Serum 17alpha-hydroxyprogesterone concentrations during the reproductive cycle in healthy dogs and dogs with hyperadrenocorticism

[Atypical Cushing's syndrome in a dog. A case report]

In a 12-year-old male Labrador Retriever, presented due to other disease symptoms, clinical signs of hyperadrenocorticism (polyuria, polydipsia, abdominal distention, muscle atrophy) were an incidental finding. Abnormal laboratory results and sonographic findings of the adrenal glands, but negative low-dose dexamethasone suppression tests with low basal cortisol concentrations, a negative andrenocorticotropic hormone (ACTH)-stimulation test and exclusion of iatrogenic hyperadrenocorticism, suggested an atypical hyperadrenocorticism (AHAC). Results of further examinations, particularly stimulation of progesterone production by ACTH (0 h value: 0.21 ng/ml; 1 h value: 4.9 ng/ml) and good response to therapy with trilostane, supported this diagnosis. However, it has to be critically considered, whether and to what extent additionally present diseases (arthroses, testicular tumour) played a role regarding the symptoms and laboratory results in this dog. This case illustrates the difficulties with the diagnosis of AHAC.

Serum cortisol concentrations in dogs with pituitary-dependent hyperadrenocorticism and atypical hyperadrenocorticism

Background

Atypical hyperadrenocorticism (AHAC) is considered when dogs have clinical signs of hypercortisolemia with normal hyperadrenocorticism screening tests.

Hypothesis/Objectives

To compare cortisol concentrations and adrenal gland size among dogs with pituitary‐dependent hyperadrenocorticism (PDH), atypical hyperadrenocorticism (AHAC), and healthy controls.

Animals

Ten healthy dogs, 7 dogs with PDH, and 8 dogs with AHAC.

Method

Dogs were prospectively enrolled between November 2011 and January 2013. Dogs were diagnosed with PDH or AHAC based on clinical signs and positive screening test results (PDH) or abnormal extended adrenal hormone panel results (AHAC). Transverse adrenal gland measurements were obtained by abdominal ultrasound. Hourly mean cortisol (9 samplings), sum of hourly cortisol measurements and adrenal gland sizes were compared among the 3 groups.

Results

Hourly (control, 1.4 ± 0.6 μg/dL; AHAC, 2.9 ± 1.3; PDH, 4.3 ± 1.5) (mean, SD) and sum (control, 11.3 ± 3.3; AHAC, 23.2 ± 7.7; PDH, 34.7 ± 9.9) cortisol concentrations differed significantly between the controls and AHAC (P < .01) and PDH (P < .01) groups. Hourly (P < .01) but not sum (P = .27) cortisol concentrations differed between AHAC and PDH dogs. Average transverse adrenal gland diameter of control dogs (5.3 ± 1.2 mm) was significantly less than dogs with PDH (6.4 ± 1.4; P = .02) and AHAC (7.2 ± 1.5; P < .01); adrenal gland diameter did not differ (P = .18) between dogs with AHAC and PDH.

Conclusions and Clinical Importance

Serum cortisol concentrations in dogs with AHAC were increased compared to controls but less than dogs with PDH, while adrenal gland diameter was similar between dogs with AHAC and PDH. These findings suggest cortisol excess could contribute to the pathophysiology of AHAC.