Use of plasma renin activity to monitor mineralocorticoid treatment in dogs with primary hypoadrenocorticism: desoxycorticosterone versus fludrocortisone

Abstract

Background: Measurement of plasma renin activity (PRA) is the gold standard for monitoring mineralocorticoid treatment in humans with primary hypoadrenocorticism (PH).

Objectives: To compare PRA in dogs with newly diagnosed PH, dogs with diseases mimicking PH, and healthy dogs, and evaluate measurement of PRA to monitor therapeutic effects in dogs with PH treated with different mineralocorticoids.

Animals: Eleven dogs with newly diagnosed PH (group 1), 10 dogs with diseases mimicking PH (group 2), 21 healthy dogs (group 3), 17 dogs with treated PH (group 4).

Methods: In group 1, PRA was measured before treatment and at different times after initiating treatment. In groups 2 and 3, PRA was measured at initial presentation only. In group 4, no baseline PRA was obtained but PRA was measured once or every 1-6 months during treatment. Mineralocorticoid treatment consisted of fludrocortisone acetate (FC) or desoxycorticosterone pivalate (DOCP).

Results: Plasma renin activity before treatment was increased in dogs with PH compared to normal dogs and dogs with diseases mimicking PH with median activity of 27, 0.8, and 1.0 ng/mL/h, respectively. In dogs with PH, PRA decreased and normalized with mineralocorticoid treatment using DOCP but not with FC. In dogs treated with DOCP, PRA was lower than in dogs treated with FC. Plasma sodium concentrations were higher and potassium concentrations were lower with DOCP treatment compared to FC treatment.

Conclusion and clinical importance: Plasma renin activity is a reliable tool for monitoring mineralocorticoid treatment. DOCP treatment more effectively suppresses PRA compared to FC in dogs with PH.

Keywords: Adrenal insufficiency; Canine; Hormone replacement; Therapy.

Figure 1

Plasma renin activity (PRA) of dogs with primary hypoadrenocorticism (PH, n = 11), dogs with diseases mimicking PH (n = 10), and healthy dogs (n = 21). The horizontal bars represent the medians of each group.

Figure 2

(A) Plasma renin activity (PRA) of dogs with primary hypoadrenocorticism (PH) treated with fludrocortisone acetate (FC, open circles) or with desoxycorticosterone pivalate (DOCP, closed circles). Three dogs were lost to follow‐up (triangles). (B) Bar graphs showing mean (SD) PRA of dogs with PH treated with FC (white bars) and DOCP (black bars).

Figure 3

Plasma renin activity (PRA) of dogs with primary hypoadrenocorticism on fludrocortisone acetate treatment (FC, n = 19) and on desoxycorticosterone pivalate treatment (DOCP, n = 11). The horizontal bars represent the medians.

Figure 4

Serum sodium (A) and potassium (B) concentrations of dogs with primary hypoadrenocorticism on fludrocortisone acetate treatment (FC, n = 19) and on desoxycorticosterone pivalate treatment (DOCP, n = 11). The horizontal bars represent the medians.

Figure 5

Effects of switching hormone replacement treatment in 4 dogs with primary hypoadrenocorticism (square, triangle, rhombus, and circle) from fludrocortisone acetate (FC, open symbols) to desoxycorticosterone pivalate (DOCP, closed symbols). Plasma renin activity (A), serum sodium concentrations (B), and serum potassium concentrations (C): All normalize after switching from initial FC to final DOCP treatment. The dotted lines in figures A and C represent the upper limit of normal values. The dotted line in figure B represents the lower limit of normal values.