URINARY CONCENTRATION OF CORTICOIDS IN NORMAL HORSES AND HORSES WITH HYPERADRENOCORTICISM

The urinary corticoid:creatinine (c:c) ratio was determined in eight h orses with hyperadrenocorticism (HAC). The mean (+/- SD) urinary c:c r atio of the eight horses with HAC (29 +/- 14 x 10(-6)) was significant ly (P<0.05) greater than the ratio in seven control horses (11 +/- 4.3 x 10(-6)). The urinary concentration of corticoids in control horses (201 +/- 60.4 nmol litre(-1)) was significantly (P<0.05) lower than in horses with HAC (664 +/- 291 nmol litre(-1)). The urinary creatinine concentrations did not differ significantly (P>0.05) between both grou ps. As both false negative and false positive cases were found, it is concluded that a measurement of the urinary c:c ratio in the horse sho uld not be used as the sole test to confirm equine HAC.