Evaluation of clinical, ultrasonographic, and clinicopathological findings in dogs with pituitary-dependent hypercortisolism and poor trilostane response.

BACKGROUND

Trilostane is the treatment of choice for pituitary-dependent hypercortisolism (PDH) in dogs, but predictors of a poor response are unclear.

HYPOTHESIS/

OBJECTIVES

To identify variables associated with a poor response to trilostane in dogs with PDH.

ANIMALS: Twenty-three dogs with PDH treated with trilostane.

METHODS

Retrospective cohort study. Clinical, clinicopathological, endocrine, ultrasonographic, and treatment data were reviewed. Dogs were classified as good responders (GRs) or nonresponders (NRs) based on clinical outcomes after 4-8 months of trilostane treatment. The primary outcome was treatment response.

RESULTS

Fifteen dogs were GRs and 8 were NRs. At diagnosis, GRs had lower alanine aminotransferase (ALT) (median [IQR] 182 [70-251] vs 330 [224-578] U/L; P = .004), eACTH (14.4 [9.25-29.13] vs 49.2 [34.35-62.35] pg/mL; P = .007), and pre-ACTH cortisol (4.28 [3.07-6.52] vs 9.0 [6.57-19.40] μg/dL; P = .019) than NRs. Bilateral adrenomegaly was more frequent in NRs (8/8) than in GRs (9/15; P = .007). At T1, NRs required more rechecks (median [IQR] 7 [6-7] vs 3 [3-5]; P < .001) and higher trilostane doses (3.25 [3-5.75] vs 1.22 [0.66-1.60] mg/kg q12h; P < .001). After false discovery rate adjustment, ALT, eACTH, alopecia, and bilateral adrenomegaly remained significant (q = 0.047 for each). All GRs achieved complete clinical resolution within 4 months of treatment initiation.

CONCLUSIONS AND CLINICAL

IMPORTANCE

Higher baseline ALT, eACTH, and pre-ACTH cortisol, as well as bilateral adrenomegaly, were associated with a poor response to trilostane. A lack of improvement by 4-8 months and the need for higher doses or more rechecks supports early therapeutic reassessment.