hair loss
  • Weight gain/obesity
  • Dry hair coat/excessive shedding
  • Hyperpigmentation of the skin
  • Cold intolerance
  • Slow heart rate
  • High blood cholesterol
  • Anemia

Treatment consists of putting the dog on a daily dose of synthetic thyroid hormone called thyroxine (levothyroxine), which is available in brand names such as Thyrozine or Soloxine or in a generic form. Drs. Foster & Smith's Pharmacy can fill your dog's thyroxine prescription quickly and economically when your veterinarian calls, mails, or faxes it in.

What dogs commonly get hypothyroidism?
Hypothyroidism most commonly develops in middle-aged dogs between the ages of 4 to 10 years. The disorder usually affects mid to large size breeds of dogs, and is rare in toy and miniature breeds. Although hypothyroidism can occur in either sex, spayed females appear to develop it more often than intact females.

rarely occurs
in cats.
Some breeds that appear to be predisposed hypothyroidism include:

  • Golden Retriever
  • Doberman Pinscher
  • Irish Setter
  • Miniature Schnauzer
  • Dachshund
  • Cocker Spaniel
  • Airedale Terrier

Dosage and frequency of administration of this drug varies depending on the severity of the disease and the individual response of the animal to the drug. A dog is usually placed on a standard dose for his weight and then blood samples are drawn periodically to check his response and then the dose is adjusted accordingly. Once therapy is started, the dog will need to be on treatment for the rest of his life. Usually after the treatment is started, the majority of the symptoms resolve. Contact your veterinarian if your dog experiences increased drinking, urination, and appetite, or exhibits behavior changes while taking a synthetic thyroid hormone.

If you suspect your dog might have hypothyroidism, schedule a veterinary appointment for the necessary diagnostic tests.