Phosphorus is an essential dietary nutrient that is concentrated in your bones and cells. Your kidneys are the primary regulators of phosphorus balance in your body but many medical conditions can affect your phosphorus level. Abnormally high or low levels may cause serious metabolic problems.
Phosphorus circulates in your bloodstream in the form of phosphate, or PO4, which is the substance measured in the laboratory when your phosphorus level is checked. Although the terms phosphorus and phosphate are not technically synonymous, they are commonly used interchangeably. The normal range for phosphate among adults is approximately 2.4 to 4.1 milligrams per deciliter of blood; the normal range may vary somewhat from one clinical laboratory to another. A low blood phosphate level is known as hypophosphatemia; an elevated level is termed hyperphosphatemia.
Diet and Absorption
Your phosphorus level may fall if your dietary intake is inadequate or there is interference with intestinal phosphorus absorption. Because many foods contain phosphorus, dietary insufficiency is uncommon unless you are severely malnourished. Persistent vomiting and diarrhea may interfere with phosphorus absorption, potentially leading to a deficiency. Aluminum binds phosphorus in your digestive system, preventing its absorption, so frequent use of aluminum-containing antacids may also cause a deficiency.
Vitamin D facilitates intestinal absorption of phosphorus and calcium and it also promotes the conservation of phosphorus in your kidneys, preventing excess loss in the urine. If you have a vitamin D deficiency, a secondary phosphorus deficiency may occur. Conversely, if you ingest too much vitamin D, you may develop hyperphosphatemia.
Your kidneys normally rid your body of excess dietary phosphorus. Any kidney disease that significantly interferes with urinary phosphorus excretion can lead to hyperphosphatemia. If you have had a kidney transplant, the medications you take to prevent rejection of the donor organ may cause excess urinary phosphorus loss, potentially leading to a deficiency.
Parathyroid Hormone Imbalance
Your parathyroid glands are tiny endocrine organs situated behind your thyroid. They produce parathyroid hormone, or PTH, which acts on your bones and kidneys to increase your blood calcium level. Calcium and phosphorus metabolism are closely intertwined with a yin-yang relationship. As your calcium level increases in response to PTH, your phosphorus level decreases. Overproduction of PTH, or hyperparathyroidism, typically causes an abnormally low phosphorus level. Conversely, low PTH production, or hypoparathyroidism, leads to an elevated phosphorus level.
The acidity or alkalinity of your blood affects your phosphorus level. Medical conditions that cause your blood to be too acidic can lead to hyperphosphatemia. If your blood becomes too alkaline, your phosphorus level may fall to an abnormally low level.
- Oregon State University Linus Pauling Institute: Phosphorus
- Tietz Textbook of Clinical Chemistry: Carl A. Buris, Ph.D., Edward R. Ashwood, M.D.
- MedlinePlus: Serum Phosphorus
- Atlas of Diseases of the Kidney: Disorders of Phosphate Balance
- Clinical Laboratory Medicine: Kenneth D. McClatchey, M.D.
- EndocrineWeb: Your Parathyroid Glands