Use of urine cortisol:creatinine ratio versus adrenocorticotropic hormone stimulation testing for monitoring mitotane treatment of pituitary-dependent hyperadrenocorticism in dogs.
OBJECTIVE
To evaluate use of urine cortisol-to-creatinine ratio (UC:C) as a means of monitoring response to long-term mitotane treatment in dogs with pituitary-dependent hyperadrenocorticism.


METHODS
Prospective uncontrolled study.


METHODS
101 dogs with pituitary-dependent hyperadrenocorticism.


METHODS
Urine samples were obtained from dogs on the morning an ACTH stimulation test was performed, and owners were asked their opinion on the health of their dog to monitor response to mitotane treatment. Urine was assayed for cortisol and creatinine concentrations, and UC:C was calculated. The UC:C was compared with post-ACTH plasma cortisol concentration.


RESULTS
Post-ACTH plasma cortisol concentration was used to categorize each dog's response to mitotane treatment. The UC:C did not correlate satisfactorily with results of ACTH stimulation testing. Twenty-seven of 85 (32%) dogs would have been incorrectly considered as having received appropriate doses using UC:C. In addition, 16 dogs that received overdoses could not be distinguished from 29 dogs that received appropriate doses.


CONCLUSIONS
UC:C does not provide a consistent, correct assessment of mitotane-induced adrenocortical destruction. The ACTH stimulation test, although more time-consuming and expensive, is recommended for monitoring response to mitotane treatment.
Angles
J M
JM
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616-8734, USA.
Feldman
E C
EC
Nelson
R W
RW
Feldman
M S
MS
D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D000308:Adrenocortical Hyperfunction / Q000188:drug therapy / Q000378:metabolism / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D003404:Creatinine / Q000097:blood / Q000652:urine*; D003907:Dexamethasone / Q000494:pharmacology; D004283:Dog Diseases / Q000097:blood / Q000188:drug therapy* / Q000652:urine; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006854:Hydrocortisone / Q000097:blood / Q000652:urine*; D008939:Mitotane / Q000627:therapeutic use*; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology; D011446:Prospective Studies; D015203:Reproducibility of Results
D000970:Antineoplastic Agents; D008939:Mitotane; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003404:Creatinine; D006854:Hydrocortisone