FGF23, or Fibroblast Growth Factor 23, is a protein produced mainly by bone cells. It plays a crucial role in regulating phosphate and vitamin D levels in the body. By controlling how much phosphate is reabsorbed in the kidneys, FGF23 helps maintain proper mineral balance, which is essential for bone health. Elevated levels of FGF23 can indicate certain health conditions, such as chronic kidney disease or X-linked hypophosphatemia, a genetic disorder. Understanding FGF23 is important for diagnosing and managing these conditions, as it can influence treatment decisions related to mineral and bone disorders.