Secondary hypertension is a type of hypertension which by definition is
caused by an identifiable underlying secondary cause. It is much less common
than the other type, called essential hypertension, affecting only 5% of
hypertensive patients. It has many different causes including endocrine
diseases, kidney diseases, and tumors. It also can be a side effect of many
medications. Types
= Renovascular hypertension = It has two main causes: fibromuscular
dysplasia and atheromatous stenosis. Also diabetes
See main article at Renovascular hypertension.
= Hypertension secondary to other renal disorders =
Chronic renal failure Kidney disease / renal artery stenosis:
the normal physiological response to low blood pressure in the renal arteries is
to increase cardiac output to maintain the pressure needed for glomerular
filtration. Here, however, increased CO cannot solve the structural problems
causing renal artery hypotension, with the result that CO remains chronically
elevated. Renal segmental hypoplasia
= Hypertension secondary to endocrine disorders =
Neurogenic hypertension - excessive secretion of norepinephrine and
epinephrine which promotes vasoconstriction resulting from chronic
high activity of the sympathoadrenal system, the sympathetic nervous system
and the adrenal gland. The specific mechanism involved is increased release
of the "stress hormones", epinephrine and norepinephrine which increase blood
output from the heart and constrict arteries. 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 - idiopathic
hyperaldosteronism, liddle's syndrome, glucocorticoid remediable aldosteronism
Cushing's syndrome - an excessive secretion of glucocorticoids causes the
hypertension Hyperparathyroidism
Acromegaly Hyperthyroidism
Hypothyroidism = Other secondary hypertension =
Hormonal contraceptives Neurologic disorders
Obstructive sleep apnea Liquorice
Scleroderma Neurofibromatosis
Pregnancy: unclear etiology. Cancers: tumours in the kidney can
operate in the same way as kidney disease. More commonly, however, tumors
cause inessential hypertension by ectopic secretion of hormones involved
in normal physiological control of blood pressure.
Drugs: In particular, alcohol, nasal decongestants with adrenergic effects,
NSAIDs, MAOIs, adrenoceptor stimulants, and combined methods of hormonal
contraception can cause hypertension while in use.
Heavy alcohol use Steroid use
Nicotine use. Malformed aorta, slow pulse, ischemia:
these cause reduced blood flow to the renal arteries, with physiological
responses as already outlined. Aortic valve disease: unclear etiology.
Coarcation of the aorta Atherosclerosis
Anemia: unclear etiology. Fever: unclear etiology.
White coat hypertension, that is, elevated blood pressure in a clinical
setting but not in other settings, probably due to the anxiety some people
experience during a clinic visit. Perioperative hypertension is
development of hypertension just before, during or after surgery. It may occur
before surgery during the induction of anesthesia; intraoperatively e.g. 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 postoperativ period as fluid is mobilized from the
extravascular space. In addition, hypertension may develop perioperatively
because of discontinuation of long-term antihypertensive medication.
= 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. Another related disorder that causes
hypertension is apparent mineralocorticoid excess syndrome which
is an autosomal recessive disorder that results from mutations in the gene
encoding 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. This effect can also be produced by prolonged ingestion
of liquorice, by causing inhibition of the 11β-hydroxysteroid dehydrogenase
enzyme and likewise leading to secondary apparent mineralocorticoid excess
syndrome. Frequently, if liquorice is the cause of the high blood pressure, a
low blood level of potassium will also be present. Cortisol induced
hypertension cannot be completely explained by the activity of Cortisol on
Aldosterone receptors. Experiments show that treatment with Spironolactone, does
not prevent hypertension with excess cortisol. It seems that inhibition of
nitric oxide synthesis may also play a role in cortisol induced hypertension.
Yet another related disorder causing hypertension is glucocorticoid
remediable aldosteronism, which is an autosomal dominant disorder in which the
increase in aldosterone secretion produced by ACTH is no longer transient,
causing of primary hyperaldosteronism, the Gene mutated will result in an
aldosterone synthase that is ACTH-sensitive, which is normally not.
GRA appears to be the most common monogenic form of human hypertension.
Compare these effects to those seen in Conn's disease, an adrenocortical tumor
which causes excess release of aldosterone, that leads to hypertension.
Another adrenal related cause is Cushing's syndrome which is a disorder
caused by high levels of cortisol. Cortisol is a hormone secreted by the
cortex of the adrenal glands. Cushing's syndrome can be caused by taking
glucocorticoid drugs, or by tumors that produce cortisol or adrenocorticotropic
hormone. More than 80% of patients with Cushing's syndrome develop
hypertension., which is accompanied by distinct symptoms of the syndrome, such
as central obesity, lipodystrophy, moon face, sweating, hirsutism and anxiety.
= Kidney = Other well known causes include diseases
of the kidney. This includes diseases such as polycystic kidney disease which
is a cystic genetic disorder of the kidneys, PKD is characterized by the
presence of multiple cysts in both kidneys, can also damage the liver,
pancreas, and rarely, the heart and brain. It can be autosomal dominant or
autosomal recessive, with the autosomal dominant form being more common and
characterized by progressive cyst development and bilaterally enlarged
kidneys with multiple cysts, with concurrent development of hypertension,
renal insufficiency and renal pain. Or chronic glomerulonephritis which is a
disease characterized by inflammation of the glomeruli, or small blood vessels in
the kidneys. 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. Also, some renal tumors can cause
hypertension. The differential diagnosis of a renal tumor in a young patient with
hypertension includes Juxtaglomerular cell tumor, Wilms' tumor, and renal cell
carcinoma, all of which may produce renin.
Neuroendocrine tumors are also a well known cause of secondary hypertension.
Pheochromocytoma increases secretion of catecholamines such as epinephrine and
norepinephrine, causing 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.
= Medication side effects = Certain medications, including NSAIDs
and steroids can cause hypertension. Other medications include extrogens,
certain antidepressants, 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, 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 ma huang, St John's 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.
= Sleep disturbances = Another common and under-recognized sign
of hypertension is sleep apnea, which is often best treated with nocturnal nasal
continuous positive airway pressure, but other approaches include the Mandibular
advancement splint, UPPP, tonsillectomy, adenoidectomy, septoplasty, or weight
loss. Another cause is an exceptionally rare neurological disease called
Binswanger's disease, causing dementia; it is a rare form of multi-infarct
dementia, and is one of the neurological syndromes associated with hypertension.
= Arsenic exposure = Because of the ubiquity of arsenic in
ground water supplies and its effect on cardiovascular health, low dose arsenic
poisoning should be inferred as a part of the pathogenesis of idiopathic
hypertension. Idiopathic and essential are both somewhat synonymous with
primary hypertension. Arsenic exposure has also many of the same signs of
primary hypertension such as headache, somnolence, confusion, proteinuria
visual disturbances, and nausea and vomiting
= Potassium deficiency = Due to the role of intracellular
potassium in regulation of cellular pressures related to sodium,
establishing potassium balance has been shown to reverse hypertension.
Diagnosis The ABCDE mnemonic can be used to help
determine a secondary cause of hypertension
A: Accuracy, Apnea, Aldosteronism B: Bruits, Bad Kidney
C: Catecholamines, Coarctation of the Aorta, Cushing's Syndrome
D: Drugs, Diet E: Erythropoietin, Endocrine Disorders
References External links
CVPhysiology CNN
Mayo Clinic Hypertension Types