Thyroid symptoms in cats

Updated April 17, 2017

When a cat’s thyroid gland begins to malfunction, it is usually a case of it being overactive rather than underactive. Known as hyperthyroidism, the condition results in an overabundance of the thyroid hormone in the blood, and if left untreated, it will lead to heart failure and death. Most cats can be effectively treated with medication and radiation therapy, and some cats may be candidates for thyroid removal surgery. Although hyperthyroidism is more common in older cats, any cat displaying the symptoms should be taken to a veterinarian for a definitive diagnosis.

Weight Loss Despite Good Appetite

A cat who is losing weight despite having a ravenous appetite is showing the hallmark sign of hyperthyroidism. Because the thyroid hormone is responsible for setting the cat’s metabolic rate, an overactive gland will cause the metabolism to move too quickly. Thus, the food the cat eats does not remain in his system long enough for his body to absorb the nutrients, so he loses weight. He will be increasingly hungry, though, because his body is sending him signals that it is starving, inducing him to eat more.

Increased Bowel Movement Frequency

Because the cat is eating more, he will obviously defecate more. Because his metabolism is moving at an increased pace, his body will process and digest food more quickly, resulting in more frequent bowel movements.


A goitre is an enlarged thyroid gland, and can be seen as a swelling at the base of the throat. The gland is butterfly-shaped, and is usually unnoticeable in a healthy cat, but hyperthyroid cats generally will have at least one enlarged lobe.

Poor Hair Coat

Because the cat’s body is not reaping the nutritional benefit from the food he eats, vitamin deficiencies will begin to take their toll. The quality of the coat is one of the first places this will become apparent, as the fur becomes dry and broken, and may fall out in spots. The dry fur may also be itchy, so you may notice your cat scratching more often despite no evidence of fleas or rashes.

Increased Drinking and Urination

The cat’s body is working extra hard on very little fuel at this point, and he will quickly become dehydrated. Just as he is not benefiting from his food, he also may not become fully hydrated when he drinks. His brain will send him signals to drink more, yet he will still not become fully hydrated. The increased water intake will also lead to increased urination, both in volume and frequency, as the liquid simply passes right through with very little being absorbed into the body.

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