(CATS/PET HEALTH) Feline hyperthyroidism is an increasingly common problem in cats over the age of 10, and it’s become one of the most mysterious diseases in veterinary medicine.
Vets regularly screen senior cats for hyperthyroidism nowadays, and typically around 10 percent are found to have the disease.
While there is no known genetic predisposition for hyperthyroidism, studies link the feline disease to polybrominated diphenyl ethers (PBDEs), a common class of flame retardants that have coated the insides of our homes since the 1970s.
For decades, large quantities of chemicals have been routinely added into countless household goods like couch cushions, carpet padding, and electronics. Unsurprisingly, many behaviors suggested to put cats at risk of the disease involve simply being indoors (using cat litter, eating canned food, sleeping on the floor, and even living in a home with a gas fireplace).
So if environmental toxicants are causing health problems in animals, how are they affecting humans? Continue reading below for more on this modern-day disease and how such parallel trends may be more than mere coincidence. — Global Animal
New York Times, Emily Anthes
Most days, the back room of the Animal Endocrine Clinic in Manhattan is home to half a dozen cats convalescing in feline luxury. They lounge in their own individual “condos,” each equipped with a plush bed, a raised perch and a cozy box for hiding. Classical music plinks softly from speakers overhead. A television plays cat-friendly videos — birds chirping, squirrels scampering. Patients can also tune in to the live version: A seed-stuffed bird feeder hangs directly outside each window.
One afternoon in April, a jet-black cat named Nubi assumed a predatory crouch in his condo as a brawny pigeon landed on a feeder. Dr. Mark Peterson, the soft-spoken veterinarian who runs the clinic, opened the door to Nubi’s condo and greeted the 12-year-old tom in a lilting, high-pitched voice. “How are you?” Peterson asked, reaching in to scratch his patient’s soft chin. Nubi, who typically is so temperamental that his owner jokes about needing a priest to perform an exorcism, gently acquiesced, then turned back to the bird. Peterson seemed eager to linger with each of Nubi’s four feline neighbors — Maggie, Biggie, Fiji and Napoleon — but, he warned, “these cats back here are radioactive.”
He meant that literally. The previous day, all five animals received carefully titrated doses of radioactive iodine, designed to destroy the overactive cells that had proliferated in their thyroid glands and flooded their bodies with hormones. These cats are among the millions suffering from hyperthyroidism, one of the most mysterious diseases in veterinary medicine. When Peterson entered veterinary school in 1972, feline hyperthyroidism seemingly didn’t exist; today, he treats nothing else. In the intervening decades, hyperthyroidism somehow became an epidemic in cats, and no one knows why.
“I’ve devoted most of my time in the last 35 years to this,” said Peterson, who noted that he has treated more than 10,000 hyperthyroid cats, “and I still have more questions than I have answers.”
Although definitive answers remain elusive, scientists are narrowing in on one possible explanation: A steady drumbeat of research links the strange feline disease to a common class of flame retardants that have blanketed the insides of our homes for decades. But even as the findings may answer one epidemiological question, they raise another in its place. If household chemicals are wreaking havoc on the hormones of cats, what are they doing to us?
By the time Peterson met Sasha in the fall of 1978, the scrawny tuxedo cat was a regular at the Animal Medical Center in Manhattan. The 15-year-old had lost a profound amount of weight, despite a seemingly insatiable appetite. Her case stumped veterinarians, who had already ruled out many of the obvious culprits, including parasites, irritable-bowel disease and diabetes.
Peterson, who had become restless with his veterinary residency, was spending his time off attending endocrine rounds at New York Hospital. When he heard about Sasha’s symptoms, he thought of the thyroid, a gland that sits at the base of the neck and secretes hormones that regulate metabolism. In humans, weight loss and increased appetite are among the hallmark symptoms of hyperthyroidism, in which the gland churns out huge quantities of hormones, sending the body’s internal systems into overdrive.
Although cats weren’t known to develop the condition, Peterson thought the possibility was worth at least investigating. And so, one afternoon, he ferried Sasha to the hospital, where a sympathetic doctor had agreed to give the cat a thyroid scan. The image was unambiguous: There was a large mass on Sasha’s thyroid. The tumor was benign, but its inexhaustible cells were dumping thyroid hormones into her bloodstream. “We got all excited, and we didn’t know exactly what we were doing, but we removed the tumor,” Peterson says. “And the cat got better and gained like five pounds in six months.”
[quote style=”boxed” float=”right”]It was an astonishing discovery — dozens of pets wasting away from a disease that nobody knew existed.[/quote]It was a happy ending for Sasha, but for Peterson and Gerald Johnson, the gastroenterologist at the Animal Medical Center, it was just the beginning. “Dr. Johnson said, ‘You know, I have these other cases that I haven’t been able to figure out,’ ” Peterson recalls. “So we thought: We’ll get them back. Let’s test them.” They quickly found four more cats with benign thyroid tumors and elevated levels of thyroid hormones. And the more they looked, the more hyperthyroid cats they found. “It didn’t take very long to get a dozen cases, and then 30 cases, and then 100 cases,” Peterson says. It was an astonishing discovery — dozens of pets wasting away from a disease that nobody knew existed.
In the summer of 1979, Peterson presented the first five cases of feline hyperthyroidism to a standing-room-only crowd at a veterinary conference in Seattle. There, he learned that hyperthyroid cats had recently begun turning up in Boston; the vets at Angell Memorial Animal Hospital would soon publish a paper on their first 10 patients. The reports set the veterinary world abuzz and raised some unsettling questions.
“The first, among specialists, was, ‘How did we miss this?’ ” recalls Duncan Ferguson, a veterinarian and pharmacologist who was a co-author of a 1982 paper on the first cluster of cases to appear in Philadelphia. “We can’t believe it just sort of appeared. Is this a new disease?”
It seemed to be. When Peterson later combed through old pathology reports for 7,000 feline necropsies, he found that the thyroid abnormalities he was seeing were rare until the late 1970s. But once the outbreak started, it spread fast. From 1979 to 1983, the vets at the Animal Medical Center saw three cases a month on average; by 1993, they were seeing more than 20. The disease hopscotched across the United States and then the world, striking cats in Canada, Europe, Japan, Australia and New Zealand.
Today, senior cats are routinely screened for hyperthyroidism, and about 10 percent will be found to have the disease. Owners can choose from a variety of treatments, including drugs, surgery or radioactive iodine, which destroys the hyperactive thyroid cells while sparing the healthy tissue. At his two clinics — the one in Manhattan and another in Bedford Hills, N.Y. — Peterson administers radioiodine to more than 300 cats each year. But for all the progress veterinarians have made in diagnosing and treating the disorder, it has been far trickier to determine its origin.
When hyperthyroidism first surfaced in cats, Peterson was confident that scientists would soon make sense of the curious condition. A number of researchers, including Peterson, became epidemiological detectives, searching for dietary, environmental and lifestyle factors that distinguished the hyperthyroid cats from healthy ones, and they turned up many leads. Among the many behaviors that appeared to put cats at risk: spending time indoors, using cat litter, eating canned food, eating fish-flavored canned food, eating liver-and-giblet-flavored canned food, drinking puddle water, sleeping on the floor, sleeping on bedding treated with flea-control products and living in a home with a gas fireplace.
Read the full New York Times article, here: https://www.nytimes.com/2017/05/16/magazine/the-mystery-of-the-wasting-house-cats.html