Hypophosphataemia - Causes and Symptoms

Definition

Hypophosphatemia is defined as the condition in which plasma phosphate levels are less than 2.5 mg / dl.

Phosphate is an essential component of many cellular compounds (eg phospholipids of the cell membrane, nucleic acids and adenosine triphosphate) and plays a key role in numerous metabolic processes. As a result, its levels are strictly regulated.

Serum phosphate levels depend on dietary intake, intestinal absorption, bone turnover, cell turnover and renal tubular function. Homeostasis is maintained primarily by parathyroid hormone (PTH) and vitamin D.

Hypophosphataemia can occur when there is an increase in renal losses, a decrease in the intake or a passage inside the phosphate cells. The most common causes include alcoholism, severe burns, prolonged fasting and prolonged use of diuretics (acetazolamide, thiazides, etc.).

Hypophosphatemia secondary to a reduction in the intake occurs when there is a decrease in the amount of phosphate taken with the diet (infrequent, but may result from severe chronic malnutrition) or intestinal absorption (often secondary to inflammatory states, copious diarrhea or surgery).

Reduced renal phosphate reabsorption occurs under conditions of primary hyperparathyroidism, vitamin D deficiency, renal tubular disease, oncogenic osteomalacia and hyperglycemic states.

Finally, hypophosphatemia can be caused by the passage of phosphate in the intracellular compartment, often superimposed on a chronic deficiency of the same. This condition occurs with the administration of glucose or total parenteral nutrition in malnourished patients (for example, alcoholics or anorexics). The redistribution of phosphates can also result from acute respiratory alkalosis and administration of insulin in the therapy of diabetic ketoacidosis.

The clinical manifestations of hypophosphatemia depend on the severity and duration of low blood phosphate levels. Patients with moderate hypophosphataemia (1.5-2.5 mg / dl) are generally asymptomatic, whereas in severe depletion metabolic encephalopathy, bone pain and symptoms secondary to muscle dysfunction (strength reduction, rhabdomyolysis, cardiomyopathy and respiratory failure) may develop ). Haematological abnormalities may also be present, such as haemolysis secondary to the reduction of ATP, leukocyte dysfunction and thrombocytopenia.