What is Conn's syndrome?
The adrenal glands are orange-colored endocrine glands that are located on the top of both kidneys. The adrenal glands are triangular shaped and measure about one-half inch in height and three inches in length. Each gland consists of a medulla that is surrounded by the cortex. The medulla is responsible for producing epinephrine also known as adrenaline. The
adrenal cortex produces other hormones necessary for fluid and salt balance in the body such as cortisone and aldosterone. Disorders of either the cortex or the medulla can result in hypertension. Also known as primary hyperaldosteronism, Conn's syndrome is a disease of the adrenal glands involving excess production of a hormone, called aldosterone. Another name for the condition is primary hyperaldosteronism.
Primary hyperaldosteronism accounts for less than one percent of all cases of hypertension. It is more common in females than males (2.5:1 ratio). It can occur at any age, but most commonly when a person is in their 30s and 40s. The majority of cases are sporadic, but one hereditary cause has been identified:?glucocorticoid remediable aldosteronism (GRA). GRA is caused by a rare gene where aldosterone production is controlled by the pituitary gland rather than by the kidney. It can also be caused by adrenal cancers or an enlarged organ due to increased cell production (hyperplasia). Other causes of hyperaldosteronism include any condition that decreases blood flow to the kidney, including dehydration, kidney artery constriction, cardiac failure, shock, liver disease, pregnancy and renin-secreting kidney tumors.
Conn's Syndrome is a condition where the adrenal glands over produce the mineralocorticoid hormone aldosterone. This hormone acts in conjunction with renin and angiotensin to regulate the volume of circulating blood through subtle alterations in the amount of sodium and hence water reabsorption in the kidneys. Aldosterone increases the amount of sodium reabsorbed in the kidney and by osmosis draws water along with it. This action is usually counterbalanced to homeostatically maintain normal blood volume. However, in Conn's Syndrome the cells of the adrenal cortex which secrete aldosterone multiply and secrete independently of their normal regulation. As a consequence, blood volume increases and the person becomes, usually severely, hypertensive.
What causes Conn's syndrome (primary hyperaldosteronism)?
The most common cause of Conn's syndrome is an aldosterone-producing tumor of the adrenal gland. Women between the ages of 30 and 50 are at highest risk for developing Conn's syndrome.
The excess secretion of the hormone aldosterone into the blood is from an abnormal adrenal gland or glands. Two types of abnormality are seen: a benign tumour of one adrenal, called an adenoma or a general enlargement of both adrenals, called hyperplasia. The underlying reasons for the development of an adenoma or hyperplasia are not known.
What are the symptoms of Conn's syndrome (primary hyperaldosteronism)?
Symptoms of Conn's syndrome include high blood pressure, headache, tiredness, and excessive urination (often during the night). Also, the level of potassium in the blood may be decreased. Other symptoms may occur because high aldosterone levels in the blood act on the kidney to increase the loss of the mineral potassium in the urine. This in turn may lead to a fall
in
blood potassium, resulting in tiredness, muscle weakness and passing of large
volumes of urine (polyuria), especially at night (nocturia). However, these
symptoms are also found in many other conditions (for example, diabetes mellitus
or hypercalcaemia) and do not, by themselves, establish a diagnosis of Conn's
syndrome. Also, many patients with proven Conn's syndrome do not have a low
blood potassium level.
In hyperaldosteronism, excess aldosterone leads to an inappropriate salt reabsorption, which increases the extracellular fluid volume until the kidneys can respond appropriately. Patients typically have mild to moderate hypertension. Primary hyperaldosteronism can be distinguished from basic hypertension through blood tests. In general, hyperaldosteronism is unresponsive to standard medical therapy used to prevent or reduce high blood pressure.
Mild hypernatremia (high blood sodium), hypokalemia (low blood potassium), hyperkaluria (high urine potassium) and high levels of alkalinity are the electrolyte abnormalities commonly seen with excess aldosterone. These contribute the following symptoms: muscle weakness, frequent urination, nighttime urination, headache, excessive thirst, pins and needles sensation, visual disturbances, temporary paralysis, muscle twitching and cramps. The severity of these symptoms may be highly variable depending on the degree of electrolyte abnormality.
How is Conn's syndrome (primary hyperaldosteronism) diagnosed?
Conn's syndrome should be suspected in all patients with high blood pressure. Traditional teaching has been to limit investigation for Conn's syndrome to patients who have a low blood potassium, or in whom blood pressure which is moderate to severe (>160/110mmHg), or is difficult to control with medication. However, using these criteria, many patients with Conn's syndrome will not be diagnosed. For example, about 40 per cent of patients with proven Conn's syndrome have normal blood potassium levels. The most rigorous method of diagnosis is to measure the blood levels of two hormones: aldosterone and renin (which plays a role in stimulating aldosterone production). In Conn's syndrome, the aldosterone level is elevated and the renin level is low or undetectable.
What're the treatments for Conn's syndrome (primary hyperaldosteronism)?
Conn's syndrome resulting from a tumor is usually treated by removing an adrenal gland (unilateral adrenalectomy). This surgery may be performed with an open or laparoscopic approach.
The commonest cause of high blood pressure is essential hypertension, and this may mimic Conn's syndrome. Thus, high blood pressure and
low blood potassium may be due to essential hypertension, which is being treated
with diuretic drugs that cause a loss of potassium in the urine. In addition,
plasma renin activity may be suppressed by some drugs that are commonly used to
treat hypertension (for example, beta-blockers). The suppression may mislead
physicians to an incorrect diagnosis of primary hyperaldosteronism (Conn's
syndrome). There are also a few very rare conditions your doctor might need to
exclude.
In general, patients experience rapid and uneventful postoperative recovery. Of the patients who undergo unilateral adrenalectomy for primary hyperaldosteronism, hypertension is completely resolved or significantly improved in 80 to 90 percent. The preoperative plasma renin activity (PRA) level is the best predictor of postoperative blood pressure outcome. As a result, the cured patients have lower pre-surgical PRA levels than those who are not cured. Even after surgery, some patients have high blood pressure and require medication for hours or weeks until their blood pressure returns to normal. Blood pressure and serum electrolytes should be monitored after surgery and/or after the start of medical therapy.
Up to 5 percent of patients may suffer from ongoing high blood pressure. The reason for this is not fully understood, but some experts believe this may be a result of chronic, irreversible kidney damage from the primary hyperaldosteronism.
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