USE OF THE URINE CORTISOL CREATININE RATIO TO MONITOR TREATMENT RESPONSE IN DOGS WITH PITUITARY-DEPENDENT HYPERADRENOCORTICISM/

Objective-To determine the usefulness of measuring urine cortisol:crea tinine ratio (UCCR) as a means of monitoring response to mitotane trea tment in dogs with pituitary-dependent hyperadrenocorticism (PDH). Des ign-Case series. Animals-51 clinically normal dogs and 21 dogs with PD H. Procedure-The reference range for the UCCR was determined by measur ing the ratio in 51 clinically normal dogs. The usefulness of measurin g UCCR in evaluating response of 21 dogs with PDH to treatment with mi totane was evaluated by comparing ACTH-stimulated blood cortisol conce ntrations with UCCR at the end of the induction phase of treatment (13 dogs) and during the maintenance phase of treatment (21). Results-UCC R was not useful for identifying dogs with inadequate adrenal reserves at the end of the induction phase of treatment or during the maintena nce phase. The UCCR was useful for identifying dogs in which control o f cortisol secretion was not adequate. Clinical Implications-UCCR shou ld not be used for evaluation of dogs during the induction phase of tr eatment, because the potential consequences of not identifying dogs wi th inadequate adrenal reserves are great. The UCCR may be useful as an adjunct means of monitoring treatment response during the maintenance phase of treatment. However, the ACTH stimulation test remains a nece ssary component when monitoring response to treatment in dogs with PDH receiving mitotane.