Comparison of Survival Times for Dogs with Pituitary‐Dependent Hyperadrenocorticism in a Primary‐Care Hospital: Treated with Trilostane versus Untreated

BACKGROUND: Although pituitary‐dependent hyperadrenocorticism (PDH) is one of the most common endocrinopathies in dogs, the effects of withholding treatment on survival time in dogs with PDH remain unclear. HYPOTHESIS/OBJECTIVES: The purpose of this study was to clarify the effects of treatment in dogs with PDH by comparing survival times between dogs treated with trilostane and untreated dogs. ANIMALS: Forty‐three dogs diagnosed with PDH at a primary‐care hospital in Japan between June 2009 and January 2014. METHODS: Retrospective cohort study. The medical records of dogs with PDH treated with trilostane (n = 17) or left untreated (n = 26) were reviewed retrospectively. Survival analysis at 2 years after diagnosis of PDH was performed. RESULTS: Median survival time for the trilostane group was not reached (95% confidence interval [CI], 443 days–not applicable) and was significantly longer than the 506 days (95% CI, 292–564 days; P = .016) for the untreated group. Multivariate Cox proportional hazards analysis (including age at diagnosis, basal cortisol concentration at diagnosis, and treatment group) only identified assignment to the untreated group (hazard ratio, 5.01; 95% CI, 1.63–15.44) as associated with increased mortality. CONCLUSIONS AND CLINICAL IMPORTANCE: The results of this retrospective cohort study suggest that withholding treatment for dogs with PDH might be associated with a higher risk of death. This represents the largest study to date to report survival times of untreated dogs with PDH.