Magnesium deficiency is an electrolyte disturbance in which there is a low level of magnesium in the body. It can result in numerous symptoms. Symptoms include tremor, nystagmus, seizures, and cardiac arrest including torsade de pointes.
Causes include alcoholism, starvation, diarrhea, increased urinary loss, and poor absorption from the intestines. The diagnosis is typically based on finding low blood magnesium levels (hypomagnesemia). Normal magnesium levels are between 1.46-2.68 mg/dL (0.6-1.1 mmol/L) with levels less than 1.46 mg/dL (0.6 mmol/L) defining hypomagnesemia. Specific electrocardiogram (ECG) changes may be seen.
Treatment is generally by increasing of magnesium in diet or supplements either by mouth or intravenously. For those with severe disease intravenous magnesium sulfate may be used.
Video Magnesium deficiency
Signs and symptoms
Deficiency of magnesium can cause tiredness, generalized weakness, muscle cramps, abnormal heart rhythms, increased irritability of the nervous system with tremors, paresthesias, palpitations, low potassium levels in the blood, hypoparathyroidism which might result in low calcium levels in the blood, chondrocalcinosis, spasticity and tetany, migraines, epileptic seizures, basal ganglia calcifications and in extreme and prolonged cases coma, intellectual disability or death. Magnesium plays an important role in carbohydrate metabolism and its deficiency may worsen insulin resistance, a condition that often precedes diabetes, or may be a consequence of insulin resistance.
People being treated on an intensive care unit who have a low magnesium level may have a higher risk of requiring mechanical ventilation, and death.
Maps Magnesium deficiency
Causes
Magnesium deficiency is not uncommon in hospitalized patients. Elevated levels of magnesium (hypermagnesemia), however, are nearly always caused by a medical treatment. Up to 12 percent of all people admitted to hospital and as high as 60-65% of people in the intensive care unit (ICU) have hypomagnesemia. Hypomagnesemia is probably underdiagnosed, as testing for serum magnesium levels is not routine.
Low levels of magnesium in blood may mean that there is not enough magnesium in the diet, the intestines are not absorbing enough magnesium, or the kidneys are excreting too much magnesium. Deficiencies may be due to the following conditions:
Drugs
- Alcoholism. Hypomagnesemia occurs in 30% of alcohol abusers and in 85% of delirium tremens inpatients, due to malnutrition and chronic diarrhea. Alcohol stimulates the kidneys' excretion of magnesium, which is also increased because of alcoholic and diabetic ketoacidosis, low blood phosphate levels, and hyperaldosteronism resulting from liver disease. Also, hypomagnesemia is related to thiamine deficiency because magnesium is needed for transforming thiamine into thiamine pyrophosphate.
Medications
- Loop and thiazide diuretic use (the most common cause of hypomagnesemia)
- Antibiotics (i.e. aminoglycoside, amphotericin, pentamidine, gentamicin, tobramycin, viomycin) block resorption in the loop of Henle. 30% of patients using these antibiotics have hypomagnesemia.
- Long term use of proton-pump inhibitors such as omeprazole.
- Other drugs.
- Digitalis, displaces magnesium into the cell. Digitalis causes an increased intracellular concentration of sodium, which in turn increases intracellular calcium by passively decreasing the action of the sodium-calcium exchanger in the sarcolemma. The increased intracellular calcium gives a positive inotropic effect.
- Adrenergics, displace magnesium into the cell
- Cisplatin, stimulates kidney excretion
- Ciclosporin, stimulates kidney excretion
- Mycophenolate mofetil
Genetic causes
- Gitelman-like diseases, which include the syndromes caused by genetic mutations in SLC12A3, CLNCKB, BSND, KCNJ10, FXYD2, HNF1B or PCBD1. In these diseases, the hypomagnesemia is accompanied by other defects in electrolyte handling such as hypocalciuria and hypokalemia. The genes involved in this group of diseases all encode proteins that are involved in reabsorbing electrolytes (including magnesium) in the distal convoluted tubule of the kidney.
- Hypercalciuric hypomagnesemic syndromes, which encompass the syndromes caused by mutations in CLDN16, CLDN19, CASR or CLCNKB. In these diseases, reabsorption of divalent cations (such as magnesium and calcium) in the thick ascending limb of Henle's loop of the kidney is impaired. This results in loss of magnesium and calcium in the urine.
- Mitochondriopathies, such as caused by mutations in SARS2, MT-TI or as seen with Kearns-Sayre syndrome.
- Other genetic causes of hypomagnesemia, such as mutations in TRPM6, CNNM2, EGF, EGFR, KCNA1 or FAM111A. Many of the proteins encoded by these genes play a role in the transcellular absorption of magnesium in the distal convoluted tubule.
Metabolic abnormalities
- Insufficient selenium, vitamin D, sunlight exposure or vitamin B6.
- Gastrointestinal causes: the distal digestive tract secretes high levels of magnesium. Therefore, secretory diarrhea can cause hypomagnesemia. Thus, Crohn's disease, ulcerative colitis, Whipple's disease and celiac sprue can all cause hypomagnesemia.
- Postobstructive diuresis, diuretic phase of acute tubular necrosis (ATN) and kidney transplant.
Other
- Acute myocardial infarction: within the first 48 hours after a heart attack, 80% of patients have hypomagnesemia. This could be the result of an intracellular shift because of an increase in catecholamines.
- Malabsorption
- Acute pancreatitis
- Fluoride poisoning
- Massive transfusion (MT) is a lifesaving treatment of hemorrhagic shock, but can be associated with significant complications.
Pathophysiology
Magnesium is a co-factor in over 300 functions in the body regulating many kinds of biochemical reactions. It is involved in protein synthesis, muscle and nerve functioning, bone development, energy production, the maintenance of normal heart rhythm, and the regulation of glucose and blood pressure, among other important roles. Low magnesium intake over time can increase the risk of illnesses, including high blood pressure and heart disease, diabetes mellitus type 2, osteoporosis, and migraines.
There is a direct effect on sodium (Na), potassium (K), and calcium (Ca) channels. Magnesium has several effects:
Potassium
Potassium channel efflux is inhibited by magnesium. Thus hypomagnesemia results in an increased excretion of potassium in kidney, resulting in a hypokalaemia. This condition is believed to occur secondary to the decreased normal physiologic magnesium inhibition of the ROMK channels in the apical tubular membrane.
In this light, hypomagnesemia is frequently the cause of hypokalaemic patients failing to respond to potassium supplementation. Thus, clinicians should ensure that both Magnesium and Potassium is replaced when deficient. Patients with diabetic ketoacidosis should have their magnesium levels monitored to ensure that the serum loss of potassium, which is driven intracellularly by insulin administration, is not exacerbated by additional urinary losses.
Calcium
Release of calcium from the sarcoplasmic reticulum is inhibited by magnesium. Thus hypomagnesemia results in an increased intracellular calcium level. This inhibits the release of parathyroid hormone, which can result in hypoparathyroidism and hypocalcemia. Furthermore, it makes skeletal and muscle receptors less sensitive to parathyroid hormone.
Arrhythmia
Magnesium is needed for the adequate function of the Na+/K+-ATPase pumps in cardiac myocytes, the muscles cells of the heart. A lack of magnesium inhibits reuptake of potassium, causing a decrease in intracellular potassium. This decrease in intracellular potassium results in a tachycardia.
Pre-eclampsia
Magnesium has an indirect antithrombotic effect upon platelets and endothelial function. Magnesium increases prostaglandins, decreases thromboxane, and decreases angiotensin II, microvascular leakage, and vasospasm through its function similar to calcium channel blockers. . Convulsions are the result of cerebral vasospasm. The vasodilatatory effect of magnesium seems to be the major mechanism.
Asthma
Magnesium exerts a bronchodilatatory effect, probably by antagonizing calcium-mediated bronchoconstriction.
Neurological effects
- reducing electrical excitation
- modulating release of acetylcholine
- antagonizing N-methyl-D-aspartate (NMDA) glutamate receptors, an excitatory neurotransmitter of the central nervous system and thus providing neuroprotection from excitoxicity.
Homeostasis
Magnesium is abundant in nature. It can be found in green vegetables, chlorophyll, cocoa derivatives, nuts, wheat, seafood, and meat. It is absorbed primarily in the duodenum of the small intestine. The rectum and sigmoid colon can absorb magnesium. Forty percent of dietary magnesium is absorbed. Hypomagnesemia stimulates and hypermagnesemia inhibits this absorption.
The body contains 21-28 grams of magnesium (0.864-1.152 mol). Of this, 53% is located in bone, 19% in non-muscular tissue, and 1% in extracellular fluid. For this reason, blood levels of magnesium are not an adequate means of establishing the total amount of available magnesium.
In terms of serum magnesium, the majority is bound to chelators, including {removed ATP and ADP which are not present in serum at significant levels and therefore cannot be significant chelators of magnesium in serum}proteins and citrate. Roughly 33% is bound to proteins, and 5-10% is not bound. This "free" magnesium is essential in regulating intracellular magnesium. Normal plasma Mg is 1.7-2.3 mg/dl (0.69-0.94 mmol/l).
The kidneys regulate the serum magnesium. About 2400 mg of magnesium passes through the kidneys daily, of which 5% (120 mg) is excreted through urine. The loop of Henle is the major site for magnesium homeostasis, and 60% is reabsorbed.
Magnesium homeostasis comprises three systems: kidney, small intestine, and bone. In the acute phase of magnesium deficiency there is an increase in absorption in the distal small intestine and tubular resorption in the kidneys. When this condition persists, serum magnesium drops and is corrected with magnesium from bone tissue. The level of intracellular magnesium is controlled through the reservoir in bone tissue.
Diagnosis
Magnesium deficiency is not easy to directly measure. Typically the diagnosis is based on finding low blood magnesium levels (hypomagnesemia). Specifically by finding a plasma magnesium concentration of less than 0.6 mmol/L (1.46 mg/dl). Since most magnesium is inside cells, occationally a body deficit can be present with a normal plasma concentration.
The ECG may show a tachycardia with a prolonged QT interval, which has been noted in proton pump inhibitor-associated hypomagnesemia.
Treatments
Treatment of hypomagnesemia depends on the degree of deficiency and the clinical effects. Replacement by mouth is appropriate for people with mild symptoms, while intravenous replacement is recommended for people with severe effects.
Numerous oral magnesium preparations are available. In two trials of magnesium oxide, one of the most common forms in magnesium dietary supplements because of its high magnesium content per weight, was less bioavailable than magnesium citrate, chloride, lactate or aspartate. Magnesium citrate has been reported as more bioavailable than oxide or amino-acid chelate forms.
Intravenous magnesium sulfate (MgSO4) can be given in response to heart arrhythmias to correct for hypokalemia, preventing pre-eclampsia, and has been suggested as having a potential use in asthma.
Food
Food sources of magnesium include leafy green vegetables, soybeans, nuts, and fruits and egg
Epidemiology
57% of the US population does not meet the US RDA for dietary intake of magnesium. The kidneys are very efficient at maintaining body levels, except in cases where the diet is deficient due to the use of certain medications such as proton-pump inhibitors or chronic alcoholism.
History
Magnesium deficiency in humans was first described in the medical literature in 1934.
Terminology
Magnesium deficiency (or depletion) refers to low total body levels of magnesium which is usually determined by finding low blood levels (hypomagnesemia). Magnesium deficiency encompasses a broader scope, and includes disorders of magnesium metabolism and low intracellular storage. Hypomagnesemia refers only to blood levels of magnesium. Magnesium deficiency can be present without hypomagnesemia, and hypomagnesemia can be present without magnesium deficiency. As a disorder of metabolism, magnesium deficiency can be much harder to treat than hypomagnesemia.
In plants
Magnesium deficiency is a detrimental plant disorder that occurs most often in strongly acidic, light, sandy soils, where magnesium can be easily leached away. Magnesium is an essential macronutrient constituting 0.2-0.4% of plants' dry matter and is necessary for normal plant growth. Excess potassium, generally due to fertilizers, further aggravates the stress from magnesium deficiency, as does aluminium toxicity.
Magnesium has an important role in photosynthesis because it forms the central atom of chlorophyll. Therefore, without sufficient amounts of magnesium, plants begin to degrade the chlorophyll in the old leaves. This causes the main symptom of magnesium deficiency, interveinal chlorosis, or yellowing between leaf veins, which stay green, giving the leaves a marbled appearance. Due to magnesium's mobile nature, the plant will first break down chlorophyll in older leaves and transport the Mg to younger leaves which have greater photosynthetic needs. Therefore, the first sign of magnesium deficiency is the chlorosis of old leaves which progresses to the young leaves as the deficiency progresses. Magnesium also acts as an activator for many critical enzymes, including ribulosbiphosphate carboxylase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC), both essential enzymes in carbon fixation. Thus low amounts of Mg lead to a decrease in photosynthetic and enzymatic activity within the plants. Magnesium is also crucial in stabilizing ribosome structures, hence, a lack of magnesium causes depolymerization of ribosomes leading to premature aging of the plant. After prolonged magnesium deficiency, necrosis and dropping of older leaves occurs. Plants deficient in magnesium also produce smaller, woodier fruits.
Magnesium deficiency may be confused with zinc or chlorine deficiencies, viruses, or natural aging since all have similar symptoms. Adding Epsom salts (as a solution of 25 grams per liter or 4 oz per gal) or crushed dolomitic limestone to the soil can rectify magnesium deficiencies. For a more organic solution, applying home-made compost mulch can prevent leaching during excessive rainfall and provide plants with sufficient amounts of nutrients, including magnesium.
See also
- Magnesium in biology
- Hypermagnesemia
References
External links
- Magnesium
- Magnesium at Lab Tests Online
Source of article : Wikipedia
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