Causes of high and low magnesium in blood

Hypomagnesemia occurs due to the following reasons.

• Reduced absorption of magnesium in the intestine due to poor nutrition, impaired absorption, prolonged diarrhea. This is the mechanism of hypomagnesemia development in acute and chronic dyspepsia, enterocolitis, ulcerative colitis, acute intestinal obstruction, edematous pancreatitis, alcoholism.
• Increased excretion of magnesium by the kidneys due to hypercalcemia, osmotic diuresis or taking drugs such as loop diuretics, aminoglycosides, cyclosporine. Any damage to the renal tubules leads to increased excretion of magnesium in the urine. Hypomagnesemia develops in about 30% of patients with diabetes mellitus, but in severe forms of the disease it is difficult to detect due to a decrease in the volume of intravascular fluid. Against the background of hypomagnesemia, diabetes mellitus is more severe. The Mg/creatinine ratio in the urine of patients with diabetes mellitus increases proportionally to the severity of the clinical course of the disease.

In clinical practice, magnesium deficiency occurs more often than it is diagnosed (in approximately 10% of inpatients).

Magnesium is one of the regulators of vascular tone, promotes dilation of the vascular wall. Low concentration of extracellular magnesium leads to spasm of blood vessels or increases their sensitivity to pressor agents. Intracellular magnesium content correlates with the value of arterial pressure in patients with arterial hypertension. The action of a number of drugs that reduce arterial pressure is realized through magnesium. A decrease in the magnesium content in the myocardium of those who died from myocardial infarction and in the blood of patients with coronary heart disease has been noted. A sharp drop in the concentration of magnesium in the blood can be one of the causes of sudden death.

Magnesium is a hypolipidemic agent. Hypomagnesemia promotes activation of the atherosclerotic process. Hyperlipidemia against the background of hypomagnesemia promotes progression of fatty infiltration of the liver. Under conditions of hypomagnesemia, the activity of heparin-dependent lipoprotein lipase and lecithin-cholesterol acyltransferase decreases. Impaired LDL clearance under conditions of magnesium deficiency explains the development of hyperlipidemia in diabetes mellitus.

With a magnesium deficiency, platelet aggregation increases and thrombus formation processes are activated, which is why magnesium is considered a natural anticoagulant.

Hypomagnesemia is a common complication of alcoholism and alcohol withdrawal. Hypomagnesemia also accompanies hypophosphatemia (severe hyperparathyroidism and thyrotoxicosis) and cardiac glycoside intoxication.

When evaluating the results of a blood serum magnesium test, one must always remember about “false” hypomagnesemia, which can occur during stress, acute infectious diseases, and hypovolemia.

Hypomagnesemia often causes hypokalemia and hypocalcemia, which are reflected in the clinical picture. Neurological disturbances include drowsiness, confusion, tremor, involuntary muscle contractions, ataxia, nystagmus, tetany, and seizures. The ECG shows prolongation of the PQ and QT intervals. Atrial and ventricular arrhythmias sometimes occur, especially in patients receiving digoxin.

Sometimes severe cardiac arrhythmias can be corrected with magnesium preparations (when administered intravenously), even in cases where traditional antiarrhythmic therapy is ineffective.

It should be emphasized that it is quite difficult to detect magnesium deficiency (as well as its excess) in the body, which is due to its low correlation with the concentration of magnesium in the blood serum.

Hypermagnesemia occurs in renal failure, use of lithium preparations, hypothyroidism, lactic acidosis, hepatitis, neoplasms, use of magnesium preparations against the background of undiagnosed renal failure. Clinical manifestations usually develop when the concentration of magnesium in the blood serum is more than 4 mEq/L. Neuromuscular disorders include areflexia, drowsiness, weakness, paralysis and respiratory failure. Cardiovascular disorders include arterial hypotension, bradycardia, prolongation of the PQ, QRS and QT intervals on the ECG, complete atrioventricular block and asystole. The relationship of clinical disorders with the concentration of magnesium in the blood serum is as follows:

• 5-10 mEq/l - delay in impulse conduction through the cardiac conduction system;
• 10-13 mEq/L - loss of deep tendon reflexes;
• 15 mEq/l - respiratory paralysis;
• more than 25 mEq/L - cardiac arrest in the diastolic phase.

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