Evaluation of the use of baseline cortisol concentration as a monitoring tool for dogs receiving trilostane as a treatment for hyperadrenocorticism

Abstract

To determine whether a single measurement of cortisol concentration can be used to monitor dogs receiving trilostane for hyperadrenocorticism. Controlled drug efficacy trial. 103 client-owned dogs. Results of ACTH stimulation tests before and during trilostane treatment were evaluated. Each cortisol concentration after ACTH stimulation was classified as indicative of excessive, acceptable, or inadequate control of adrenal gland function, as outlined by the trilostane manufacturer. Baseline cortisol concentrations before and during trilostane treatment were evaluated; target variables were defined, and sensitivity, specificity, and predictive values were determined. Results of 103 and 342 ACTH stimulation tests before and during treatment were evaluated. In this population, baseline cortisol concentrations ≥ 1.3 µg/dL accurately excluded excessive suppression (defined by cortisol concentration after ACTH stimulation < 1.5 µg/dL) in 254 of 259 (98%) dogs. In addition, baseline cortisol concentrations ≤ 2.9 µg/dL correctly excluded inadequate control (defined by cortisol concentration after ACTH stimulation > 9.1 µg/dL) in 200 of 211 (95%) dogs. During trilostane treatment, baseline cortisol concentrations between 1.3 and either 2.9 µg/dL or ≤ 50% of the pretreatment baseline cortisol concentration correctly predicted acceptable control of adrenal gland function in 147 of 168 (88%) dogs. Evaluation of a baseline cortisol concentration collected 4 to 6 hours after trilostane administration in dogs with hyperadrenocorticism provided clinically useful information about control of adrenal gland function. Many dogs receiving trilostane may be adequately monitored without the expense and inconvenience of an ACTH stimulation test.