Hyperphosphatemia & Metabolic Acidosis

Your body contains a large amount of phosphate, which is concentrated in your bones and distributed in lesser amounts throughout your organs and tissues. Phosphate is essential for energy production and has many other crucial metabolic and structural functions. Excess blood phosphate, or hyperphosphatemia, occurs with a variety of medical conditions including metabolic acidosis, characterized by increased blood acidity due to metabolic imbalances.

Phosphate Regulation

Your blood phosphate level is tightly controlled via hormonal and metabolic mechanisms. Your intestines, kidneys and bones have primary roles in maintaining a normal blood phosphate level. Your kidneys are principally responsible for preventing hyperphosphatemia by excreting excess amounts into the urine. Metabolic imbalances that increase the acids in your bloodstream, however, can interfere with or overwhelm your kidneys' ability to excrete excess phosphate.

Metabolic Acidosis

Metabolic acidosis occurs when your kidneys fail to excrete acids normally or your cells produce too much acid. Diabetic ketoacidosis is a common cause of metabolic acidosis, which occurs when sugar cannot enter your cells due to reduced production of the hormone insulin. Lack of sugar in your cells causes your body to burn fat, generating acidic chemicals called ketone bodies. Severe diarrhea leading to rapid loss of the alkaline chemical bicarbonate in the stool is another frequent cause of metabolic acidosis. Overproduction of lactic acid, which may occur with cancer, liver or heart failure, shock, seizures and excess alcohol consumption, can also cause metabolic acidosis.

The Phosphate-Acidosis Connection

Phosphate concentrations are higher inside your cells than in your bloodstream. With metabolic acidosis, phosphate molecules from inside your cells move into your blood, causing hyperphosphatemia. In some cases, cell death causes phosphate to spill into your blood, which occurs with certain types of cancer. Alternatively, phosphate may shift into your bloodstream without cell damage.

Diagnosis

Doctors use blood tests to determine whether you have hyperphosphatemia and metabolic acidosis. A phosphorus level greater than approximately 4.1 mg/dL indicates hyperphosphatemia. Acidosis is present if the pH of your blood is less than 7.35. Measurement of other substances in your blood, such as sodium, potassium, chloride, bicarbonate, oxygen, glucose, lactic acid and ketones, helps your doctor determine the underlying cause of metabolic acidosis and hyperphosphatemia.

Treatment

Treatment of metabolic acidosis with hyperphosphatemia focuses on the underlying cause of the problem. If you have diabetic ketoacidosis, for example, administration of insulin to enable glucose delivery to your cells is the primary form of treatment. As the underlying metabolic abnormality resolves, acidosis abates and blood phosphate levels typically return to normal. In severe cases of acidosis, bicarbonate may be administered to help correct your blood pH. With severe hyperphosphatemia, your doctor may treat you with a phosphate-binding medicine such as calcium, magnesium or aluminum salts.