Evaluating plasma renin activity as a monitoring parameter for mineralocorticoid treatment in dogs with primary hypoadrenocorticism

Abstract

Abstract Background In human medicine, plasma renin activity (PRA) is used to assess mineralocorticoid treatment adequacy in hypoadrenocorticism, with elevated levels indicating under-replacement and suppressed levels over-replacement. In dogs with primary hypoadrenocorticism, PRA is increased before treatment and decreases with treatment, but its value as a monitoring parameter remains uncertain. The objective of this study was to evaluate PRA as a marker to guide mineralocorticoid dosing in dogs with primary hypoadrenocorticism. A total of 52 PRA measurements were collected from 28 dogs during scheduled desoxycorticosterone pivalate (DOCP) treatment visits. All dogs had received DOCP and prednisolone for at least five months. PRA was measured by ELISA detecting angiotensin I. Results Median PRA was 1.6 ng/mL/h (range, 0–19.2), with 19 values above, 17 within, and 16 below the reference interval. PRA showed moderate correlations with potassium ( p = 0.009, 𝛒 = 0.36), sodium ( p = 0.02, 𝛒 = -0.33), the sodium-to-potassium (Na/K) ratio ( p = 0.006, 𝛒 = -0.38), and DOCP dose ( p = 0.02, 𝛒 = -0.34), while urine specific gravity correlated with DOCP dose ( p = 0.01, 𝛒 = -0.50). Compared with visits with decreased PRA, visits with increased PRA had a significantly lower Na/K ratio ( p = 0.048). Increased PRA occurred more frequently during visits with concurrent disease ( p = 0.005); concurrent disease was also associated with higher creatinine concentrations ( p = 0.023) and lower DOCP doses ( p = 0.004). In subgroup analyses, chronic enteropathy was associated with higher potassium concentrations ( p = 0.003), lower Na/K ratios ( p = 0.009), and higher DOCP doses ( p < 0.001), whereas chronic kidney disease was associated with higher creatinine concentrations ( p < 0.001) and lower DOCP doses ( p < 0.001). Clinical assessment and PRA status were concordant in 48% of visits. Conclusions PRA may provide additional information for monitoring mineralocorticoid treatment in dogs with hypoadrenocorticism treated with DOCP. However, its interpretation can be challenging, as it often does not match electrolyte results and both PRA and electrolytes may be affected by other diseases. Therefore, PRA should be interpreted as a supportive parameter within the clinical context.