Lastly, parathyroid hormone increases calcium reabsorption and reduces the reabsorption of phosphate from the kidneys, so more phosphate is excreted through the urine.
This can result in conditions like primary hyperparathyroidism which result in too much parathyroid hormone, which leads to excess phosphate being excreted in the urine.
Because most of phosphate is locked up with calcium in the bones, the levels of phosphate are heavily tied with the levels of ionized calcium in the body.
This causes a demand for phosphate in cells because the first step in glucose metabolism is to have the enzyme hexokinase attach phosphate to the glucose.