An Unexpected Cause of Severe Hypokalemia

Figure 2

Aldosterone acts primarily in the distal nephron by diffusing into the tubular cell and attaching to specific mineralocorticoid receptor (MR). After that, the ligand-receptor complex migrates into the nucleus, where it interacts with specific sites and enhances messenger RNA (mRNA) and ribosomal RNA transcription. Aldosterone-induced proteins are synthesized, such as the apical epithelial sodium channel (ENaC) and basolateral Na/K-ATPase. In vitro, aldosterone and cortisol have similar affinity to the MR. The enzyme 11β-hydroxysteroid dehydrogenase type 2 (11BHSD2) converts cortisol to inactive cortisone, preventing cortisol from binding to the MR. Glycyrrhetinic acid inhibits 11BHSD2 leading to activation of MR by cortisol.