Hypophosphatemia refers to low phosphate levels in the blood. Symptoms include fatigue and paleness of the skin from anemia, confusion, damage to the heart and muscle weakness. Treatment is aimed at replacing the phosphate and treating the underlying condition that caused the low phosphate levels in the first place. Causes include inadequate absorption or loss through the gut, loss through the urinary tract, and redistribution to compartments in the body outside of the blood.
Malabsorption
Phosphate is derived from the diet. If not enough phosphate is ingested or there are problems digesting and absorbing phosphate, then low phosphate levels will result. Antacids containing magnesium or aluminum bind to phosphate in the gut making it unavailable to be absorbed. Chronic diarrhea causes the loss of water and nutrients, including phosphate. (See References 1 and 2)
Phosphaturia
Phosphaturia refers to excessive phosphate in the urine. People with overactive parathyroid glands excrete too much phosphate into the urine through the kidneys. Fanconi syndrome is a problem in the kidney tubules in which substance such as phosphate are excessively excreted into the urine. Some other rare syndromes, typically from genetic mutations, cause dysfunction of the transporters of phosphate in the kidney. In addition, certain diuretics, or water pills that increase urination, can cause the loss of phosphate. (See References 2 and 3)
Redistribution
Redistribution occurs from two main causes: refeeding syndrome and respiratory alkalosis. If a person is in a starving state, such as anorexics or alcoholics, and then fed, their bodies react by releasing excessive amounts of insulin from the pancreas. Insulin signals cells to take up nutrients from the blood. Excessive insulin drops the levels of phosphate by redistributing it from the blood to the inside of cells.
Fluids such as blood can be acidic, neutral or basic. "Basic" can be thought of as the opposite of acidic. Respiratory alkalosis refers to blood that is basic because of a fast pattern of breathing. This change in blood stimulates an enzyme called phosphofructokinase to attach phosphates to sugar, causing the depletion of available phosphate. The condition also causes increased uptake of phosphate by muscle. (See Reference 2)
