Unlike dogs, who most often have hypothyroidism (or decreased production of thyroid hormone), cats with thyroid disease have hyperthyroidism, or the excess production of thyroid hormone. Hyperthyroidism is the most common hormone disorder in cats. It most often affects older cats, with more than 10% of cats 10 years and older diagnosed with hyperthyroidism.
The most common signs and symptoms of hyperthyroidism in cats are weight loss despite an increase in appetite; gastrointestinal disturbances, such as vomiting and diarrhea; high blood pressure; increased body temperature; increased heart and breathing rates; and changes in urination. There may also be changes in activity level (such as hyperactivity) and attitude. A combination of increased appetite, weight loss, and sudden, unexpected bursts of energy in an older cat points to a diagnosis of hyperthyroidism. Hyperthyroidism is diagnosed with a blood test.
There is increasing evidence that flame retardants have a role in the development of hyperthyroidism, with studies showing that hyperthyroid cats have higher blood levels of flame retardants than cats with normal thyroid function. One study revealed blood levels of flame retardants 20- to 100-fold higher in cats than in humans. In a third study, flame retardant chemicals in the dust of homes of cats with normal thyroid levels was 510 to 4900 ng/g, but 1,100 to 95,000 ng/g in cats with hyperthyroidism.
Flame retardants are commonly added to many consumer products, such as polyurethane foam products (upholstered furniture, mattresses, pillows, pet beds), carpet padding, auto seat covers, kitchen appliances, fans, water heaters, computers and related equipment and supplies, TVs and TV remote controls, video equipment, blow dryers, and cell phones. Flame retardants have even been found in pet foods.
Flame retardants leak from consumer electronics when they heat up during normal use and from foam items when pets lie on them. There also may be high concentrations in dust particles in the living environment. To minimize exposure of your cat to flame retardants, replace foam items when they begin to deteriorate, do not allow cats in areas where carpet is being removed, consider replacing instead of reupholstering furniture on which the foam has deteriorated, and do not repurpose old broken down foam cushions to be used as a pet bed. Vacuums and air purifiers with HEPA filters may trap small dust particles containing flame retardants.