Case Story: Hyperthyroidism in a cat ***Graphic content warning***
Alex, a 15-year-old neutered male cat, came in for a check-up last May due to some noticeable changes in his behaviour and significant weight loss.
During the exam, we couldn’t do much as Alex wasn’t feeling too cooperative (which is totally understandable for a senior cat!), but we did notice a new heart murmur. We decided to schedule a heart scan to get a closer look.
When Alex came in for the heart scan, we were able to examine him more thoroughly because he was lightly sedated. That’s when we discovered that his thyroid gland was unusually large. We did a blood test right away, which showed that his thyroid hormone levels were much higher than normal.
Hyperthyroidism is a common condition in older cats, where one or both thyroid glands (located in the neck) develop a benign tumour that starts overproducing thyroid hormone. This causes symptoms like excessive hunger, weight loss, fast heart rate, and even vomiting.
We also did the heart scan, and while Alex’s heart walls were slightly thickened, there was no sign of heart failure, which was great news. We suspected that the heart changes might be linked to the hyperthyroidism and could improve once the thyroid issue was treated.
We started Alex on medication to manage his hyperthyroidism. The medication did improve his thyroid hormone levels and helped reduce some of his clinical signs. However, his thyroid levels remained higher than we would have liked, even after several adjustments to the medication. Despite the improvement, the levels weren’t low enough, and it became clear that more needed to be done.
After careful consideration, we decided surgery was the best option. About 10-20% of cats with hyperthyroidism may have thyroid tissue located outside the neck (called ectopic tissue), which surgery alone might not fix. However, because Alex’s thyroid gland was so enlarged, we believed surgery could still improve his quality of life and help manage his thyroid levels more effectively even if that was the case.
We removed the thyroid gland and sent it off for analysis. Fortunately, it turned out to be a benign tumour (an adenoma), and his thyroid hormone levels quickly stabilized after surgery.
Today, Alex is doing wonderfully—he’s no longer hyperthyroid, his heart murmur has disappeared, and he’s much happier overall. His owners are relieved to see their sweet senior cat back to his old self!
