Link to Thyroid Cancer in Humans May be Found in Cats
A new study on thyroid cancer in people provides support for the idea that the rising incidence of the disease is not simply a result of improvements in doctors’ ability to detect it. In other words, more people really are developing thyroid cancer than they did in the past.
“What,” you might be wondering, “does this have to do with pets?”
From a literal point of view, nothing, but hyperthyroidism in cats, which is almost always caused by a benign thyroid tumor, is also on the rise. In fact, it is now thought to be the most commonly diagnosed feline endocrine (hormonal) disease. I wonder if a common cause might be behind the rising incidence of thyroid disease in people and cats.
I’ve reported previously on a possible link between feline hyperthyroidism and exposure to polybrominated diphenyl ethers (PBDEs) that are used as flame retardants in furniture, electronics, and other consumer products. PBDEs have been shown to have an adverse effect on many parts of the body, including the endocrine system and were found to be present in house dust taken from the homes of hyperthyroid cats at higher levels in comparison to the homes of cats with with normal thyroid levels. This research certainly doesn’t conclusively link PBDE exposure to the development of thyroid disease in cats, but it does raise the possibility.
Cats have been sentinels for human disease in the past. One especially disturbing episode occurred in the 1950s in Japan. For several years, residents of the town of Minamata had noticed that cats residing in the area were becoming sick and dying in a very unusual manner. They called the condition “dancing cat disease.” Affected cats moved in erratic and bizarre ways, developed seizures, and died. A couple of years later, people began to experience essentially the same symptoms. The causative agent was eventually determined to be mercury that was being released into the ocean by a factory in the town and was becoming concentrated in the seafood that the town’s residents (human and feline) were eating.
Medical doctors and veterinarians are beginning to have a greater appreciation for just how interconnected the health of our patients are. I can’t begin to recall the number of times I’ve had conversations with owners about a new diagnosis in a household pet only to be told, “How weird. I (or someone else in the family) have the same thing.” I’m sure the majority of these cases are simply coincidental or have something to do with owners and pets sharing similar lifestyles (e.g., poor eating and exercise habits). But, I wouldn’t be surprised to learn in the future that a few might be related to shared exposures to environmental contaminants or to as of yet undiagnosed infections that can cross species barriers.
It would behoove us all to pay attention when the health of a group of animals takes a turn for the worse. You never know who might be next.
Dr. Jennifer Coates
Characteristics of Incidentally Discovered Thyroid Cancer. Yoo F, Chaikhoutdinov I, Mitzner R, Liao J, Goldenberg D. JAMA Otolaryngol Head Neck Surg. 2013 Oct 10.