Excerpt
The kidneys control phosphorus—an essential electrolyte needed for homeostasis. Phosphorus and calcium have an inverse relationship. Normally, when phosphorus levels are elevated, calcium levels are decreased. However, when the kidneys don't function, phosphorus can't be excreted, leading to elevated phosphorus levels. The calcium level is decreased because of the lack of vitamin D activation by the failed kidney. As a result, calcium absorption is decreased, leading to low calcium levels.
The main source of phosphorus intake is through the diet, including dairy products, nuts, seeds, and beans. Many high-phosphorus foods are difficult to avoid because phosphorus is used in a variety of processed foods. Generally, 60% to 70% of phosphorus absorption takes place in the gastrointestinal (GI) tract. An elevated phosphorus level is referred to as hyperphosphatemia. Normal phosphate levels are 3.0 to 4.5 mg/dL; in ESRD, target phosphorus levels are 3.5 to 5.5 mg/dL.
In order to decrease the risk of complications associated with hyperphosphatemia, phosphorus levels are managed using phosphate binders. Let's take a closer look.