01.03.2016 | Original Article | Ausgabe 2/2016
Duration of blood plasma cortisol suppression after a low-dose dexamethasone suppression test in dogs
Comparative Clinical Pathology
- Stefanie Hoffrogge, Marion Schmicke, Reinhard Mischke
The aim of this study was to determine the duration of the suppressive effect on the hypothalamus–pituitary–adrenocortical axis as measured by plasma cortisol concentration after injection of a low dosage of dexamethasone (0.01 mg/kg BW) used within the low-dose dexamethasone suppression test (LDDST). A LDDST was performed on ten clinically healthy dogs with unremarkable haematological and plasma biochemical profiles, abdominal X-ray, abdominal ultrasonography and fine needle aspiration cytology of the liver. Two of them were excluded from the analysis. Blood samples were collected at baseline, 4 and 8 h (standard protocol of a LDDST) and, additionally, at 24, 48, 72 and 96 h after the application of dexamethasone. Plasma cortisol concentrations <10 ng/ml were considered as suppressed. All eight dogs had suppressed plasma cortisol levels after 4 and 8 h. Three dogs still had suppressed plasma cortisol levels at 24 h after dexamethasone application, and one of them even had a suppressed level after 48 h. After 72 h, all dogs had plasma cortisol levels >10 ng/ml. The median 4, 8 and 24 h plasma cortisol concentrations were significantly lower than the median baseline plasma cortisol concentration, whereas at the remaining times no significant changes were seen compared to the median baseline value. The suppression of plasma cortisol induced by dexamethasone in a dosage of 0.01 mg/kg BW can last at least 48 h in individual dogs. Therefore, a repeated LDDST should be performed at the earliest 3 days after the prior test to prevent artificial results.