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JUNE 2017 | Published by RCPA

Issue #070

Hypertension may be a red flag that something else is going wrong

Hypertension may be a red flag that something else is going wrong

High blood pressure (hypertension) is common, and doctors mostly deal with a form called primary (or essential) hypertension. Its exact cause is unknown, but the complications of long-standing or severe hypertension include different types of strokes, heart failure, kidney damage and leg ulcers from blood vessel damage.

Dr Lee Price, Chemical Pathologist and Endocrinologist at Sullivan Nicolaides Pathology in Brisbane, says primary hypertension is managed with lifestyle changes and antihypertensive medication to normalise blood pressure. He confirms that patients occasionally have an identifiable cause for their hypertension, and this is called secondary hypertension.

“Secondary hypertension occurs in pregnancy and kidney disease, but it may also be due to excess production of hormones. Many diseases can cause it including hyperaldosteronism (Conn’s syndrome), Cushing’s syndrome and phaeochromocytoma, to name just three.”

Hyperaldosteronism is the most common hormonal cause for secondary hypertension. It occurs when the adrenal glands make too much of the hormone aldosterone.

“Aldosterone regulates the amount of salt and water reabsorbed into the bloodstream from the kidneys. Excessive secretion increases salt reabsorption into the blood and decreases blood potassium levels. The result is a higher blood pressure partly due to the extra fluid retained with the increased salt. Blood tests to diagnose hyperaldosteronism measure the levels of aldosterone, renin (a hormone made by the kidney) and potassium,” explains Dr Price.

In Cushing’s syndrome, the adrenal gland produces excessive quantities of cortisol which swamps the aldosterone receptor in the kidney, resulting in hypertension.

“Excess cortisol production also results in diabetes, osteoporosis, weight gain and muscle weakness. A doctor can screen for Cushing’s syndrome with specific blood, urine and saliva tests.”

Dr Price says about 0.5% of hypertensive patients have a tumour called a phaeochromocytoma that produces excessive amounts of the hormones adrenalin and noradrenalin.

“These patients have hypertension which can be very severe, as well as other features including headaches, racing heart and heart failure. This can be a dangerous condition and needs to be diagnosed as soon as possible. Cure can be achieved by removing the tumour that is most often found in the adrenal glands. The best screening test for a phaeochromocytoma is measuring levels of metanephrines (by-products of the metabolism of adrenalin and noradrenalin) via a blood test,” says Dr Price.

Hypertension can also rarely occur as a side effect of a medicine or chemical substance, including from an ingredient found in liquorice.

“The ingredient in liquorice that causes hypertension is glycyrrhizic acid. It essentially switches off a protective ‘gatekeeper’ enzyme to the aldosterone receptor in the kidneys. This protective enzyme opens the gate to allow aldosterone access to the receptor but prevents cortisol, which is in much higher concentrations in the body, from gaining access. The liquorice ingredient inactivates the gatekeeper allowing cortisol to flood the aldosterone receptor, and this causes hypertension.”

Hypertension is clearly a red flag that something else is going wrong in the body, and the skill is in identifying what that ‘something’ is. Whether it’s primary or secondary hypertension, the long-term consequences of this insidious disease are reason enough to investigate the cause and initiate treatment or preventive measures as early as possible.




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