Most dogs treated with trilostane for Cushing’s disease live about 1.5 to 2.5 years after diagnosis, though some live significantly longer. The median survival time in referral settings ranges from 662 to 900 days (roughly 22 to 30 months) for dogs with the most common form of the disease. Real-world numbers from primary care practices tend to be a bit lower, closer to 521 days (about 17 months), reflecting the wider mix of cases and conditions veterinarians see day to day.
Survival Times by Type of Cushing’s Disease
The type of Cushing’s disease your dog has is one of the biggest factors in how long trilostane treatment can sustain a good quality of life. About 80 to 85% of dogs with Cushing’s have the pituitary-dependent form (PDH), caused by a small tumor on the pituitary gland in the brain. The remaining cases are adrenal-dependent (ADH), caused by a tumor on one of the adrenal glands themselves.
Dogs with pituitary-dependent Cushing’s generally do better on trilostane. Published survival times for these dogs range from 549 to 930 days, which works out to roughly 18 months to 2.5 years. Dogs with adrenal tumors have shorter median survival times on trilostane, typically between 353 and 475 days (about 12 to 16 months). One study found a median of 14 months for adrenal tumor dogs on trilostane, which was statistically no different from those treated with the older drug mitotane (15.6 months). Because trilostane causes fewer and milder side effects, it’s often preferred as the first-line medical option when surgery isn’t feasible.
What Affects How Long Your Dog Will Live
Age at diagnosis is consistently the strongest predictor of survival. Dogs diagnosed later in life simply have less remaining lifespan regardless of treatment, so a dog diagnosed at age 8 will, on average, outlive one diagnosed at 12. This isn’t specific to Cushing’s or trilostane; it reflects the natural reality of aging.
Beyond age, several other factors are linked to shorter survival:
- Calcinosis cutis: hard, calcium-like deposits in the skin. Dogs with this condition at the time of diagnosis had roughly five times the risk of dying sooner in one study.
- Low body condition: dogs that were underweight (a body condition score of 3 out of 9 or lower) had about eight times the risk of earlier death.
- Higher weight at diagnosis and elevated blood phosphate levels have also been associated with poorer outcomes.
These factors don’t seal a dog’s fate. They’re statistical tendencies across large groups. Individual dogs with one or more of these risk factors can still respond well to treatment and live comfortably for years.
How Quickly Symptoms Improve
One of the most encouraging aspects of trilostane is how quickly it can improve your dog’s daily life. When given twice daily, many dogs show resolution of core symptoms like excessive thirst, frequent urination, increased appetite, and lethargy within 9 to 12 days. On a once-daily schedule, these improvements typically take closer to three months.
Skin and coat problems are slower to resolve. Hair regrowth, thinning skin, and other dermatological signs often take about six months to noticeably improve. So if your dog still looks rough-coated a month or two into treatment, that’s expected.
Monitoring That Keeps Treatment on Track
Trilostane works by temporarily blocking cortisol production, not by destroying adrenal tissue. That means the dose needs regular fine-tuning. The standard monitoring schedule calls for a hormone stimulation test at 10 to 14 days after starting the medication, then again at 30 days, 90 days, and every three months after that. Any time the dose is adjusted, the clock resets with another test at 10 to 14 days.
These tests measure how much cortisol the adrenal glands produce when stimulated. If the levels come back too low, the dose gets reduced before your dog develops signs of cortisol deficiency. If levels are still too high, the dose goes up. This ongoing calibration is a major part of why regular vet visits matter so much for dogs on trilostane. Skipping monitoring increases the risk of either under-treating the Cushing’s or overcorrecting into dangerous territory.
The Main Risk: Too Little Cortisol
The most significant side effect of trilostane is pushing cortisol levels too far in the other direction, a condition called iatrogenic hypoadrenocorticism (essentially, drug-induced Addison’s disease). In a study of 156 dogs, about 15% developed this complication within the first two years of treatment, and 26% by 4.3 years.
The reassuring part: three-quarters of these episodes were transient. The adrenal glands recovered once the trilostane dose was reduced or temporarily stopped. Permanent adrenal damage is possible but much less common. Signs to watch for include sudden lethargy, vomiting, diarrhea, loss of appetite, or collapse. These warrant immediate veterinary attention because cortisol deficiency can become life-threatening quickly.
What These Numbers Mean for Your Dog
Median survival times are the point where half the dogs in a study have died and half are still alive. That means a substantial number of dogs live well beyond the median. A dog diagnosed at age 9 with pituitary-dependent Cushing’s, started promptly on trilostane, and monitored consistently could realistically live to 12 or older. Some dogs in published studies survived over 1,000 days.
Without treatment, outcomes are grimmer. In one large study, untreated dogs had a median survival of just 178 days, compared to 521 days for those on trilostane. While that comparison didn’t reach statistical significance due to the small number of untreated dogs (only 18), the trend is consistent with what veterinarians observe in practice: Cushing’s disease, left unchecked, drives a cascade of complications including high blood pressure, blood clots, infections, and organ damage that shorten life considerably.
Trilostane doesn’t cure Cushing’s disease. It manages cortisol levels well enough that many dogs return to something close to their normal selves, drinking normal amounts of water, sleeping through the night without needing to go out, and regaining muscle tone and energy. How long that quality of life lasts depends on the type of Cushing’s, your dog’s age and overall health, and how consistently the medication is monitored and adjusted.