By Dr. Becker
Feline hyperthyroidism has reached epidemic proportions in the U.S. since it was first described in 1979. It's the most common endocrine disorder of housecats, with over 10 percent of kitties over the age of 10 diagnosed with the disease. The sudden appearance and rapid increase in cases of hyperthyroidism in both humans and cats has generated a great deal of research into potential causes.
A study published last year in the Journal of Feline Medicine and Surgery1 identifies the concentration of iodine in commercial cat foods as a likely contributing factor to the high rates of disease in geriatric housecats.
Study Results Show Dramatic Fluctuations in the Iodine Content of Commercial Cat Foods
For the study, cat foods were purchased between November 2008 and March 2009 from pet supply stores and supermarkets in three different regions of the U.S.
The foods were nationally marketed adult cat and kitten foods, as well as "therapeutic" diets. In total, 112 brands of over-the-counter and prescription diets were purchased as follows:
- 71 canned foods, including 1 kitten and 6 therapeutic formulas
- 19 pouched, including 2 kitten formulas
- 22 dry, including 1 kitten and 3 therapeutic formulas
Eight brands and 2 supermarket varieties were tested. The daily iodine intake of an average 10-pound cat or 3-pound kitten was calculated based on manufacturer feeding instructions. Variations were found in iodine concentrations across packaging types, brands, seafood ingredients, and intended use (therapeutic or not). Canned foods showed the most dramatic variation, with iodine intakes ranging between 0.05 mg/day and 9.6 mg/day.
According to study authors, these results suggest the inconsistency in iodine concentrations may lead to development of clinical hyperthyroidism, especially in cats that are first fed iodine-deficient diets, and then later in life are fed diets containing excessive iodine.
"Manufacturers should strive to provide adequately supplemented iodine concentrations that are as uniform as possible across all product lines and regions," study authors conclude.
Symptoms of Hyperthyroidism
About half the cats that develop hyperthyroidism have an increase in appetite. About 90 percent with the disease ultimately lose weight because one of the side effects of too much circulating thyroid hormone is an increase in metabolism rates.
Other symptoms include high blood pressure, frequent vomiting, increased body temperature, heart and respiration rates, and hyperactivity.
A combination of increased appetite, weight loss and sudden, unexpected bursts of energy in an older cat is a definite sign you might have a kitty with hyperthyroidism.
Make an appointment with your veterinarian as soon as possible. The disorder can be diagnosed with a simple blood test.
Traditional treatment of feline hyperthyroidism involves medical management (with drugs), surgery to remove the thyroid gland, or radioactive iodine treatment.
Of course, I always recommend investigating non-toxic alternative therapies first, before resorting to drugs, surgery, or radioactive iodine. There are many natural remedies that can help manage your kitty's condition if it's caught early, including homeopathic remedies, herbal remedies, nutraceuticals, and acupuncture.
Preventing Hyperthyroidism in Your Cat
Recommendations for helping to prevent thyroid disease in your favorite feline:
- Feed a balanced, preferably raw, species-appropriate diet. This will dramatically reduce all concerns about the iodine content in processed cat food. If you prepare a balanced, homemade diet for your cat you have complete control over iodine levels in your pet's food.
- Avoid feeding your cat a fish-based diet. Seafood is a very rich source of iodine, but cats aren't designed to process a lot of iodine.
- Also avoid feeding soy products to your kitty, as they have been linked to thyroid damage.
- Rid your environment of flame retardant chemicals (polybrominated diphenyl ethers, or PBDEs). Recent studies have linked these chemicals in house dust to the growing problem of thyroid disease in pet cats.
I also recommend checking your cat's thyroid levels annually after the age of 10.