REN and chronic kidney disease: Renin–angiotensin–aldosterone system inhibitor (RAASi) therapy, including angiotensin-converting enzyme inhibitors (ACEi), angiotensin receptor blockers (ARBs), angiotensin receptor-neprilysin inhibitors (ARNi), and steroidal and non-steroidal mineralocorticoid receptor antagonists (MRAs), is essential for treating diabetic and non-diabetic chronic kidney disease (CKD), heart failure (HF), and hypertension (HTN).