Use of Plasma Renin Activity to Monitor Mineralocorticoid Treatment in Dogs with Primary Hypoadrenocorticism: Desoxycorticosterone Versus Fludrocortisone

BackgroundMeasurement of plasma renin activity (PRA) is the gold standard for monitoring mineralocorticoid treatment in humans with primary hypoadrenocorticism (PH).ObjectivesTo comparePRAin dogs with newly diagnosedPH, dogs with diseases mimickingPH, and healthy dogs, and evaluate measurement ofPRAto monitor therapeutic effects in dogs withPHtreated with different mineralocorticoids.AnimalsEleven dogs with newly diagnosedPH(group 1), 10 dogs with diseases mimickingPH(group 2), 21 healthy dogs (group 3), 17 dogs with treatedPH(group 4).MethodsIn group 1,PRAwas measured before treatment and at different times after initiating treatment. In groups 2 and 3,PRAwas measured at initial presentation only. In group 4, no baselinePRAwas obtained butPRAwas measured once or every 1–6 months during treatment. Mineralocorticoid treatment consisted of fludrocortisone acetate (FC) or desoxycorticosterone pivalate (DOCP).ResultsPlasma renin activity before treatment was increased in dogs withPHcompared to normal dogs and dogs with diseases mimickingPHwith median activity of 27, 0.8, and 1.0 ng/mL/h, respectively. In dogs withPH,PRAdecreased and normalized with mineralocorticoid treatment usingDOCPbut not withFC. In dogs treated withDOCP,PRAwas lower than in dogs treated withFC. Plasma sodium concentrations were higher and potassium concentrations were lower withDOCPtreatment compared toFCtreatment.Conclusion and Clinical ImportancePlasma renin activity is a reliable tool for monitoring mineralocorticoid treatment.DOCPtreatment more effectively suppressesPRAcompared toFCin dogs withPH.