There is more potassium inside your body's cells than outside. This varied distribution of potassium across the cell membrane favors the outflow of potassium from the cell. When potassium leaves the cell, it enters the circulation and is eventually secreted into the urine. When the outflow of urine is unobstructed, decreased formation of urine is associated with increased potassium excretion.
Potassium Regulation
The adrenal glands and kidneys are the most important organs involved with potassium regulation. The adrenal glands -- or more specifically, the adrenal cortex -- produce aldosterone, a steroid hormone released when blood potassium is increased or when blood flow to the kidneys is decreased; without receptors in the kidneys, aldosterone would have no effect on potassium regulation. Decreased blood flow to the kidneys results in decreased urine formation.
Causes of Decreased Urination and Increased Potassium Excretion
Circulatory shock, or severely decreased blood pressure, results in the lack of effective blood circulation to organs of the body, including the kidneys. In circulatory shock, the kidneys respond by triggering the eventual release of aldosterone. Circulatory shock can be caused by infection, severe hemorrhage, dehydration and heart failure. A severe allergic reaction can also cause excessive widening of blood vessels, which reduces blood pressure and blood flow to the kidneys.
Potassium excretion and Increased Urination
Increased excretion of potassium can occur as a consequence of diuretic use; diuretics are used in the treatment of fluid overload and hypertension. All diuretics result in increased water excretion, and therefore increased urine formation. Furosemide -- a loop diuretic -- directly causes the excretion of potassium in the kidneys. Diabetes, which causes increased urination, is associated with hyperkalemia, or increase blood potassium, due to lack of insulin and reduced aldosterone secretion; diabetes results in decreased excretion of potassium.
Symptoms and Complications Associated with Low Blood Potassium
Potassium is important to the functioning of the heart, nerves and skeletal muscles. Low potassium can be life-threatening due to heart dysfunction; symptoms associated with heart dysfunction include palpitations, or the sensation of the heart beating outside the chest, and arrhythmias or dysregulation of heart rhythm. Other symptom of hypokalemia, or low blood potassium, include fatigue and muscle weakness. Hypokalemia may also result in intestinal obstruction, due to paralysis of intestinal muscles.
References
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper M.D., et al.; 2005
- "Davidson's Principles & Practice of Medicine; Nicholas A. Boon; 2006
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