HypophosphatemiaE83.38

Serum phosphate concentration < 2.5 mg/dl (0.81 mmol/l). Causes include alcoholism, burns, starvation, and use of diuretics. The clinical symptoms are muscle weakness, respiratory failure, heart failure, seizures, and coma. Diagnosis is made by determining the serum phosphate concentration. Therapy consists of phosphate replacement.

Clinically relevant acute hypophosphatemia occurs in only a few clinical conditions, such as:

• In the recovery phase of diabetic ketoacidosis.
• In acute alcoholism
• In severe burns
• Total parenteral nutrition
• Return to normal nutrition after prolonged malnutrition
• In severe respiratory alkalosis
• Acute severe hypophosphatemia with a serum phosphate < 1 mg/dl (< 0.32 mmol/l) is usually caused by transcellular phosphate shifts in the presence of pre-existing chronic phosphate deficiency.

Chronic hypophosphatemia is usually the result of decreased renal phosphate reabsorption. Causes include:

• Elevated parathyroid hormone levels, as in primary and secondary hyperparathyroidism.
• Other hormonal disorders, such as Cushing's syndrome and hypothyroidism
• Vitamin D deficiency
• Electrolyte disorders, such as hypomagnesemia and hypokalemia
• Theophylline intoxication
• Prolonged diuretic therapy

Severe chronic hypophosphatemia results from a prolonged negative phosphate balance. Causes include:

• Chronic starvation or malabsorption, often in patients with alcoholism, especially in combination with vomiting or severe diarrhea.
• Prolonged ingestion of large amounts of phosphate-binding aluminum, usually in the form of antacids.
• Patients with advanced chronic kidney disease (especially those on dialysis) often take phosphate binders with meals to reduce dietary phosphate intake. This can lead to hypophosphatemia with prolonged use.

Mostly asymptomatic.

Clinical symptoms appear only at levels <0.5mmol/l. Clinical signs are: anorexia, muscle weakness and osteomalacia.

Furthermore:

• Neurological disorders such as progressive encephalopathy with convulsions, coma and death. Muscle weakness in severe hypophosphatemia may be accompanied by rhabdomyolysis, especially in alcoholism.
• Hematologic disorders: hemolytic anemia, decreased oxygen delivery of hemoglobin, and impaired leukocyte and platelet function.

Serum phosphate concentration < 2.5 mg/dl (< 0.81 mmol/l).

Hypophosphatemia occurs in 2% of all hospitalized patients but has an increased prevalence in certain populations (e.g., up to 10% of all hospitalized alcoholics have hypophosphatemia).