Using baseline cortisol to monitor twice-daily trilostane in dogs

Abstract

OBJECTIVE: To evaluate use of cortisol concentration prior to ACTH stimulation (baseline) to monitor efficacy of twice-daily administration of trilostane to dogs with pituitary-dependent hyperadrenocorticism (PDH). DESIGN: Retrospective case series. ANIMALS: 22 dogs with PDH. PROCEDURES: The database of a veterinary hospital was searched to identify dogs with PDH that were treated with the FDA-approved veterinary formulation of trilostane twice daily between January 1, 2008, and December 31, 2012. For each dog, signalment and details regarding each hospital visit including comorbidities, electrolyte concentrations, and clinical signs were extracted from the record. For each ACTH stimulation test performed, the respective correlations between baseline cortisol concentration and the cortisol concentration after ACTH stimulation (ACTH-stimulated cortisol concentration) and resultant decision regarding trilostane dose adjustment were determined. Excessive suppression of cortisol production was defined as an ACTH-stimulated cortisol concentration < 2.0 &#x3bc;g/dL. The ability of various baseline cortisol concentrations to predict whether a dog had excessive suppression of cortisol production was determined. RESULTS: 109 ACTH stimulation tests were performed for the 22 dogs. A baseline cortisol concentration > 3.2 &#x3bc;g/dL predicted that ACTH-stimulated cortisol concentration would be &#x2265; 2.0 &#x3bc;g/dL with 100% certainty; however, 14 of 64 tests with a baseline cortisol concentration > 3.2 &#x3bc;g/dL had an ACTH-stimulated cortisol concentration &#x2264; 3.2 &#x3bc;g/dL, which was suggestive of inadequate adrenocortical cortisol reserves. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that baseline cortisol concentration should not be used as the sole monitoring tool for management of dogs with PDH treated with trilostane twice daily.