Hot Literature: Is there a simpler way to monitor adrenal function in patients receiving trilostane?

Many dogs receive trilostane as a treatment for hyperadrenocorticism. Periodic monitoring of adrenal gland function is necessary in patients receiving this medication to ensure adequate control of serum cortisol. An ACTH stimulation test is the gold standard for monitoring these patients, but performing this test requires admission to the clinic, two venipunctures, and added expense to the client.

This inconvenience to owners and animals can result in poor client compliance, putting dogs at risk for complications associated with poorly controlled adrenal gland function. To address these concerns, researchers at Texas A&M University's Department of Small Animal Clinical Sciences conducted a study looking at the accuracy of a single cortisol concentration measurement to monitor dogs receiving trilostane for hyperadrenocorticism.

This controlled drug efficacy study involved 103 client-owned dogs and was designed to identify a correlation between baseline cortisol concentrations and the results of ACTH stimulation tests. ACTH stimulation tests and baseline cortisol concentration measurements were performed before treatment and again every two weeks for 12 weeks after starting trilostane. The tests were conducted four to six hours after the morning dosing of trilostane, and definitions of excessive suppression, inadequate control, and acceptable control were based on ACTH stimulation results suggested by trilostane's manufacturer.

Based on the ACTH stimulation test guidelines, the two monitoring methods were compared. The evaluation of the paired tests demonstrated that baseline serum cortisol concentrations of 1.3 to 2.9 µg/dl corresponded to adequate control of adrenal gland function based on the matching ACTH test results. Furthermore, those baseline concentrations falling above or below these levels accurately excluded either excessive suppression or inadequate control.

These results indicate that, while being treated with trilostane, dogs may be screened for adequate adrenal control with a single serum cortisol concentration. However, the researchers caution that it is critical to weigh information regarding a patient's overall health when making dosing decisions and that when more precise information regarding adrenal function is needed, ACTH stimulation testing is necessary. However, these results do suggest that in dogs free of any signs indicating poor control while receiving trilostane, a baseline serum cortisol concentration can be useful as a screening tool. While further investigation including additional variables should be conducted, the study results suggest that simplifying monitoring in these patients is possible with a goal of improved client compliance and overall patient care.

Cook AK, Bond KG. Evaluation of the use of baseline cortisol concentration as a monitoring tool for dogs receiving trilostane as a treatment for hyperadrenocorticism. J Am Vet Med Assoc 2010;237(7):801-805.

Link to abstract: http://avmajournals.avma.org/doi/abs/10.2460/javma.237.7.801