Chronic hypertension causes

Hypertension Main page
Overview
Causes
Classification Primary Hypertension Secondary Hypertension Hypertensive Emergency Hypertensive Urgency
Screening

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor-In-Chief: Taylor Palmieri

Salt sensitivity

Sodium is the environmental factor that has received the greatest attention. Approximately 60% of the essential hypertension population is responsive to sodium intake. This is due to the fact that increasing amounts of salt in a person's bloodstream causes the body to draw in more water, increasing the pressure on the blood vessel walls. In addition to sodium, choride plays an important role as it causes volume expansion increasing blood pressure as sodium with combined with other anions does not increase blood pressure. Also salt sensitivity is known to be increased with increasing age, obesity, in African americans and in the metabolic syndrome.

Mechanisms

The proposed mechanism for salt-sensitvity is incraesed salt intake over a long period of time leads to impaired excretion of salt which causes hypertension. There may be several other pathways involved in the pathophysiology of salt-sensitivity leading to hypertension. Salt-sensitive patients are known to have a dysregulated renin-angiotensin pathway and patients show an abnormal vascular response to angiotensin II. Increased sodium re absorption, though not well understood, is mostly related abnormalities across Na-H proximal tubule channels, Na-K-Cl co-transporter across the thick ascending limb, Na-Cl distal tubule co-transporter and epithelial Na channels. Dietary deficiency in potassium is also known to trigger increased sodium sensitivity in patients in particular African-Americans, but the mechanism is still not clearly determined.

Role of renin

Renin is a hormone secreted by the juxtaglomerular cells of the kidney and linked with aldosterone in a negative feedback loop. The range of renin activity observed in hypertensive subjects tends to be broader than in normotensive individuals. In consequence, some hypertensive patients have been defined as having low-renin and others as having essential hypertension. Low-renin hypertension is more common in African Americans than Caucasians and may explain why they tend to respond better to diuretic therapy than drugs that interfere with the renin-angiotensin system.

High Renin levels predispose to Hypertension: Increased Renin --> Increased Angiotensin II --> Increased Vasoconstriction, Thirst/ADH and Aldosterone --> Increased Sodium Reabsorption in the Kidneys (DCT and CD) --> Increased Blood Pressure.

Insulin resistance

Insulin is a polypeptide hormone secreted by the pancreas. Its main purpose is to regulate the levels of glucose in the body antagonistically with glucagon through negative feedback loops. Insulin also exhibits vasodilatory properties. In normotensive individuals, insulin may stimulate sympathetic activity without elevating mean arterial pressure. However, in more extreme conditions such as that of the metabolic syndrome, the increased sympathetic neural activity may over-ride the vasodilatory effects of insulin. Insulin resistance and/or hyperinsulinemia have been suggested as being responsible for the increased arterial pressure in some patients with hypertension. This feature is now widely recognized as part of syndrome X, or the metabolic syndrome.

Sleep apnea

Sleep apnea is a common, under-recognized cause of hypertension. It is best treated with UPPP, tonsilectomy, adenoidectomy, sinus surgery, or weight loss, nocturnal nasal positive airway pressure, or the Mandibular advancement splint (MAS).

Genetics

Hypertension is one of the most common complex disorders, with genetic heritability averaging 30%. Data supporting this view emerge from animal studies as well as in population studies in humans. Most of these studies support the concept that the inheritance is probably multifactorial or that a number of different genetic defects each have an elevated blood pressure as one of their phenotypic expressions.

More than 50 genes have been examined in association studies with hypertension, and the number is constantly growing.

Causes of Secondary Hypertension

Only in a small minority of patients with elevated arterial pressure, can a specific cause be identified. These individuals will probably have an endocrine or renal defect that, if corrected, could bring blood pressure back to normal values. Common causes include:

Renal hypertension

Hypertension produced by diseases of the kidney. This includes diseases such as polycystic kidney disease or chronic glomerulonephritis. Hypertension can also be produced by diseases of the renal arteries supplying the kidney. This is known as renovascular hypertension; it is thought that decreased perfusion of renal tissue due to stenosis of a main or branch renal artery activates the renin-angiotensin system.

Adrenal hypertension

Hypertension is a feature of a variety of adrenal cortical abnormalities. In primary aldosteronism there is a clear relationship between the aldosterone-induced sodium retention and the hypertension.

In patients with pheochromocytoma increased secretion of catecholamines such as epinephrine and norepinephrine by a tumor (most often located in the adrenal medulla) causes excessive stimulation of [adrenergic receptors], which results in peripheral vasoconstriction and cardiac stimulation. This diagnosis is confirmed by demonstrating increased urinary excretion of epinephrine and norepinephrine and/or their metabolites (vanillylmandelic acid).

Diet

The North American diet that is high in fat and salt has been proven to exacerbate hypertension. A study in the U.S. found that patients placed on a strict vegetarian diet showed a significant benefit to their condition over the one year. Certain medications, especially NSAIDS (Motrin/ibuprofen) and steroids can cause hypertension. Imported licorice (Glycyrrhiza glabra) inhibits the 11-hydroxysteroid hydrogenase enzyme (catalyzes the reaction of cortisol to cortison) which allows cortisol to stimulate the Mineralocorticoid Receptor (MR) which will lead to effects similar to hyperaldosteronism, which itself is a cause of hypertension.

Age

Over time, the number of collagen fibers in artery and arteriole walls increases, making blood vessels stiffer. With the reduced elasticity comes a smaller cross-sectional area in systole, and so a raised mean arterial blood pressure.

Complete List of Secondary Causes of Hypertension

(By organ system)

Cardiovascular	Aortic regurgitation, Aortic dissection, Acute severe vascular damage, Adams Nance syndrome , Aneurysm, Aortic coarctation , Aortic stenosis, Arterial occlusive disease, progressive - -- heart defects -- bone fragility -- brachysyndactyly , Arteriosclerosis, Atheroma, Avasthey syndrome , Carotid Paraganglioma , Congenital mitral stenosis , Eisenmenger's Syndrome , Fibromuscular dysplasia of arteries , Grange syndrome , Hemangiomatosis - familial pulmonary capillary, Hypertensive heart disease , Pulmonary artery agenesis , Vasculitis , Patent ductus arteriosus, Third degree AV block
Chemical / poisoning	Acetaldehyde , Aristolochic acid poisoning , Arizona Bark Scorpion poisoning , Black widow spider envenomation , Cadmium poisoning, Cocaine poisoning , Ecstasy abuse , Ginseng , Heavy metal poisoning, Indian Tobacco poisoning, Jimsonweed poisoning , Lead poisoning , Lockwood-Feingold syndrome , Mustard tree poisoning , Nicotine addiction , Pseudoephedrine poisoning , Silicosis , Toxic mushrooms -- Psychedelic
Dermatologic	No underlying causes
Drug Side Effect	Almotriptan, Dihydroergotamine, Ergotamine, Frovatriptan, Isometheptene, Rizatriptan, Sumatriptan, Zolmitriptan, Amitriptyline, Cyclosporine, Desipramine, Dexamethasone sensitive hypertension , Doxepin, Ephedrine poisoning, Glucocorticoid resistance , Imipramine, Nasal decongestants, Nortriptyline, Combined oral contraceptive pill, Phencyclidine, Phenylpropanolamine, Protriptyline, Sedative dependence, Serotonin toxicity, Steroid abuse
Ear Nose Throat	No underlying causes
Endocrine	Carcinoid Syndrome, Acromegaly , Adrenal incidentaloma , Alcohol-induced pseudo-Cushing syndrome , Angiotensin/rennin/aldosterone hypertension , Apparent mineralocorticoid excess , Congenital adrenal hyperplasia - 11-Beta-hydroxylase deficiency, Congenital adrenal hyperplasia - 17-alpha-hydroxylase deficiency, Conn's syndrome, Cushing's disease, Cushing's syndrome , Diabetes, Familial Cushing syndrome , Graves Disease , Hyperadrenalism , Hyperparathyroidism , Hyperpituitarism , Hyperthyroidism, Hypothyroidism,Isolated secretion of corticosterone, Isolated secretion of deoxycorticosterone, Lobelia poisoning , Mineralocorticoid excess, Multiple endocrine neoplasia type 1, Myxoedema, Pheochromocytoma, Primary aldosteronism, Primary cortisol resistance, Pseudohyperaldosteronism , Pseudohypoaldosteronism , Schroeder syndrome 1 , Hyperthyroidism, Hypoglycemia
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	No underlying causes
Hematologic	No underlying causes
Iatrogenic	No underlying causes
Infectious Disease	No underlying causes
Musculoskeletal / Ortho	No underlying causes
Neurologic	Guillain-Barre Syndrome, Autonomic dysreflexia syndrome , Binswanger's Disease , Brain stem encephalitis, Central sleep apnea , Choroideremia -- hypopituitarism , Disequilibrium syndrome , Dysautonomia , Hereditary sensory and autonomic neuropathy 3 , Increased intracranial pressure, Neurofibromatosis syndrome Type II , Neurogenic hypertension , Nipah virus encephalitis , Obstructive sleep apnea , Sneddon Syndrome , Upper spinal cord lesions, Wolfram's disease, Meningitis, Polyradiculitis, Quadriplegia
Nutritional / Metabolic	No underlying causes
Obstetric/Gynecologic	No underlying causes
Oncologic	No underlying causes
Opthalmologic	No underlying causes
Overdose / Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	No underlying causes
Renal / Electrolyte	No underlying causes
Rheum / Immune / Allergy	No underlying causes
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Dental	No underlying causes
Miscellaneous	No underlying causes