The need to evaluate serum phosphorus frequently results from alterations in serum calcium concentrations. Calcium and phosphorus work together in the body in a complementary manner. Phosphorus is excreted in the urine, with increases or decreases reflecting the opposite in calcium levels. Phosphorus level testing might help determine renal, endocrine, calcium and skeletal conditions. High phosphorus levels usually result from problems with excretion as opposed to diet or intestinal absorption.
High Phosphorus Levels
Most of the body's phosphorus is stored in the bones and aids in bone formation. High levels can be the result of parathyroid gland disorders, kidney failure and increased oral intake with supplements. In addition, healing bone fractures, gastrointestinal obstructions and skeletal diseases also elevate phosphorus levels. Increased phosphorus levels might cause calcium phosphate deposits in the body's tissues that damage organs, especially the kidneys. High phosphorus concentrations decrease the conversion of vitamin D to its active form, called calcitriol, in the kidneys, which lowers blood calcium.
Test Preparation
Testing for a serum phosphorus level requires a blood sample, but there is no restriction of food or fluids before the test. A number of factors elevate phosphorus test results, including anabolic steroids, androgen hormones and damage to the red blood cells in the sample called hemolysis. For those with kidney failure or poorly functioning parathyroid glands, increased dietary phosphorus can raise serum phosphorus levels. Higher phosphorus concentrations also occur with children as a result of continuous bone growth and are considered normal.
Phosphorus Function
Phosphorus, a primary part of bones, combines with calcium to form hydroxyapatite, a calcium phosphate salt. Phosphorus is also an important part of the cell wall membranes, energy production in the body, enzyme and hormone formation, as well as storing and transferring genetic information. The ability of red blood cells to transport oxygen to the body's tissues is influenced by phosphorus. Phosphorus also acts as an intermediary to help preserve the acid-base equilibrium in the body.
Additional Considerations
Phosphorus is available in a variety of foods including meats, vegetables, baking ingredients, fast foods, fish, desserts, milk and milk products. Soft drinks, processed and packaged snack foods are high in phosphorus and might cause a hazard to bone health when used as a replacement for foods high in calcium. Frequently, moderate phosphorus abnormalities are asymptomatic, but when symptoms do occur they reflect calcium abnormalities such as weakness, muscle cramps, kidney problems and intestinal disorders. Testing for, or evaluating, these symptoms help your physician determine what treatment may be successful.
