The Canine Thyroid Gland:
If the thyroid does not produce the needed amount of hormones, the metabolism slows and many of the body's normal processes are disrupted.
Hyperthyroidism (overactive thyroid) occurs in cats, but is not typically seen in dogs. Unfortunately, an overactive thyroid in a dog is usually a sign of thyroid carcinoma, a cancerous thyroid tumor.
Causes of Hypothyroidism in Dogs:
Hypothyroidism can occur in a dog of any age, but it is most commonly seen in dogs from four to ten years of age. Gender does not appear to affect risk for hypothyroidism, but some evidence suggests that the disease can occur more commonly in spayed females than intact females. In rare cases, hypothyroidism may be congenital, meaning the disease was present at birth.
Be an advocate for your dog's health by visiting your veterinarian often and taking steps to keep your dog healthy. You may be able to help detect hypothyroidism before it becomes a serious heath problem.
Canine Hypothyroidism Symptoms:
- Obesity/weight gain
- Hair loss on body and/or tail (rat tail appearance)
- Dull, dry haircoat
- Skin issues, such as infection or flaking
- Otitis (ear infection)
- Lethargy and/or weakness
- Behavioral changes
One or more of the above symptoms may occur in hypothyroid dogs, but even dogs with no symptoms can have the disease. For this reason, your dog should visit the vet for a wellness exam and routine blood work at least once or twice a year.
Diagnosing Hypothyroidism in Dogs:
Your vet may recommend other blood tests before making a definitive diagnosis. These include measurement of free T4 (the T4 circulating "freely" through the bloodstream) and TSH. Low levels of free T4 are consistent with hypothyroidism. High levels of TSH also indicate hypothyroidism because the pituitary gland will often produce excess TSH in an effort to stimulate the thyroid gland.
Not all cases of hypothyroidism cause abnormal levels in all three primary tests. Hypothyroidism is diagnosed with a combination of blood tests and patient history. Additionally, there are other diseases that cause similar symptoms, so what seems like hypothroidism at first could be a completely different issue. This is why it is important to communicate with your vet. Discuss all of your pet's symptoms and ask about your diagnostic options.
Hypothyroidism Treatments:
The good news is that there are virtually no side effects associated with the usage of thyroid supplements. As with any medication, accidental overdose can occur. Symptoms of overdose include excess drinking and urinating, restlessness, panting, diarrhea and increased appetite.
Hypothyroid dogs must be treated for life. While the cost of thyroid supplements is fairly low, it does add up over time. Expect to spend about $15-30 per month on medication (depending on dosage and brand). This does not include the cost of periodic blood monitoring.
There are no herbal, homeopathic or home remedies that are effective as alternatives to synthetic thyroid hormone supplements. However, some remedies may be helpful in conjunction with thyroid supplementation. Talk to your vet about the options for your dog.
Monitoring the Hypothyroid Dog:
Be sure to keep track of changes in your dog's health, appearance or behavior. Contact your vet if you notice any signs of illness, particularly those signs associated with hypothyroidism or thyroid supplement overdose.
Fortunately, most dogs with hypothyroidism can lead long, healthy lives when properly treated and monitored.

