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Hypothyroidism in Dogs. Symptoms and Treatment.


You may have noticed your pup hasn’t been able to shed the pounds like he normally does or he seems to put on weight just by looking at his dinner. Even though you have tried dieting and increasing his exercise, nothing seems to help. In fact, the more you try to exercise your dog, the less he wants to. Is he just getting older and lazy or could there be something else wrong?  In some cases there definitely could be. Hypothyroidism is a fairly common disease in dogs characterized by an inadequate production of thyroid hormone.

What Does Thyroid Hormone Do Anyway?

Before we get into causes, signs and treatments, let’s first talk a little bit about what thyroid hormone does. Thyroid hormone is produced by the thyroid gland, a gland present in the throat. There are two thyroid glands on either side of the trachea. The thyroid gland produces thyroid hormone in response to the pituitary gland in the brain releasing thyroid stimulating hormone. The thyroid stimulating hormone is produced in response to the body telling the pituitary gland it needs more thyroid hormone.

Thyroid hormone’s main function is control of metabolism. This means it controls how cells in the body take in and use nutrients for energy. Increases in thyroid hormone lead to increases in cells taking in and storing glucose, fats, proteins and carbohydrates.  Therefore, thyroid hormone can increase heart rate, muscle contraction, and heat production.

Why the Low Levels?

Hypothyroidism is most commonly acquired, meaning it develops later in life. But it can also be congenital, or present at birth.  Acquired hypothyroidism can occur due to:

  • Inflammation of the thyroid gland, or thyroiditis. This inflammation causes damage to the thyroid gland resulting in reduced production of thyroid hormone.
  • Thyroid cancer can also damage the thyroid gland causing lower hormone levels.
  • Pituitary gland dysfunction is a rare but possible cause of hypothyroidism
  • Sometimes we just don’t know. Referred to as idiopathic hypothyroidism, nobody knows the reason why, it just happens.
  • In some cases, thyroid levels can be low due to above normal amounts of steroid in the blood. The increased steroid decreases the pituitary’s release of thyroid stimulating hormone and therefore thyroid hormone levels.  Increases in steroid can be due to giving steroids for another condition or a disease called Cushings or hyperadrenococorticism.

What Does Hypothyroidism in Dogs Look Like?

Since thyroid hormone has an affect on almost every system in the body, signs of hypothyroidism are widespread. Here are some of the most common complaints by dogs and owners:

  • Lethargy, inactivity or exercise intolerance. Basically, your dog doesn’t have the spring in his step that he used to or he wants to turn around halfway through the morning walk.  These signs are due to decreased energy intake into the cells.
  • Easy keeper. Weight gain or inability to lose weight are very common complaints pet owners have. They feel like they are starving their pooch and he still looks like he just ate three dog’s meals.  Again, this is due to a decrease in metabolism.
  • Dry hair coat, hair loss, or hair that doesn’t regrow after being clipped. Dogs with hypothyroidism are more prone to skin infections that keep returning after treatment.  The pigment of their skin in these areas can change as well.
  • Hugging the heat source. Because thyroid hormone aids in heat production, hypothyroidism can cause your pup to look for alternative sources of heat.
  • Infertility, most commonly noticed in female dogs as failure to come into heat as expected.
  • Some rare cases show up with a generalized muscle weakness causing incoordination.

Most commonly hypothyroid dogs are middle aged.  Signs develop gradually over time and tend to get worse if left untreated.

How Do We Know For Sure it’s Hypothyroidism?

Diagnosis of hypothyroidism is performed with a simple blood test.  Most veterinary clinics can do this test within their own walls, but some may have to send it off to another laboratory.  The blood test is checking the thyroid levels in the blood.  This test can be somewhat unreliable as thyroid levels can be low in healthy dogs at times.  Your veterinarian will have to take your pup’s history, examination findings, and test results into consideration and produce a plan from there.

In some cases, your dog may have to undergo an additional test called a TSH Stimulation test. This test consists of giving your dog thyroid stimulating hormone to see if his body responds with an increase in thyroid hormone.  In dogs with hypothyroidism, there will be no increase.  This test produces the most reliable results, but tends to be more expensive, so use of it varies with each veterinary clinic.

How to Treat Hypothyroidism in Dogs?

So your dog’s blood test came back with lower than normal thyroid hormone, now what?  Fortunately, the treatment for hypothyroidism is quite simple and usually relatively inexpensive.

  • Dogs are started out on a synthetic thyroid hormone such as levothyroxine. Available in a pill that is given twice a day, the synthetic thyroid hormone acts just like your dog’s natural thyroid hormone in his body.
  • Your pup will need to be monitored with regular blood tests to determine the correct dosage. This could take a couple months to get him on the right tract and may need additional adjusting as his weight changes.
  • Fortunately for some dogs, once they get regulated, the levothyroxine dose can be decreased to once a day.
  • Even though the dosage may be decreased over time, your dog will need treatment for life.

Be sure to go in for your pooch’s scheduled rechecks as incorrect dosages of synthetic thyroid hormone can cause the opposite effect and create hyperthyroidism. You should also monitor your dog’s attitude, energy level, and skin issues for improvement once starting therapy. With the correct treatment, all of these signs should decrease over a matter of weeks. Additional secondary treatments include:

  • A low fat diet and exercise program to encourage weight loss. Normal thyroid hormone levels will promote weight loss on their own, but why not speed up the process?
  • Some pups require antibiotics and/or other treatments to help with skin troubles caused by hypothyroidism.
  • Dogs with hyperadrenocorticism need to be treated appropriately for that first. Thyroid hormone levels will return to normal on their own once steroid levels are normal.

The vast majority of hypothyroidism cases in dogs are easily treated and these pooches go onto a normal, happy life. Only certain, rare cases such as dogs that have a tumor of the pituitary or thyroid gland causing the hypothyroidism have a poor prognosis.  Overall, hypothyroidism is a fairly common, easily managed disease as long as dog owners are in tune to their pup and know the presenting signs.

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