To be honest, he’s become a lot like my husband.” Danny the Dachshund was 10 years old, had put on an extra 5 pounds, was losing his hair, slept all day and had to get up to pee during the night. Stealing a glance at the drowsy gentleman holding Danny in his ample lap, I got it.
“So he’s just an ‘old dog,’ right, Dr. Ward?”
For a second I didn’t know if she was referring to the spouse or the sausage dog. I went with the latter.
What is Cushing’s Disease?
As we say in medicine: “Age is not a disease.” I was more worried about a hormonal disease somewhat common in Dachshunds called Cushing’s Disease.
Cushing’s Disease, also known as Cushing’s Syndrome or hyperadrenocorticism (HAC), is a condition that creates excess cortisol hormone. It’s frequently diagnosed in middle-aged or older Beagles, Boston Terriers, Boxers, Dachshunds, Miniature Schnauzers and Poodles, although any breed can develop hyperadrenocorticism.
If I suspect a dog has hyperadrenocorticism, I begin with basic blood and urine tests. If the patient has increased liver enzymes (especially a very high ALP and mildly elevated ALT), high cholesterol, glucose and triglycerides, low urine specific gravity, urine glucose, proteins or evidence of infection, then Cushing’s leaps to the top of the diagnostic list.
Danny met many of these screening criteria, meaning it was time to conduct confirmatory tests. Cushing’s Syndrome is caused by either a benign tumor in the pituitary gland (an estimated 85% of cases), a malignant adrenal gland tumor (much rarer but more serious) or due to excessive steroid usage (iatrogenic HAC).
Time for Testing
There are several tests to choose from, each having unique pros and cons. The first is the Urine Cortisol/Creatinine Ratio (UCCR). This test requires the dog parent to collect two first-morning urine samples at home, usually two to three days after a potentially stressful event such as a vet visit, boarding or grooming. I use UCCR as a convenient screening test whenever a patient can’t easily make it to the clinic or if my index of suspicion is somewhat marginal.
The UCCR is very sensitive, meaning if a dog has a normal result, there’s an excellent chance it’s not Cushing’s. Unfortunately, the UCCR isn’t very specific, meaning a positive result may not be due to Cushing’s, requiring additional tests to confirm. Despite these limitations, a UCCR is an excellent starting point for initial testing, especially in at-risk breeds or those exhibiting early or mild symptoms.
The most common, and arguably preferred, assessment for Cushing’s Syndrome in dogs is the Low-Dose Dexamethasone Suppression (LDDS) test. The primary drawback to this test is it requires eight hours in the clinic, and the blood samples must be handled and prepared carefully.
In simplest terms, the patient is administered a drug, dexamethasone, to suppress adrenal function, and blood cortisol levels are measured at four and eight hours. Based on the levels and degree of elevation, a diagnosis is made. In about 70 to 80% of cases, this is the only test needed.
The ACTH-response test is another classic Cushing’s test that involves administering the hormone ACTH and measuring the resulting exaggerated cortisol stimulation. This is the gold standard test for diagnosing iatrogenic Cushing’s (i.e., caused by giving steroids) and only requires one to two hours in the clinic. Compared to LDDS, it is less sensitive and is typically reserved for special situations or as an adjunct to LDDS. Some veterinarians prefer to begin with an ACTH-response test, especially in dogs who have been prescribed certain medications, particularly steroids.
Endogenous ACTH and imaging (ultrasound, MRI, CT) are also excellent choices to diagnose or verify Cushing’s in dogs, but are more complicated and often more expensive.
In Danny’s case, we performed an LDDS test, and he was textbook positive. Because his symptoms were worsening and affecting his quality of life, not to mention the strain his 2 a.m. pee patrols and accidents were having on his family, we elected treatment.
I chose the newer trilostane (Vetoryl) over the classic mitotane (Lysodren) because I’ve found it to cause fewer side effects and is easily given once or twice daily with food. I instructed Danny’s owner to carefully monitor for any potential side effects, including vomiting, diarrhea, listlessness and not eating for 48 hours. Those signs could indicate an adverse event known as an Addisonian crisis, requiring immediate medical care.
Danny underwent follow-up ACTH-response testing at 14, 30 and 90 days to dial in his dosing. Within a couple of months, his dog mom reported a noticeable increase in energy, much less drinking and urination, weight loss (3 pounds!) and his hair was beginning to regrow.
He’d had very few medication side effects other than some inappetence and a couple of bouts of loose stool. Overall, Danny the Dachshund was more himself and less like his dog dad. That prompted an unusual query from Danny’s dog mom: “Dr. Ward, would you mind giving my husband some of Danny’s medicine?”
Cushing’s Disease, also known as Cushing’s Syndrome or hyperadrenocorticism (HAC), is a condition that creates excess cortisol hormone.
Keep a Look Out
The most common symptoms include:
- increased thirst and urination
- increased appetite and weight gain
- abdominal enlargement (pot belly)
Many dogs with Cushing’s Syndrome will also have:
- chronic skin infections
- poor hair growth resulting in thinning or bald areas, especially along the sides of the back and hips
- oily or greasy coats