REN and Hypertension: The etiology of hypertension is also complex spanning from endocrinopathies with abnormally elevated levels of one of the various pressure-controlling hormones (e.g., catecholamine, renin-angiotensin II-aldosterone axis, cortisol, and growth hormone) [3], to renal pathologies (e.g., Bartter's syndrome and Gitelman's syndrome), to primary cardiac hypertrophy, to conditions in which a clear cause-effect relationship cannot be establish (idiopathic hypertension).