What Is Hypomagnesemia?
Hypomagnesemia is an electrolyte disorder characterized by low levels of serum magnesium. The normal serum magnesium level ranges from 1.46 to 2.68 mg/dl.
What Is the Normal Physiology of Magnesium?
Magnesium is an important cofactor in regulating many biochemical reactions. It is the fourth major cation and the second most intracellular element in the body. Magnesium plays an important role in regulating protein synthesis, blood glucose levels, muscle and nerve function, and regulating blood pressure. Magnesium is principally absorbed from the small intestine; around 30 to 40 percent of magnesium is absorbed from the typical nutritious diet.
Magnesium is stored in the bones, and the excess magnesium is excreted in the urine and feces. The kidney plays an important role in regulating magnesium homeostasis where it conserves magnesium by reabsorption of magnesium from the urine formed in the tubules of the kidney, and in the case of magnesium, excess kidneys help in excreting them in the urine.
What Is the Epidemiology of Hypomagnesemia?
Hypomagnesemia is reported to be seen in two percent of the general population and 12 percent of hospitalized patients. It is more prevalent among the patients in the intensive care unit who need complete nutritious supply through the parenteral route, and it is reported to be around 60 to 65 percent among them. Seen among 30 to 80 percent of patients with chronic alcohol usage and 25 percent of patients with diabetes.
What Is the Etiology of Hypomagnesemia?
The causes of hypomagnesemia can be categorized into three types,
Hypomagnesemia Due to Decreased Intake:
Starvation - It is seen in patients who have been starving for a long time due to diminished nutrition supply.
Alcoholism - It is common among chronic alcoholics as it causes loss of magnesium from the tissues, and it is excreted in the urine.
Hospitalized Patients - It is more common among patients in the intensive care unit who are completely dependent on parenteral nutrition.
Hypomagnesemia Due to Increased Excretion:
The excretion or loss of magnesium can occur in two ways, either gastrointestinal or renal.
Diarrhea - Acute diarrhea can cause loss of magnesium.
Crohn's Disease - In this condition, there is chronic diarrhea leading to progressive loss of magnesium.
Ulcerative Colitis - Magnesium loss occurs as a result of chronic diarrhea.
Gitelman Syndrome - Wasting of magnesium occurs along with potassium in this syndrome.
Bartter Syndrome - This is an autosomal recessive disorder characterized by electrolyte imbalance in which hypomagnesemia also occurs.
Hungry Bone Syndrome - It is characterized by the aggressive repair of bones following the parathyroidectomy to fix the damaged bones leading to excessive usage of magnesium, causing hypomagnesemia.
Gastric Surgeries - Gastric bypass surgeries would lead to hypomagnesemia due to decreased absorption.
Acute Pancreatitis - It may occur due to the saponification of magnesium in the necrotic fat-causing its deficiency.
Familial Hypomagnesemia with Hypercalciuria and Nephrocalcinosis - This is a rare autosomal recessive disorder characterized by the urinary loss of magnesium and other elements.
Diabetes Mellitus - It occurs due to polyuria (increased or frequent urination) would lead to urinary loss of magnesium.
Hypomagnesemia Due to Certain Medications:
The medications that cause a reduction in magnesium levels include:
Diuretics - Thiazide and Furosemide diuretics cause hypomagnesemia as a result of excessive urination.
Antibiotics - Aminoglycoside antibiotics cause hypomagnesemia by inhibiting the absorption of magnesium in the distal convoluted tubules.
Proton Pump Inhibitors - Hypomagnesemia is reported to be one of the side effects of proton pump inhibitors as they inhibit the absorption of magnesium by the intestine.
Amphotericin B - It impairs kidney function, thereby causing urinary loss of magnesium.
Digitalis - Also known as Digoxin, lowers the magnesium concentration by acting on the sodium-potassium pump.
Chemotherapeutic Drugs - Drugs such as Cyclosporine and Cisplatin are known to cause renal toxicity, thereby damaging the ascending limb of the loop of Henle, affecting the reabsorption of magnesium from the primary urine.
What Is the Pathogenesis of Hypomagnesemia?
Hypomagnesemia may be caused as a result of any of the above-discussed etiologies. Mainly the diseases or conditions affect the kidneys and the gastrointestinal tracts. Magnesium is an important electrolyte, and its function is interrelated with other electrolytes such as sodium, calcium, and potassium. Hence the reduced magnesium levels will produce a serious effect on the body as it would directly affect the balance of other electrolytes. The altered magnesium will affect calcium metabolism by decreasing the generation of cyclic adenosine monophosphate, which is essential for the release of parathyroid hormone.
As the parathyroid hormone is a vital component of calcium homeostasis, this would affect the calcium metabolism, thereby manifesting the features of calcium deficiency. On the other hand, potassium channel efflux is inhibited by magnesium, thereby causing increased renal loss of potassium and developing hypokalemia.
What Are the Symptoms of Hypomagnesemia?
The symptoms include:
Manifestations caused due to the disturbance in other electrolyte and hormone balance as a consequence of hypomagnesemia include:
How Is Hypomagnesemia Diagnosed?
The steps in diagnosis include:
History: A thorough medical, habitual, and drug history is important in diagnosing as well as treatment planning in patients with hypomagnesemia.
Physical Examination: Physical examination would provide an idea about the associated signs and symptoms of the conditions such as Trousseau (when pressure is applied to the upper arm by the inflated sphygmomanometer cuff, carpopedal spasm develops) and Chvostek (on tapping the facial nerve area, there will be twitching of the facial nerves) signs, muscle weakness, cardiac murmurs, asthma, etc.
Serum Magnesium - This would indicate low serum magnesium levels, less than mg/dl.
Serum Calcium - This would show low serum calcium levels, indicating hypocalcemia.
Serum Potassium - This would show low serum potassium levels, indicating hypokalemia.
Parathyroid Hormone Levels - Reduced parathyroid hormone levels indicate hypoparathyroidism.
4-Hour Urinary Magnesium Excretion:
24-hour urinary magnesium excretion would help to differentiate the cause of hypomagnesemia either due to renal or gastrointestinal loss of magnesium.
This would show changes in the ECG pattern such as widening of the QRS complex, prolongation of PR, and peaked T waves.
How Is Hypomagnesia Managed?
Treat the Underlying Conditions: The first and prime goal is to treat the underlying disease or the etiological factor causing the disorder. Any of the above-said medications, if taken by the patient, should be withdrawn immediately.
Dietary Intake of Magnesium: Patients with mild hypomagnesemia can be advised to take foods rich in magnesium like whole grains, beans, nuts, peas, sunflower seeds, green leafy vegetables, etc., to compensate for the deficiency.
Oral Supplements: Magnesium sulfate oral supplements can be given orally based on the patient's stability and the severity of magnesium deficiency.
Parenteral Administration: It is followed in hospitalized patients; in stable patients with normal kidney function, 1 to 2 grams of magnesium can be administered within a time period of 15 minutes. In symptomatic patients with severe deficiency, 1 to 2 grams of magnesium can be given in an hour. In children, the dosage is 25 to 50 mg per kilogram of body weight. Patients in the intensive care unit should be fed with magnesium along with other nutrients.
What Is the Prognosis of Hypomagnesemia?
Hypomagnesemia shows a good prognosis after treatment in patients with corrected underlying disorders as well as the withdrawal of the offending agents causing the disease. The prognosis is found to be moderate to poor in patients with kidney diseases and genetic problems worsening the condition. The utmost care and careful treatment are mandatory in those patients to improve the prognosis.
Hypomagnesemia is a common electrolyte disturbance among hospitalized patients. As its levels and physiological functions are interrelated with other electrolytes of the body. Reduction in the magnesium levels has a direct effect on their level as well, causing further complications. Hypomagnesemia should be treated immediately as soon as it is diagnosed to prevent the advent of other complications.