The aim of the present study was to investigate the use of the synthetic hormone Desmopressin for diagnosing the canine Cushing-Syndrome. It was assumed that in patients with central Cushing´s disease intravenous application of Desmopressin results in an increase of the endogenous cortisol level. Therefore an identification of canine central Cushings disease should be possible by evaluating endogenous cortisol levels after Desmopressin administration.
In 61 dogs with the tentative diagnosis of hyperadrenocorticism, Desmopressin was injected intravenously and cortisol levels were measured before and after 30, 60, and 90 minutes. Blood pressure, heart frequency and pulse quality were evaluated before and after the Desmopressin test. No negative side effects were observed. Furthermore all patients underwent standard endocrinological tests in order to obtain a diagnosis (Cushing negative, Pituitary dependent Hyperadrenocorticism - PDH, Adrenal Tumor Hyperadrenocorticism - ATH). In the case of verifying the diagnosis by follow up or pathohistological examination, data were compared with the diagnosis of the Desmopressin test and analysed statistically.
Thirty minutes after intravenous Desmopressin injection Cortisol levels were significantly different (p = 0,011) between the negative group (n=15) and the patients with Pituitary dependent Hyperadrenocorticism (n=20). Within these two groups the cortisol levels were only in the group with PDH significantly elevated (p =0,007; negative group: p = 0,940).
Desmopressin did not alter cortisol levels in patients with a functional adrenal tumor (n=4). This group was not statistically analysed on account of the small number of patients.
In this study the sensitivity and the positive predictive value of the Desmopressin test were 95%, the specifity and the negative predictive value 93 %, respectively. Therefore, the Desmopressin test is an excellent diagnostic tool for differentiating the central from of Cushing´s syndrome. It is safe, can be performed easily and at low cost and is able to provide the diagnosis of PDH within 30 minutes.