REN and chronic kidney disease: Drugs that inhibit the renin–angiotensin–aldosterone system (RAAS inhibitors), such as angiotensin-converting enzyme inhibitors (ACEi), angiotensin-II receptor blockers (ARB) and mineralocorticoid receptor antagonists (MRA), reduce the morbidity and mortality of hypertension [1], congestive heart failure (CHF) with reduced ejection fraction [2] and reduce proteinuria and slow the decline of estimated glomerular filtration rate (eGFR) in chronic kidney disease (CKD) [3].