Another medical problem, usually affecting our kidneys, arteries, heart, or endocrine system, causes secondary high blood pressure. Other causes include obstructive sleep apnea, adrenal gland tumors, hormone imbalances, and excessive salt or alcohol use. During pregnancy, secondary hypertension can also be detected. Secondary hypertension, unlike initial hypertension, is easily reversible. It accounts for only 5 to 10% of all instances of hypertension and is most common in people aged 18 to 40.