Corticotropin-Releasing Hormone Test to Differentiate Hyperadrenocorticism in Dogs
Thomas Schermerhorn, VMD, DACVIM (SAIM), Kansas State University
In the Literature
Tanaka S, Suzuki S, Sato A, et al. Utility of a corticotropin-releasing hormone test to differentiate pituitary-dependent hyperadrenocorticism from cortisol-producing adrenal tumors in dogs. J Vet Intern Med. 2022;36(1):29-38. doi:10.1111/jvim.16336
The Research ...
Corticotropin-releasing hormone is produced in the hypothalamus and is a component of the hypothalamic–pituitary–adrenal axis. This hormone stimulates the release of ACTH from the pituitary gland, targeting the adrenal cortex and stimulating a hormonal response that includes release of cortisol and related glucocorticoid hormones. Although some tests (eg, ACTH stimulation, dexamethasone suppression) that evaluate the hypothalamic–pituitary–adrenal axis may be familiar, others (eg, corticotropin-releasing hormone test) are infrequently used in the clinical setting.
This study evaluated the usefulness of a corticotropin-releasing hormone test for distinguishing pituitary-dependent hyperadrenocorticism (PDH) from hyperadrenocorticism caused by a cortisol-producing adrenal tumor (ie, adrenal-dependent hyperadrenocorticism [ADH]). Plasma ACTH was measured before and 30 minutes after IV injection of 1.5 µg ovine corticotropin-releasing factor.
Postinjection values increased significantly from baseline in all study groups (ie, control, PDH, ADH), demonstrating that ovine corticotropin-releasing hormone stimulated ACTH release. Baseline and postinjection ACTH were higher in the PDH group compared with the control and ADH groups. There was no difference in postinjection concentrations between the control and ADH groups.
Baseline and postinjection ACTH had moderate sensitivity (83.87%) and high specificity (96.97%) to distinguish between dogs in the PDH and control groups. Baseline ACTH had moderate sensitivity (90.62%) and specificity (87.50%) and postinjection ACTH had high sensitivity (100%) and moderate to low specificity (66.67%) to distinguish between dogs in the PDH and ADH groups.
... The Takeaways
Key pearls to put into practice:
The corticotropin-releasing hormone test is not appropriate for initial diagnosis of hyperadrenocorticism in dogs. Diagnosis in dogs with appropriate clinical signs requires one or more clinically useful screening tests (eg, low-dose dexamethasone suppression, ACTH stimulation).
Common tests to differentiate PDH from ADH include high-dose dexamethasone suppression, endogenous ACTH concentration, and adrenal imaging. The corticotropin-releasing hormone test is clinically useful and an alternative differentiation test option. Overall sensitivity and specificity of the corticotropin-releasing hormone test are comparable with other differentiation tests.
Time needed for the corticotropin-releasing hormone test (ie, 30 minutes) is comparable to that needed for adrenal ultrasonographic examination and is significantly shorter than the 8-hour period required for the high-dose dexamethasone suppression test.
Lack of familiarity and experience with corticotropin-releasing hormone preparations and incomplete details regarding cost of testing may inhibit use. Further studies are needed before the corticotropin-releasing hormone test can be recommended for routine clinical practice.
Test performance, cost, logistics (eg, sampling times, availability of reagents and equipment), and convenience for the pet owner and veterinary staff should be considered when selecting a test to differentiate PDH from ADH.
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