Hypomagnesemia

Introduction When magnesium is <0.75mmol/L, it is called magnesium deficiency, also called hypomagnesemia. Magnesium is one of the essential elements of the human body. The content of magnesium in the cations of the cells is second only to potassium. Magnesium is widely present in various tissues in the body, and participates in many biological processes, and has the function of maintaining muscle contractility and nerve stress. It can activate many enzymes in the body and promote energy metabolism. The normal concentration of serum magnesium is 0.80~1.20mmol/L. The regulation is mainly done by the kidneys. The magnesium excretion of the kidneys is similar to that of potassium. Even if the serum magnesium concentration is lowered, the magnesium excretion of the kidneys does not stop. In many diseases, magnesium metabolism abnormalities often occur.

Cause

1. Excessive loss of digestive tract: due to magnesium absorption in the small intestine and part of the colon, when severe diarrhea, steatorrhea, malabsorption, intestinal fistula, major small bowel resection, etc. can cause hypomagnesemia.

2. Excessive kidney loss: such as chronic pyelonephritis, renal tubular acidosis, acute renal failure during the polyuria period, or long-term use of loop diuretics, thiazides and osmotic diuretics to cause renal loss of magnesium and low magnesium Blood.

3. Insufficient supplementation: Insufficient magnesium in malnutrition, nutritional support solution for certain diseases, or long-term treatment with magnesium-free solution.

4. Patients with hyperthyroidism often have low blood magnesium and negative nitrogen balance, and primary hyperparathyroidism can cause symptomatic magnesium deficiency.

an examination

Related inspection

Urinary hydroxyproline urinary hydroxyproline (HYP) serum chromium (Cr)

1. Determination of serum magnesium

Hypomagnesemia can be diagnosed when serum magnesium is <0.75mmol / L. However, it cannot be used as a reliable indicator of magnesium deficiency in the signal transduction of anti-cardiomyocytes. In addition, blood magnesium is also affected by pH proteins and a variety of factors.

2. Determination of urinary magnesium

If clinically estimated that there is magnesium deficiency and normal blood magnesium, urine magnesium should be measured, 24h urine magnesium output less than 1.5mmol can be diagnosed as magnesium deficiency.

3. Determination of intracellular magnesium in tissues

It can measure magnesium in red blood cells and magnesium in muscle. The latter reflects the change of magnesium in the body more accurately than the former, but the inspection method is complicated.

Differential diagnosis

(a) intestinal malabsorption

The symptoms of primary disease are obviously easy to diagnose, often caused by a combination of factors. In addition to low blood magnesium, intestinal absorption disorders are often accompanied by hypokalemia, low calcium, low sodium, low chlorine, low phosphorus and metabolic wine poisoning.

(two) kidney disease

Hypomagnesemia is mainly seen in kidney diseases with decreased renal tubular reabsorption. Magnesium loss is increased due to polyuria, and there is a positive correlation between urinary magnesium and urine sodium.

(three) hyperthyroidism

Patients with low blood magnesium are often associated with a negative nitrogen balance, which is associated with increased metabolism. As the intracellular metabolism is enhanced, the intracellular magnesium content can be increased, and the urinary magnesium excretion is also increased.

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