The ideal method to monitor trilostane therapy in dogs with hypercortisolism (HC) is still controversial. Lately, determination of the pre-trilostane (pre-pill) serum cortisol concentration has been shown to be more repeatable than either post-trilostane or post-ACTH stimulation cortisol. Therefore, the pre-pill cortisol concentration may be superior to other cortisol measurements for monitoring purposes.

As it is well known that cortisol concentrations can fluctuate and are influenced by certain circumstances (e.g., stress), the aim of this study was to investigate the agreement of two pre-pill cortisol measurements in dogs with HC during trilostane therapy.

Client owned dogs with HC treated with trilostane twice daily were prospectively enrolled. Cortisol concentrations were measured two times 1 hour apart just before the next trilostane dose (pre-pill 1 and 2). Each value was assigned to one of three groups according to the control of cortisol release: excessive (<41 nmol/l), adequate (41–138 nmol/l) or inadequate (>138 nmol/l). The Wilcoxon signed rank test was used to examine for significant differences between the paired measurements and the spearman rank correlation was calculated. The degree of agreement between group assignments was quantified by kappa.

A total of 47 cortisol pairs of 16 dogs with HC were included. Pre-pill 1 and 2 did not differ significantly (p=0.18). There was a significant correlation between the two values (p<0.0001, r=0.73). Compared to pre-pill 1, pre-pill 2 was higher in 17, equal in 5 and lower in 25 pairs. Group agreement between pre-pill 1 and 2 was 70% (moderate agreement - weighted kappa 0.5). In 30% of the pairs group assignment disagreed, which would have led to a different therapeutic decision. In some dogs, certain circumstances (e.g., excessive barking during hospitalization, difficulties during blood collection) were identified as potential factors explaining the discrepancy between pre-pill 1 and 2.

In conclusion, in a substantial number of dogs there was a large difference between the two pre-pill values, which was ascribable to certain events during hospitalization in some dogs. Recording of any incident during handling that might affect cortisol release seems important. Whether the measurement of two pre-pill values is of true benefit compared to the determination of only one has to be evaluated in further studies.

Disclosures

Disclosures to report.

NSR has been a member of the Vetoryl novel monitoring meeting 2017 organized by Dechra Veterinary Products Ltd. CR was a consultant for Boehringer Ingelheim and Novartis Animal Health and is currently a consultant for Dechra Limited. She has received financial support for her endocrine research from various companies such as Nestlé Purina, Hills, Provet, Antlia SA, Glycemicon, and from the clinical studies fund of the ECVIM-CA, and from the Society of Comparative Endocrinology.