by pain-induced sympathetic nervous system stimulation; in the early postanesthesia period, e.g. by pain-induced sympathetic stimulation, hypothermia, hypoxia, or hypervolemia from excessive intraoperative fluid therapy; and in the 24 to 48 hours after the postoperative period as fluid is mobilized from the extravascular space. In addition, hypertension may develop perioperatively because of discontinuation of long-term antihypertensive medication. Medication side effects
Certain medications, including NSAIDs (Motrin/Ibuprofen) and steroids can cause hypertension. Other medications include estrogens (such as those found in oral contraceptives with high estrogenic activity), certain antidepressants (such as venlafaxine), buspirone, carbamazepine, bromocriptine, clozapine, and cyclosporine. High blood pressure that is associated with the sudden withdrawal of various antihypertensive medications is called rebound hypertension. The increases in blood pressure may result in blood pressures greater than when the medication was initiated. Depending on the severity of the increase in blood pressure, rebound hypertension may result in a hypertensive emergency. Rebound hypertension is avoided by gradually reducing the dose (also known as "dose tapering"), thereby giving the body enough time to adjust to reduction in dose. Medications commonly associated with rebound hypertension include centrally-acting antihypertensive agents, such as clonidine and methyl-dopa.Other herbal or "natural products" which have been associated with hypertension include Ephedra, St Johns wort, and licorice. Pregnancy
Few women of childbearing age have high blood pressure, up to 11% develop hypertension of pregnancy. While generally benign, it may herald three complications of pregnancy: pre-eclampsia, HELLP syndrome and eclampsia. Follow-up and control with medication is therefore often necessary.
People with neurogenic hypertension respond poorly to treatment with diuretics as the underlying cause of their hypertension is not addressed.Pheochromocytoma – a tumor which results in an excessive secretion of norepinephrine and epinephrine which promotes vasoconstriction
Hyperaldosteronism (Conns syndrome)   – idiopathic hyperaldosteronism, liddles syndrome (also called pseudoaldosteronism), glucocorticoid remediable aldosteronism
Cushings syndrome – an excessive secretion of glucocorticoids causes the hypertension
Hyperparathyroidism
Acromegaly
Hyperthyroidism
Hypothyroidism

Adrenal
A variety of adrenal cortical abnormalities can cause hypertension, In primary aldosteronism there is a clear relationship between the aldosterone-induced sodium retention and the hypertension.Congenital adrenal hyperplasia, a group of autosomal recessive disorders of the enzymes responsible for steroid hormone production, can lead to secondary hypertension by creating atypically high levels of mineralocorticoid steroid hormones. These mineralocorticoids cross-react with the aldosterone receptor, activating it and raising blood pressure. 17 alpha-hydroxylase deficiency causes an inability to produce cortisol. Instead, extremely high levels of the precursor hormone corticosterone are produced, some of which is converted to 11-Deoxycorticosterone (DOC), a potent mineralocorticoid not normally clinically important in humans. DOC has blood-pressure raising effects similar to aldosterone, and abnormally high levels result in hypokalemic hypertension. 11β-hydroxylase deficiency, aka apparent mineralocorticoid excess syndrome, involves a defect in the gene for 11β-hydroxysteroid dehydrogenase, an enzyme that normally inactivates circulating cortisol to the less-active metabolite cortisone. At high concentrations cortisol can cross-react and activate the mineralocorticoid receptor, leading to aldosterone-like effects in the kidney, causing hypertension.