Background
Magnesium is one of the body's major electrolytes. As the second most common intracellular cation, it plays a vital role in many cellular metabolic pathways. [1] Magnesium is required for deoxyribonucleic acid (DNA) and protein synthesis. It is a necessary cofactor for most enzymes in phosphorylation reactions. It is also important for parathyroid hormone synthesis.
The total body content of this central cation is 2000 mEq, or 24 g. The magnesium is distributed in bone (67%), intracellularly (31%), and extracellularly (a mere 1%). [2] The intracellular concentration is 40 mEq/L, while the normal serum concentration is 1.5-2.0 mEq/L. Of this serum component, 25-30% is protein bound, 10-15% is complexed, and the remaining 50-60% is ionized.
Magnesium is absorbed in the ileum and excreted in stool and urine. The minimum daily requirement of magnesium is 300-350 mg, or 15 mmol; this amount is easily obtainable with a normal daily intake of fruits, seeds, and vegetables because magnesium is a component of chlorophyll and is present in high concentrations in all green plants.
The kidney is the main regulator of magnesium concentrations. Absorption occurs primarily in the proximal tubule and thick ascending limb of the loop of Henle.
Hypermagnesemia is a rare electrolyte abnormality because the kidney is very effective in excreting excess magnesium. [3]
Pathophysiology
Magnesium excess affects the CNS, neuromuscular, and cardiac organ systems. It most commonly is observed in renal insufficiency and in patients receiving intravenous (IV) magnesium for treatment of a medical condition. [4]
Epidemiology
Frequency
United States
Hypermagnesemia occurs only rarely in the United States.
Prognosis
A study by Haider et al that screened 5,339 patients with plasma magnesium concentrations reported that 36.9% of the 151 patients with hypermagnesemia died and that hypermagnesemia was a strong independent risk factor for mortality. [5]
