There are two main causes of thyroid problems in dogs – both with different symptoms. One type is referred to as Hypothyroidism and the other is known as Hyperthyroidism.Before we go into detail regarding each type lets start by going into a little more detail about the thyroid gland.
There are two thyroid glands that are found below the larynx inside your dog’s neck (attached to the Trachea). This gland releases a hormone that regulates your pets metabolic rate – so when too many hormones are produced or too little then this can cause a variety of symptoms in your pet (a lack or deficiency in the production of the hormone Thyroxine will cause Hypothyroidism and an excessive production will cause Hyperthyroidism).
There is also the Parathyroid gland which is found alongside the thyroid – this produces the Parathyroid hormone which helps to control the calcium in your dog or puppy’s body so it is very important for bone growth.
About Hypothyroidism In Dogs
As previously mentioned this condition is caused by a lack or reduced production of hormones by the thyroid gland.
The most common cause of Hypothyroidism is due to serious problems with the thyroid (where it has been significantly damaged). Other causes of the condition can be as a result of cancer, inflammatory disease, genetics, medication or problems with the pituitary gland and hypothalamus. It is also possible for the condition to develop when the immune system starts to attack and kill the cells in the thyroid gland.
Due to the Pituitary gland and Hypothalamus playing such a large role in how the thyroid hormone is produced we need to explain in a little more detail what these organs do.
The Pituitary Gland is located at the base of the brain and is split in to two parts (the anterior and posterior part).
The anterior part of the Pituitary gland produces a variety of different hormones each playing an active role:
Growth hormone Well this explains what it does i.e. it helps to control how your dog or puppy grows and develops (but specifically up to puberty).
Thyrotropic hormone This plays a large and crucial role in how the thyroid works.
Corticotropic hormone This hormone controls how the adrenal cortex works.
Gonadotropins follicle-stimulating hormone This hormone helps and supports how the eggs are ripened in the ovaries.
Luteinizing hormone This hormone actually causes ovulation in dogs.
Prolactin This hormone will stimulate your dogs mammary glands so that they are able to produce milk.
The posterior part of the Pituitary gland also produces important hormones including…
Anti-diuretic hormone This stops the kidneys from losing too much water.
Oxytocin This enables the uterus to contract during whelping and also stimulates the mammary glands into producing milk.
What Does The Hypothalamus Do For Dogs?
The Hypothalamus acts as a thermostat in your dogs brain helping to control your dog’s temperature but it also plays an active part in how your dog’s appetite is influenced. This organ will also influence urination and how blood is circulated.
Symptoms Of Hypothyroidism In Dogs
There are a number of symptoms of this condition. Basically as a consequence of insufficient hormones being produced that help to control a dog’s metabolic rate (metabolism) and organ activity – symptoms can include…
1. Your dog will probably be lethargic and tired (lacking energy and not keen on exercise).
2. Your pooch may start to put weight on (you will be the first to notice this but speak to your vet as they will have records of your dog or puppy’s weight over the last few months).
3. Your dog’s coat may be really greasy losing it’s shine and condition. Hair loss is another symptom of thyroid problems in dogs. The color of the coat might also change.
4. One of the most common symptoms of hypothyroidism is for dogs to be really affected by the cold. An affected dog might seek warmer areas in the property or always seek to be next to the fire.
5. Some dogs will also experience intestinal problems including constipation and diarrhea.
6. Thyroid problems in dogs (Hypothyroidism) can also lead to eye problems including ulcers or problems with the surface of the eye (i.e. the cornea).
7. There may also be problems with reproduction including reduced fertility.
8. Thyroid problems in dogs (thyroid disease) is also sometimes associated with laryngeal paralysis and megaoesophagus – this can often be detected when your pet has heart disease or a low heart rate.
Diagnosis of Hypothyroidism In Dogs
This condition is normally diagnosed through the vet recognising the symptoms but to get a firm diagnosis blood tests will need to be taken. Blood tests will normally show some signs of thyroid disease including anemia.
Hormone tests can also be undertaken by the vet where thyroid problems will normally show low levels of thyroid hormones being circulated – but high levels of the hormone that triggers their release (but is not able to because the thyroid is not functioning properly).
Another method utilized by vets to diagnose thyroid problems in dogs is to test if the thyroid gland is working properly by injecting a thyroid-stimulating hormone – so if the gland does nor respond as it should the vet will be able to determine that it is not functioning properly.
How Hypothyroidism Is Treated In Dogs
Treatment for Hypothyroidism will normally consist of the vet undertaking thyroid replacement therapy – this might involve a replacement synthetic hormone being prescribed (one of the best known is Thyroxine).
This is a very effective treatment for thyroid problems in dogs and will normally result in a very quick rapid positive response. Each individual dog will need different doses depending on how they respond. Blood tests will need to be taken to check your dog’s thyroid hormone levels – so the medication dose will need to change depending on how your dog responds to the treatment.
At the start of the treatment process your poochs blood will need to be tested every four weeks but as things improve tests can be reduced to every six months.
Hyperthyroidism – This condition occurs when excessive amounts of the hormone thyroxine are produced (the opposite of Hypothyroidism). This can lead to a number of symptoms in your dog including weight loss, excessive thirst and a huge appetite. It is not uncommon for dogs to eat so fast that they end up being sick. Your pooch may also develop diarrhea.
Your dog may also become really restless, hyperactive with lots of energy – this can also cause an increase heart beat that may result in heavy breathing.
The most common cause of Hyperthyroidism is due to cancer (normally cancer that has directly affected the thyroid gland).
Diagnosis of thyroid problems in dogs – Hyperthyroidism… – This condition is normally diagnosed through the vet looking at the physical symptoms, clinical history and through blood tests. The vet will speak to the owner to determine whether your dog is experiencing any of the above symptoms (and check for an increased heart rate and an enlarged thyroid gland).
When the blood tests have been examined they may show higher levels of red and white blood cells. It is also not uncommon for the blood tests to show signs of creatine, glucose, ALT (a liver enzyme) and phosphorus.
However, one of the best methods to check for Hyperthyroidism is through FT4 testing, this is also a blood test but is very reliable at determining how the thyroid is functioning.
There are a variety of ways to treat this condition – some more invasive than others. Medication can be utilised to reduce the amount of hormones being produced. After a few weeks of treatment your dog’s thyroid hormone levels should have returned to normal.
One of the most successful methods to treat this condition is through a radioactive iodine being prescribed. This is often used to kill the cells in the thyroid that are too active.
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