Hypomagnesemia overview

# Overview
Hypomagnesemia is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.7 mmol/l is used as reference. It must be noted that hypomagnesemia is not equal to magnesium deficiency. Hypomagnesemia can be present without magnesium deficiency and vice versa.
It may result from a number of conditions including inadequate intake of magnesium, chronic diarrhea, malabsorption, alcoholism, chronic stress, diuretic use and other disorders.

# Historical Perspective
The prefix hypo- means low (contrast with hyper-, meaning high). The middle magnes refers to magnesium. The end portion of the word, -emia, means 'in the blood' (note, however, that hypomagnesemia is usually indicative of a systemic magnesium deficit).

# Classification

# Pathophysiology
The body contains 22-26 grams of magnesium (1,000 mmols). Of this, 60% is located in bone (30% of which is exchangeable and functions as a reservoir to stabilize the serum concentration), 20% in skeletal muscle,  19% in other soft tissues, 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. Magnesium is a cofactor in more than 300 enzyme regulated reactions. Most importantly forming and using ATP, i.e. kinase. There is a direct effect on sodium- (Na), potassium- (K) and calcium (Ca)channels.

# Causes
Magnesium deficiency is not uncommon in hospitalized patients. Elevated levels of magnesium (hypermagnesemia), however, are nearly always iatrogenic. 10-20% of all hospital patients, and 60-65% of patient in the intensive care unit (ICU) have hypomagnesemia. Hypomagnesiemia is underdiagnosed, as testing for serum magnesium levels is not routine. Hypomagnesemia results in increased mortality. Causes of hypomagnesemia can be Alcoholism, Diuretic use, Antibiotics, stress, Gastrointestinal causes, Diabetes mellitus, Malabsorption, and Acute pancreatitis

# Differentiating Hypomagnesemia from other Diseases
Hypomagnesemia should be differentiated from other causes of abnormal parathyroid hormone levels for example, hypoparathyroidism (genetic and idiopathic), acrodysostosis and pseudohypoparathyroidism.

# Epidemiology and Demographics

# Risk Factors
The following patients have high risk of hypoglycemia development, critically ill patients, hospitalized patients, burned patients, head and neck cancer patients treated with cetuximab

# Screening

# Natural History, Complications and Prognosis
Hypomagnesemia can lead to neuromuscular, neurological, cardiovascular, endocrine, renal, and biochemical manifestations.

# Diagnosis

## Diagnostic Study of Choice

## History and Symptoms
Deficiency of magnesium causes weakness, muscle cramps, cardiac arrhythmia, increased irritability of the nervous system with  tremors, athetosis, jerking, nystagmus and an extensor plantar reflex. In addition, there may be confusion, disorientation, hallucinations, depression, epileptic fits, hypertension, tachycardia and tetany.

## Physical Examination
Signs and symptoms of hypomagnesemia include anything from mild tremors and generalized weakness to cardiac ischemia and death.

## Laboratory Findings
The diagnosis can be made by finding a plasma magnesium concentration of less than 0.7mmol/l. Since most magnesium is intracellular, a body deficit can be present with a normal plasma concentration.
In addition to hypomagnesemia, up to 40% cases will also have hypocalcemia while in up to 60% of cases, hypokalemia will also be present.

## Electrocardiogram
ECG changes are non-specific and include a slight prolongation of conduction (a prolonged QT interva) and the depression of the ST segment. Magnesium depletion increases susceptibility to arrhythmogenic effects of drugs such as isoproterenol and cardiac glycosides and this includes supraventricular and ventricular arrhythmias. Torsade de pointes (repetitive polymorphous ventricular tachycardia with prolongation of QT interval) has been reported in cases of hypomagnesaemia. Torsade de pointes and other arrhythmias have been successfully treated with magnesium. However, this may be a pharmacological effect, independent of underlying magnesium deficiency.

## X-ray

## Echocardiography and Ultrasound

## CT scan

## MRI

## Other Imaging Findings

## Other Diagnostic Studies
Other diagnostic studies can include evaluation for the underlying cause of hypomagnesemia. This requires a thorough investigation for the presence of diabetes mellitus, alcoholism, gastrointestinal conditions involving poor absorption and/or poor nutritional intake, or a family history of hypomagnesemia without or without other electrolyte abnormalities, and a complete list of medications used. The suspected underlying etiology may be confirmed with urinary studies based on its mechanism via renal wasting or extrarenal cause. Patients with hypomagnesemia due to renal Mg2+ wasting have been suggested to present with a fractional excretion of Mg2+ greater than 4%, whereas those with extrarenal causes present with a much lower percentage, typically 2% or less.

# Treatment

## Medical Therapy
Treatment of hypomagnesemia depends on the degree of deficiency and the clinical effects. Oral replacement is appropriate for patients with mild symptoms, while intravenous replacement is indicated for patients with severe clinical effects.

## Surgery

## Primary Prevention
There are no established measures for the primary prevention of hypomagnesemia

## Secondary Prevention
There are no established measures for the secondary prevention of hypomagnesemia.