Home
/ What Hormone Regulates Potassium Levels and How Does It Work
What Hormone Regulates Potassium Levels and How Does It Work
Potassium
L.J. Appel , in Encyclopedia of Human Nutrition (Third Edition), 2013
Conclusion
Potassium is an essential nutrient that is required for normal cellular function. Although humans evolved on diets rich in potassium, contemporary diets are quite low in potassium. An increased intake of potassium from foods should prevent many of the adverse effects of inadequate potassium intake, which are higher blood pressure levels, greater salt sensitivity, increased risk of kidney stones, and possibly increased bone loss. An inadequate potassium level may also increase the risk of stroke. In view of the high prevalence of elevated blood pressure, stroke, and conditions related to bone demineralization (i.e., osteoporosis and kidney stones) in the general population, individuals should strive to increase their consumption of potassium-rich foods, particularly fruits and vegetables.
The potassium content of the body is maintained through variation of renal excretion. Aldosterone increases the secretion of potassium from connecting segments and collecting ducts of the kidney by acting on the mineralocorticoid receptor (NR3C2) in those segments. Receptor activation promotes expression of the sodium/potassium exchanging ATPase (EC3.6.3.9). The renin–angiotensin system links aldosterone concentration to potassium concentration in blood. Glycorrhizic acid in licorice increases both renal and extrarenal potassium losses by inhibiting renal 11β-hydroxysteroid dehydrogenase type 2 (EC1.1.1.146) and slowing the conversion of cortisol to its metabolite cortisone (Serra et al., 2002). Cortisol, but not cortisone, strongly activates the mineralocorticoid receptor. Catecholamines and insulin promote the redistribution of potassium into liver and skeletal muscles.
In Clinical Veterinary Advisor: Birds and Exotic Pets, 2013
Physiology
•
Potassium is largely—approximately 98%—found extracellularly. The proper concentration is maintained at the cellular level by the Na+/K+-ATPase (sodium/potassium–adenosine triphosphatase) pump, located on cell membranes, which removes 3 Na+ ions from the cell in exchange for 2 K+ ions. This is especially vital in nerve cells for maintaining the proper electrochemical membrane potential.
•
The potassium concentration can be affected at the cellular level by a number of factors. The pH of the extracellular environment is one of the major influences on potassium serum concentration. Acidotic conditions promote cellular uptake of H+ to maintain homeostasis. For each H+ taken up by the cells, a K+ is moved extracellularly to preserve electroneutrality. Alkalosis has the opposite effect, promoting cellular uptake of K+ in exchange for H+, although this effect is not as strong as the response to acidosis. Increases in sodium bicarbonate cause a decrease in potassium, both directly and by creating an alkalotic environment. Insulin causes cells to take up K+. Insulin increases the activity of the membrane-bound Na+/H+ exchanger, causing an increase in intracellular Na, which increases the activity of the Na+/K+-ATPase pump, leading to a decrease in extracellular K+. Catecholamines decrease K+ concentrations by B2 activation of adenylate cyclase, which stimulates the action of the Na+/K+-ATPase pump. Elevations in thyroid hormones can decrease potassium by upregulating the Na+/K+-ATPase pump.
•
The body maintains potassium concentration primarily through the action of the kidneys. Potassium is freely filtered by the glomerulus. It is actively reabsorbed in the proximal tubules, but regulation occurs mostly at the collecting ducts. Both aldosterone and antidiuretic hormone (ADH) increase potassium loss into the urine. Alkalotic urine also promotes potassium loss due to decreased resorption. Increased dietary intake of potassium leads to increased urinary loss.
S.C. Gad , in Encyclopedia of Toxicology (Third Edition), 2014
Abstract
Potassium (CASRN 7440-09-7) is a requirement for most living things, and is found in an abundance of approximately 2.5% in the Earth's crust. Discovered in 1807 by Sir Humphry Davy, this metal is also among the most highly reactive, being particularly explosive when coming into contact with water. While the toxicity of this metal is low enough such that there are no exposure guidelines set by regulatory agencies, there are dangers of upsetting the balance between it and sodium in the human body. Many of its salts have common uses in industrial applications.
Shayne C. Gad , in Encyclopedia of Toxicology (Second Edition), 2005
Human
Excess intake of potassium, reduced renal excretion of potassium, or both can lead to hyperkalemia, which can lead to serious arrhythmia and death. The toxicity of excess potassium can be exacerbated by aldosterone antagonist drugs. Slow-release potassium tablets in overdose are a frequent cause.
Periodically, solutions containing a relatively high concentration of a potassium salt are sold as a nutritional supplement. In light of the fact that ingestion of additional potassium can upset the sodium–potassium ratio, potassium supplements are only indicated on the advice of a physician. Unusually high intake of potassium can cause abnormal EKG readings (T-waves will be evaluated and P-waves depressed). Ventricular fibrillation can result and lead to cardiac arrest. A large increase (∼18 g day−1) may produce neuromuscular weakness or paralysis.
Potassium permanganate is a mucous membrane irritant. Taken internally, it can be corrosive to the stomach. It is poorly absorbed, but it can cause nervous system symptoms and increased methemoglobin levels.
Hyperkalemia: Increased potassium concentration in the blood
•
Normokalemia: Normal potassium concentration in the blood
•
Hypokalemia: Decreased potassium concentration in the blood
Synonym(s)
Typical Normal Range (US Units; SI Units)
2.4 to 4.7 mEq/L; 2.4 to 4.7 mmol/L
Physiology
Potassium is critical for many biochemical cellular reactions. It is ingested daily and renal excretion is regulated by aldosterone. Potassium is also lost in feces and sweat. Most of the body's potassium is found intracellularly. Serum (extracellular) potassium is less than 2% of the whole body potassium.
Causes of Abnormally High Levels
•
Shift from intracellular fluid (ICF) to extracellular fluid (ECF): Metabolic acidosis, hyperkalemic periodic paralysis (HYPP) in Quarter Horses, vigorous exercise, muscle damage, severe cellular damage/tissue necrosis, intravascular hemolysis, and diabetes mellitus
Increased absorption: Administration of potassium-rich fluids
Next Diagnostic Step to Consider if Levels High
Review history, clinical signs, complete blood count, biochemistry profile, urinalysis, and rectal examination. Abdominocentesis and fluid creatinine concentration for uroperitoneum, imaging, blood gas analysis, urine fractional clearance of potassium for renal disease, electromyography or DNA blood test for HYPP, adrenocorticotropic hormone (ACTH) stimulation test for hypoadrenocorticism
Causes of Abnormally Low Levels
•
Shift from ECF to ICF: Acute metabolic alkalosis, administration of insulin and/or glucose, endotoxemia
Increased excretion/loss/sequestration: Diarrhea, excessive sweating/salivation, peritonitis, furosemide or thiazide administration, post urethral obstruction diuresis, excessive and rapid bicarbonate administration, ketonuria, lactaturia, bicarbonaturia, renal tubular acidosis, hyperaldosteronism, ileus, torsion, volvulus
•
Other: Endogenous release or exogenous administration of catecholamines
Next Diagnostic Step to Consider if Levels Low
Review history, clinical signs, complete blood count, biochemistry profile, urinalysis, and rectal examination. Urinary fractional clearance for whole body deficiency, abdominocentesis for peritonitis, blood gas analysis, measurement of aldosterone concentration
Drug Effects on Levels
•
Increase: Trimethoprim
•
Decrease: Thiazide diuretics, furosemide
Specimen and Processing Considerations
Lab Artifacts That May Interfere With Readings of Levels of This Substance (and How—Artificially Elevated vs. Depressed)
•
Increase: In vitro hemolysis, delayed serum separation from clot, leukocytosis, thrombocytosis
•
Serum potassium will be slightly higher than plasma potassium due to platelet release of potassium during clotting.
Sample for Collection (Type of Specimen, Color Tube) and Any Special Specimen Handling Notes
•
Serum preferred. Do not use K3EDTA tubes.
•
Methodology: Potentiometry and flame photometry
Pearls
•
Hypokalemia may only become apparent as fluids and electrolyte losses are replaced.
•
Decreased dietary intake plus loss equals marked hypokalemia.
•
Hypokalemia may not correlate or predict whole body potassium deficiency.
•
Consider the acid-base status when interpreting abnormal potassium concentrations (movement of potassium between intracellular and extracellular compartments). If the acid-base status is normal, then serum potassium tends to reflect total body potassium.
Robert J. Van Saun , in Llama and Alpaca Care, 2014
Potassium
Potassium is the major intracellular cation in the body. Primary roles for potassium include acid–base balance and maintenance of electrochemical gradients across cell membranes. Potassium is readily absorbed from the diet and excreted in urine. Dietary potassium deficiency is not typically a problem in forage-based diets but may be in excess when highly fertilized forages are consumed. Excess potassium will antagonize magnesium availability and may interfere with calcium homeostasis by altering acid–base status and sensitivity of parathormone-vitamin D interaction. Excess dietary potassium is excreted in urine resulting in higher urine pH, which might predispose animals to struvite crystal formation. Male animals consuming highly fertilized grass forages containing high nitrogen, phosphorus, and potassium are at greater risk for struvite urolithiasis. Potassium requirement is similar for maintenance, growth, and reproduction. A higher potassium requirement is suggested for lactation to account for losses in milk.
Julian L. Seifter , in Goldman's Cecil Medicine (Twenty Fourth Edition), 2012
Importance of Potassium
Potassium is essential for a number of critical body functions, including enzymatic reactions that regulate protein synthesis, glycogen synthesis, cell growth, and cell division. The ability of cells to take up or extrude potassium contributes to the regulation of cell volume during periods of osmotic stress. In excitable cells, such as cardiac myocytes, the relationship of intracellular to extracellular potassium concentrations is critical in establishing the resting membrane potential, which normally may approach the Nernst equilibrium potential for potassium. Because larger percentage changes can occur in the extracellular potassium concentration compared with the intracellular concentration, changes in extracellular potassium have the greatest impact on the electrical potential difference across cell membranes. The serum potassium itself has effects on conductance of potassium through specific K+ channels.
Potassium is also an important local mediator of vascular tone in muscle beds. During exercise, local extracellular potassium concentrations may rise to as high as 10 mmol/L, thereby causing local vasodilation to allow more blood supply to the exercising muscle. Very little of that potassium remains within the total extracellular fluid, so severe hyperkalemia does not usually occur with exercise. The trained athlete develops an adaptive increase in Na+, K+-ATPase to allow for efficient reuptake of potassium into muscle cells. The importance of adequate potassium stores to muscle function is well known to experienced marathoners, and overexertion of muscles in a state of potassium depletion can lead to rhabdomyolysis.
Nutrition and Health | Nutritional and Health-Promoting Properties of Dairy Products: Bone Health
A. Zittermann , in Encyclopedia of Dairy Sciences (Second Edition), 2011
Potassium Content of Dairy Products
Potassium appears to play an important role in protecting against calcium loss from the renal acid load of protein. The mammary gland is able to concentrate the potassium content against a high serum gradient. Frequent intake of certain dairy products like milk and yogurt can significantly contribute to the total daily potassium intake of 2–3 g. Epidemiologic data indicate a protective effect of potassium intake on bone density. Administration of potassium to postmenopausal women at significantly higher levels than the recommended protein intake has been found to decrease urinary excretion of the bone resorption marker hydroxyproline and increase serum osteocalcin, a marker of bone formation.
E. Alexander , ... Y.C. Wang , in Encyclopedia of Food and Health, 2016
Potassium
Potassium lowers BP through its vasodilating action and its natriuretic effects: the more potassium consumed, the higher the volume of sodium excreted in urine. Dietary potassium exerts a dose-dependent inhibitory effect on sodium sensitivity. The AHA recommends 4.7 mg day− 1 of potassium to help control BP, and several guidelines recommend food sources of potassium (beans, dark leafy greens such as spinach, yogurt and milk, bananas, and winter squash) rather than supplements. Systematic evidence reviews suggest that potassium is associated with lower BP among individuals with hypertension, but estimates of the BP-lowering effect for individuals with BP in the normal range are mixed.