Cushing's on the rise? Expert observations on the disease
Our practitioner in the trenches, Dr. Sarah Wooten, has been seeing more cases of Cushing’s disease in dogs in her practice, which made her curious. She got a chance to chat with veterinary endocrinologist Dr. David Bruyette about the trend as well as important updates.
Not in the best spot to watch the video right now? Here’s a quick transcript (just don't forget to scroll to the end for the bonus material!):
Wooten: It seems to me in our practice that we are diagnosing a lot more Cushing’s. And I want to know whether there is an increase in the disease prevalence itself, or just that we’re catching it a lot more?
Bruyette: I think the answer is “Yes” to both. Most of the data now coming out is showing that the incidence of Cushing’s is about 90,000 to 100,000 new cases per year. Some of it’s clearly because veterinarians are just running more tests—they’re picking the disease up earlier. But I think a lot of it has to do with the fact that the dog population is just getting older. And since it’s a geriatric-onset disease, dogs are living long enough to start to manifest signs of Cushing’s.
Wooten: Are there any thoughts as to the cause?
Bruyette: There’s a lot of work being done on the cause of pituitary tumors, both in people and in dogs. With respect to Cushing’s in humans, there are a lot of known genetic defects that occur in the pituitary that result in the disease. We haven’t found any of those mutations in dogs. So the theory now is that in humans it’s primarily a pituitary disorder; in dogs it’s primarily a disease of higher centers in the brain that regulate the pituitary. So it’s more of a neurodegenerative disease of older dogs that causes hyperactivity of the pituitary.
Wooten: Have there been any studies comparing the incidence of Cushing’s disease in our spayed and neutered population vs. our intact population?
Bruyette: Yes, it has been looked at. Unlike the problem we see in ferrets with adrenal disease that are spayed or neutered, we really haven’t seen any difference in the frequency of Cushing’s among spayed or neutered dogs.
Wooten: There is some veterinary literature about how after two years of treatment, the dosages of trilostane that are needed may go down for certain patients, so we’re starting to perform ACTH stimulation testing in these dogs every six months vs. once a year. What’s your advice for the small animal practitioner on that?
Bruyette: Since the launch and since more veterinarians have been using Vetoryl, or trilostane, to treat Cushing’s, we’ve noticed that the initial starting dose that we recommend now has come down quite a bit. So where we were giving maybe 4 to 6 mg/kg, now we’re only giving 1 to 2. I think part of that is related to what you observed, which is that over time as they continue to take an adrenal enzyme blocker, it seems like they develop a cumulative effect and the dose does go down. And I also agree that more frequent monitoring probably makes sense. We usually recommend that they come in every three to four months.
Wooten: You talked about some new treatments that might be coming?
Bruyette: On the human side as well as the veterinary side, we’re really trying to move toward pituitary-directed therapy, whether it’s surgical or radiation. But from a medical standpoint, we’re learning a lot about different receptors that are abnormal or overly expressed in the pituitaries of dogs that have Cushing’s. The primary interest right now is looking at the somatostatin receptor and drugs that block that and the dopamine receptor and drugs that block that. So recently in people, two new drugs have been approved, and we’re hoping to be able to start to use those drugs in dogs.
Bonus material: The Cushing superfan!
We did mention Dr. Bruyette is a Cushing’s disease expert, yes? BUT did you know he’s an avid collector of all things Cushing as well? Hear all about it in this video clip. (It’s only 25 seconds, you have time to watch this one!)