Any symptoms of thyroid disease in your dog are cause for concern. The thyroid gland is a master gland that influences your dog’s metabolic processes. Abnormalities may affect your dog’s weight, activity level, and even your dog’s heart rate.
The two main types of thyroid problems are hypothyroidism (underactive thyroid), which is common in dogs, and hyperthyroidism (overactive thyroid), which is common in cats. That doesn’t mean hyperthyroidism can’t occur in dogs. It does, and it shouldn’t be ignored.
Old Dog Thyroid Symptoms
Dogs suffering from the more common hypothyroidism (low thyroid hormones) are usually lethargic, overweight (possibly with odd fat deposits), abnormal hair loss, dry skin, and a greater susceptibility to infections, like ear infections.
With hyperthyroidism, the dog’s metabolism speeds up. You may notice your dog drinking more water (and increased urine), losing weight, constipation, and showing signs of increased activity. With the dog’s overall metabolism too high, many of the dog’s body systems are affected. Some dogs will vomit and have diarrhea along with an increased appetite.
With an abnormal increase in thyroid hormones (hyperthyroidism), your dog may seem restless or even downright hyperactive. This is especially noticeable partly because most dogs with hyperthyroidism are seniors, so just when you expect them to be slowing down, these dogs are revving up.
The heart is also affected. Hyperthyroid dogs may have arrhythmias (irregular heartbeats) or simply a rapid heart rate (tachycardia). Both abnormalities are serious concerns that can have severe consequences.
Diagnosing Hyperthyroidism in Dogs
Bloodwork is the gold standard for diagnosing hyperthyroidism. Many blood panels look at T4 (the thyroid hormone thyroxine) levels as part of the panel. An increase in T4 would be the marker for disease.
If your dog’s T4 is high, more specialized tests are often recommended, such as a full thyroid panel, which includes additional thyroid hormones, including T3 (triiodothyronine), TSH (thyroid stimulating hormone), and TGAA (thyroglobulin autoantibodies).
Causes of Hyperthyroidism in Dogs
One cause of hyperthyroidism is an incorrect dosage of medication given for hypothyroidism. This is why regular checks on thyroid levels are important for dogs on levothyroxine, a medication given to hypothyroid dogs. The veterinarian may need to adjust the hypothyroid dog’s dose.
Dogs can have thyroid cancer. The thyroid gland is located on the dog’s neck in the midline, with lobes on both sides of the trachea. A palpable enlargement is indicative of a tumor and requires further testing.
Most thyroid tumors in dogs are carcinomas. Typically, these cancers do not lead to excess production of thyroxine, but they can cause hyperthyroidism. Breeds suspected of having genetic predisposition for hyperthyroidism include Siberian Huskies, Golden Retrievers, and Beagles.
One study found a link between hyperthyroidism in dogs and a raw meat diet.
Surgery Can Be Curative
If your dog has a thyroid mass, surgery is your best bet, barring any metastatic disease, with the average dog surviving three years after diagnosis.
Your veterinarian may refer your dog to a board-certified surgeon because it is crucial to protect the tiny parathyroid glands that are attached. These glands control calcium regulation. If they are damaged, your dog will need additional medications.
Both thyroid glands are often removed. Most of these dogs will require thyroid supplements for the rest of their lives. Luckily, these medications are fairly inexpensive.
Other suggested treatments include medications to reduce thyroid hormone production and low-iodine diets since thyroid hormones require iodine, but these options have not been very successful. (The radioactive iodine treatment commonly used for hyperthyroid cats is not routinely used for dogs.)
