Obesity and Diseases

Hypothyroidism and Cushing's Disease

Most cases of canine obesity are simply a matter of too many calories and not enough exercise. If, however, your dog is overweight despite not eating all that much, it is important to rule out a medical reason for your dog's weight.

Obesity and diseases are linked in more ways than one, and while being overweight can trigger a host of disorders, the reverse is also true: Disease can cause obesity. In this article, I will be discussing the two most common medical reasons for canine obesity: hypothyroidism and hyperadrenocorticism (Cushing's disease).

Hypothyroidism in Dogs

Hypothyroidism occurs when your dog's thyroid gland produces insufficient thyroid hormones. In the vast majority of cases (95%+), the thyroid gland is attacked by the dog's own immune system, resulting in the gradual destruction of the gland. This condition is known as autoimmune thyroiditis. When the damaged thyroid gland is no longer able to meet the body's demand for thyroid hormones, the dog becomes symptomatic.

Since the thyroid gland is instrumental in regulating your dog's metabolism, many symptoms of hypothyroidism are metabolic in nature. The most common symptoms are lethargy, weight gain without associated increases in food consumption, hair loss and poor coat condition. These symptoms affect about two-thirds of hypothyroid dogs.

Other symptoms include hyperpigmentation of the skin, skin and ear infections (very common), cold intolerance, depression, sad facial expression, loss of hair on the tail, head tilt, mental dullness, decreased heart rate, muscle weakness, seizures, exercise intolerance, reflux gastritis, anemia, high blood cholesterol, reproductive problems, and behavioral issues such as fearfulness and aggression.

While hypothyroidism can occur in all dogs, some breeds are more susceptible than others. Golden Retrievers, Doberman Pinschers, Greyhounds, Irish Setters, Cocker Spaniels, Dachshunds, Boxers, Labrador Retrievers, Miniature Schnauzers, and Airedale Terriers seem to be particularly likely to develop hypothyroidism.

The disease occurs more commonly in medium and large breed dogs, and is unusual in toy breeds. Spayed females appear to be more susceptible than intact ones, and purebred dogs are more likely to be affected than mixed breeds. Most hypothyroid dogs are between the ages of 4 and 8 at the time of diagnosis.

The good news is that hypothyroidism is eminently treatable.

Upon diagnosis, your vet will prescribe thyroid replacement hormone that your dog will need to take every day. Once treatment has begun, your dog's metabolic rate will normalize, and the extra weight will start to come off. Other symptoms will also begin to disappear. While your dog will need to be on thyroid replacement hormones permanently, dogs with hypothyroidism who are receiving treatment can live long, healthy lives.

Cushing's Disease in Dogs

Hyperadrenocorticism or Cushing's disease refers to the chronic overproduction of adrenal hormones, specifically corticosteroids.

The most common variant is Iatrogenic Cushing's Disease which is caused by the overuse of corticosteroids such as prednisone. This type of Cushing's disease is curable by slowly withdrawing steroid medications. It's critical that withdrawal be very gradual to give the adrenal glands time to recover.

Things get more complicated with naturally-occurring Cushing's disease. Things get more complicated with naturally-occurring Cushing's disease.

The most common type of naturally-occurring Cushing's disease in dogs (approximately 80-85% of all cases) is pituitary dependant hyperadrenocorticism, which is caused by tiny tumors of the pituitary gland that make the adrenals go haywire. The tumor makes the pituitary gland secrete excessive amounts of ACTH, a hormone that promotes the adrenal gland's production of corticosteroids.

The remaining 15-20% of naturally-occurring Cushing's disease cases in dogs involve adrenal-based hyperadrenocorticism. This form of Cushing's disease is caused by an adrenal tumor that also promotes overproduction of corticosteroids.

Cushing's disease typically affects middle-aged and older dogs, and initial symptoms are often mistaken for normal signs of ageing. Key symptoms include increased thirst and urination, increased appetite and weight gain, a potbellied appearance, loss of muscle tone (particularly in the abdominal area), redistribution of fat (dogs with Cushing's disease may be bony around the head and spine, but flabby in the belly area), hair loss, dull coat, thin skin that's easily damaged and prone to infections, hind-end muscle weakness, exercise intolerance, excessive panting, lethargy, and hard lumps in the skin.

Some dogs with Cushing's disease have many of these symptoms, while others have just one or two.

When Cushing's disease is caused by an adrenal tumor, the surgical removal of the tumor is sometimes an option. Pituitary dependant hyperadrenocorticism, however, is always treated with drugs (I use Vertryl). While the disease is not curable, it is manageable. Symptoms typically begin to disappear within just a few weeks of commencing treatment.

Canine Obesity and Disease

Dogs with hypothyroidism frequently gain weight despite eating very little. Weight loss efforts are typically futile. It seems as if no matter how much you reduce your dog's food intake, the weight just isn't coming off.

Dogs with Cushing's disease, on the other hand, often have a ravenous appetite that makes them eat everything in sight, supplementing their meals in all sorts of ways. You may find your dog stealing food from the kitchen counter or from other dogs in the household, raiding the garbage, even eating stools (coprophagia).

Interestingly, canine obesity resulting from diseases such as hypothyroidism and hyperadrenocorticism is actually easier to treat than obesity caused by overfeeding and inadequate exercise.

Im my exsperience virtually every single one of my canine obesity success stories involves a dog with hypothyroidism or Cushing's disease who lost weight and kept it off as a result of receiving treatment for the underlying disease. It's unfortunate that more dog owners aren't committed to making the diet and lifestyle changes necessary to eliminate canine obesity that's not caused by disease.

If you suspect that your dog may be suffering from hypothyroidism or Cushing's disease, please ask your veterinarian to screen your dog for these diseases. Once diagnosed, treatment will allow your dog to lose the excess weight and improve your dog's overall quality of life.