Dear Dr. Thompson: I have given my cat canned salmon for two years thinking it was a healthy food for her. After a checkup, Katy has an elevated thyroid. I read a letter to you regarding a cat with a thyroid problem, and you mentioned a food product that could cure it. I would greatly appreciate knowing the name of the product to help with her thyroid. I am now cooking most of Katy's food: chicken, ground turkey, and fish, sometimes with garlic and carrots and with cat food. I'm giving her a thyroid product I found on the Internet. Between the cooked food and the supplement, she has become calmer but she still drinks a lot of water and urinates quite a bit.
I am sorry to hear your cat was diagnosed with hyperthyroidism, or an overactive thyroid gland. Her condition stems from a benign growth on the thyroid glands in the neck that over-secrete thyroid hormone. This hormone affects every cell in the body and the most common symptoms people notice are weight loss with a ravenous appetite, vomiting, increased thirst, and frequent urination. High blood pressure, heart enlargement, blindness, or sudden death are all outcomes of untreated or poorly managed hyperthyroidism. However, there are a few items you mention in your question that could have potentially disastrous effects for her in addition to her thyroid disease.
The diet you are cooking may lead to some serious problems. While cats are naturally carnivores, an all-meat diet may not meet all of her nutritional needs. Cats are unable to produce certain amino acids and if her diet is deficient she could develop life-threating diseases such as heart failure. Commercial cat foods are intentionally supplemented with these essential amino acids to avoid problems.
Any home-cooked diet needs to be very carefully prepared and supplemented to provide the complete nutrition cats need. Garlic is toxic to cats because it can trigger damage to circulating red blood cells and serious anemia can develop. The amount of garlic is proportional to the potential adverse effects, but even a small amount can cause serious disease, so please stop giving her garlic.
There can be some options to manage her hyperthyroidism with a special prescription diet, but close monitoring is needed to make sure the toxic levels of the hormone are coming down. This requires periodic blood testing and her condition needs to be closely watched. Early results with the prescription diet are promising but if she has developed kidney problems from her thyroid disease it may not be appropriate.
From what you are describing with her thirst and frequent urination, her condition does not sound well managed. The supplement you are giving is not addressing her thyroid levels and is probably sedating her. Thyroid disease can be successfully treated with multiple therapies and she has the potential to live a long, symptom-free life. However, many issues can arise so I strongly recommend you work with your veterinarian to address her thyroid disease and implement a better nutritional approach for her to avoid serious side effects.
Questions for Dr. Gary Thompson can be emailed to firstname.lastname@example.org or mailed to The Blade, Attn. Ask the Vet, 541 N. Superior St., Toledo, OH 43660. Dr. Thompson regrets that he cannot answer individual letters.