Conn's syndrome belongs among adrenal disorders. It is also referred to as the primary hyperaldosteronism. First, it is necessary to know some basic information about the anatomy and function of adrenal glands.
The adrenal gland is paired organ, which is located above the upper pole of both kidneys. The adrenal glands are composed of cortex and medulla and they produce a number of important hormones. The cortex produces glucocorticoids and mineralocorticoids. The most important glucocorticoids is hormone known as cortisol, which has a great influence on metabolism and immune system. It helps to survive highly stressful situations. Mineralocorticoids, whose main representative is aldosterone, affect the kidneys and blood vessels, reduce loss of sodium into the urine, increase the loss of potassium and elevate the blood pressure. The cortex also produces a small amount of sex hormones.
The production of glucocorticoids is controlled by brain. Kidneys control the production of mineralocorticoids. Hypothalamic substance CRH acts on the pituitary gland, which produces a hormone known as ACTH, which gets into the blood and affects the adrenal glands to produce more cortisol. The kidneys produce a hormone called renin, which gets into the blood and causes increased production of aldosterone.
The Conn's syndrome is caused by a disorder of adrenal glands, which is associated with increased production of aldosterone.
There are more possible causes of aldosterone overproduction. Typically, the reason is a formation of benign adrenal tumors, whose cells kept the ability to produce the hormone. Kidneys detect the high level of serum aldosterone and try to reduce it by decreased production of renin, but it is useless – the tumor tissue does not respond well. Another possibility is the so-called bilateral adrenal hyperplasia, when both adrenal glands enlarge and produce the aldosterone independently of renin. Condition similar to Conn's syndrome may be caused by kidneys that can produce an excessive amount of renin. Increased level of renin causes secondary increase of aldosterone production. This situation may occur for example in narrowing of renal artery.
High level of aldosterone reduces sodium excretion into the urine and on the other side, it increases potassium losses. Sodium ions accumulate in the body and this leads to retention of body fluid and hypertension. The high blood pressure may be asymptomatic or cause symptoms such as headache, fatigue, nosebleeds and others. Long-term untreated hypertension may cause heart failure. Decreased amount of potassium in blood (hypokalemia) manifests with constipation, muscle weakness and sometimes even with dangerous arrhythmias.
We can think about the Conn's syndrome in patients with chronically and unsuccessfully treated hypertension. Blood tests may show abnormally high level of sodium and hypokalemia. The adrenal glands should be examined by an imaging method such as abdominal ultrasound or computed tomography to find a causing tumor.
We can also evaluate the levels of particular hormones in blood, which can help us to confirm the diagnosis. Classic Conn’s syndrome is accompanied with elevated level of aldosterone but decreased level of renin. If both values of aldosterone and renin are high, the problem comes from the kidney.
The therapy of adrenal tumors is primary surgical. After the tumor tissue is removed, the production of aldosterone returns to normal. Tumors of the adrenal try to surgically remove. Reversible enlargement of the adrenal glands can be solved by diuretics such as spironolactone and eplerenone that inhibit the effects of aldosterone. They still have a number of side effects, but it is the best solution. Reversible surgical removal of the adrenal gland is not useful, because of the great importance of their hormones. Bilateral surgical removal of adrenal glands is not preferred (unless necessary) due to their hormonal importance.