Hypothyroidism

Image of a dog.

Hypothyroidism is the natural deficiency of thyroid hormone and is the most common hormone imbalance of dogs. This deficiency is produced by several different mechanisms. The most common cause (at least 95% of cases) is immune destruction of the thyroid gland. It can also be caused by natural atrophy of the gland, by dietary iodine deficiency, neoplasia (primary or metastatic) of the thyroid gland or (rarely) as a congenital problem. Hypothyroidism is most common in medium to large breeds of dogs that are middle aged (4 to 10 years) but can occur in any dog.

Hypothyroidism is extremely rare in cats and is most commonly seen in cats following bilateral thyroid removal or radioactive iodine therapy for hyperthyroidism. This is often transient and usually does not require therapy. Rarely cats can have congenital hypothyroidism.

Thyroid hormone serves as a sort of volume dial for metabolism. Since virtually every cell in the body can be affected by thyroid hormone it is not surprising that reduced levels of thyroid hormone can lead to symptoms in multiple body systems. A recent published survey of hypothyroid dogs showed the following percentages of symptoms:

88% had some kind of skin abnormality
40% had hair loss (often on the tail or on both sides of the trunk and flanks ).
22% had skin infections
14% had dry brittle coats with hair that could easily be pulled out
49% were obese
48% were described as lethargic or listless at home
36% were anemic
80% had an increase in blood cholesterol

Hypothyroidism is treated with the oral administration of thyroid hormone, usually given twice daily for the life of the dog. Periodic blood testing is recommended; it is important to know if the medication dose is too low or too high. Thyroid supplement is a safe medication but if it is not given in sufficient doses the patient will not be adequately treated. If the dose is too high excessive water consumption, weight loss, and restlessness can result. Once a pet is started on thyroid supplementation, it is recommended to check a T4 level in two to three weeks, with the blood draw between 4 to 6 hours after the morning dose.Once the correct dose is found, it is recommended to perform a T4 every six to twelve months.

Hyperthyroidism in Cats

This is a very common disease of the middle aged to older cat. A tumor (97% are benign) on the thyroid gland starts producing too much thyroid hormone. Symptoms are usually weight loss in spite of eating well and vomiting. Other signs you might see are diarrhea, a dull and flaky hair coat, and personality changes. This disease usually can be easily diagnosed with a blood test, although occasionally we need a special test called a technesium scan to diagnose the early, borderline cases.

There are three basic methods of treatment: radioactive iodine, surgery, or an oral medication called methimazole (Tapazole). For most cats, the best treatment is radioactive iodine. In 97% of the cases, it is a one-time treatment. The biggest disadvantage is that the treatment needs to be done at a special facility, and the cat needs to be hospitalized for usually 5 to 10 days. In the past, surgery was a common treatment, but it is performed less frequently as the problem seems to recur on the other gland. Treating with Tapazole is also common, but has the disadvantage that it is life long and the cat needs blood tests to monitor the thyroid level and to check for adverse effects.

The disease of hyperthyroidism can actually help the kidneys. If the cat has both kidney disease and hyperthyroidism, it is not a candidate for radioactive iodine and the dose of Tapazole may need to be adjusted. Kidney tests are also monitored when a cat is being treated for hyperthyroidism.

Your First Visit is FREE

Office Hours

Monday:

8:00 am-7:00 pm

Tuesday:

8:00 am-7:00 pm

Wednesday:

8:00 am-7:00 pm

Thursday:

8:00 am-5:30 pm

Friday:

8:00 am-5:30 pm

Saturday:

8:00 am-2:00 pm

Sunday:

9:00 am-2:00 pm

Location

Find us on the map

Testimonial

  • "Countryside is wonderful!!! I take all three of my cats here, and I'm always so impressed with how they accommodate for each cat based on their personalities. They handle each one according to their unique needs. My most timid female is getting over a UTI. After they weighed her in the back, they brought her back over to me loosely wrapped in a blanket that felt fresh out of the dryer! I absolutely LOVE that attention to detail and genuine care that my furkids receive here."
    Melissa D. / Yorkville, IL

Featured Articles

Read about interesting topics

  • Fish

    If you’re thinking of getting a pet fish, you should know that your veterinarian has a lot of good advice about pet ownership. Fish can be very rewarding as pets, and you just may be surprised about how much fish actually interact with their owners. Here’s more valuable information about choosing ...

    Read More
  • Caring for Senior Cats

    Thanks to advancements in veterinary care, today’s cats can live well into their teen years. It is not uncommon for cats to live to be 18 or even older. However, in order for cats to live a long full life, they need proactive veterinary care to stay healthy. As cats age, they are at greater risk for ...

    Read More
  • Feline Stomatitis: Treatments

    Cats rarely display their pain, but cats with feline stomatitis are often the exception. If your cat appears to have mouth pain, is reluctant to eat, doesn't want to groom, is drooling, and doesn't want you to open its mouth, it may be suffering from this debilitating, degenerative oral condition, and ...

    Read More
  • Feline Leukemia Virus: What You Need to Know

    Feline leukemia (FeLV) is a virus that weakens your cat's immune system. Unfortunately, when the immune system does not function properly, your cat may be more likely to develop other diseases, such as cancer and blood disorders. How Cats Contract Feline Leukemia Cats get feline leukemia from other cats. ...

    Read More
  • Family Cats and Pregnant Women: Take Measures to Prevent Toxoplasmosis Infection

    Nothing must spoil the joys of becoming a new parent. Not even your pets. But family cats with normal, every day habits can pose a risk to expectant women. Women's immune systems can be disturbed by a parasite carried in fecal matter. If you're the primary caretaker of your family's feline friend it ...

    Read More
  • Create an Environment Your Cat Will Love

    The Journal of Feline Medicine and Surgery confirms that feline emotional wellbeing, behavior and physical health are a result of how comfortable they are in their environment. Understanding how our cats interact with their environment can help us create a space for owners and cats to mutually thrive ...

    Read More
  • Catnip: Why Cats Love It

    Few things stimulate a cat's pleasure faster than catnip. Exposure to this simple herb can reveal a new side to their feline personality. Many cats will go crazy at the smell of this plant. Catnip has a reputation of being a feline drug and many cat owners wonder if it is safe to give it to their pet. ...

    Read More
  • Zoonosis

    Zoonosis refers to diseases that can be transmitted to humans from animals. In particular, they occur when an infected animal passes on bacteria, parasites, fungi or viruses to humans through scratches, saliva, feces and urine. Vectors (e.g., organisms like fleas and ticks) can also carry zoonotic diseases ...

    Read More
  • Sugar Gliders

    Thinking of getting a sugar glider? These tiny marsupials are energetic and friendly, making them popular choices as pets. Though they weigh less than a half-pound, they're more closely related to kangaroos than they are flying squirrels. If you think a sugar glider would make an ideal pet for your family, ...

    Read More
  • Epilepsy

    Epilepsy (often referred to as a seizure disorder) is a chronic neurological condition characterized by recurrent unprovoked seizures. It is commonly controlled with medication, although surgical methods are used as well. Epileptic seizures are classified both by their patterns of activity in the brain ...

    Read More

Newsletter Signup

Sign up for more articles