In this article, we review the roles of calcium and phosphorus, including calcium and phosphorus have an inverse relationship: when calcium levels increase. product of calcium and inorganic phosphorus falls below a certain critical level. evidence of a reciprocal relationship between the Ca and inorganic P of the. Many of the systems that regulate calcium homeostasis also contribute to that of phosphate, albeit sometimes in a reciprocal fashion, and thus will also be.
Parathyroid hormone, vitamin D and the kidneys all help to regulate calcium and phosphorus levels in the blood. Parathyroid hormone, or PTH, and vitamin D work to keep these levels in balance.
Calcium and phosphorus are absorbed into the blood through the small intestine after eating foods that contain these nutrients. The bones will also release the nutrients to help maintain necessary blood levels.
The parathyroid gland can sense an imbalance of calcium or phosphorus. If the calcium level is low, the parathyroid gland will release PTH, which tells the kidneys to produce more active vitamin D.
This helps the body to absorb more dietary calcium and phosphorus through the intestine, tells the bone to release calcium and phosphorus into the blood and tells the kidneys to excrete more phosphorus in the urine.
Calcium, Phosphorus and the Kidneys Healthy kidneys will eliminate excess phosphorus and calcium in the blood.
If kidney function is impaired, the body will not be able to get rid of extra phosphorus. High phosphorus levels stimulate the release of parathyroid hormone, which can cause complications when the normal mechanism for bone mineral management does not work correctly.
A high phosphorus level may also result in a low calcium level. Calcium binds with phosphate and is deposited in the tissue.
The remainder of body phosphate is present in a variety of inorganic and organic compounds distributed within both intracellular and extracellular compartments. Normal blood concentrations of phosphate are very similar to calcium.
Fluxes of Calcium and Phosphate Maintaining constant concentrations of calcium in blood requires frequent adjustments, which can be described as fluxes of calcium between blood and other body compartments. Three organs participate in supplying calcium to blood and removing it from blood when necessary: The small intestine is the site where dietary calcium is absorbed.
Importantly, efficient absorption of calcium in the small intestine is dependent on expression of a calcium-binding protein in epithelial cells. Bone serves as a vast reservoir of calcium. Stimulating net resorption of bone mineral releases calcium and phosphate into blood, and suppressing this effect allows calcium to be deposited in bone.
The kidney is critcally important in calcium homeostasis.Basics of calcium and phosphate homeostasis
Under normal blood calcium concentrations, almost all of the calcium that enters glomerular filtrate is reabsorbed from the tubular system back into blood, which preserves blood calcium levels. If tubular reabsorption of calcium decreases, calcium is lost by excretion into urine.
Hormonal Control Systems Maintaining normal blood calcium and phosphorus concentrations is managed through the concerted action of three hormones that control fluxes of calcium in and out of blood and extracellular fluid: Parathyroid hormone serves to increase blood concentrations of calcium.
The Balance of Calcium & Phosphorus
Mechanistically, parathyroid hormone preserves blood calcium by several major effects: Stimulates production of the biologically-active form of vitamin D within the kidney. Facilitates mobilization of calcium and phosphate from bone. To prevent detrimental increases in phosphate, parathyroid hormone also has a potent effect on the kidney to eliminate phosphate phosphaturic effect.
Maximizes tubular reabsorption of calcium within the kidney. This activity results in minimal losses of calcium in urine. Vitamin D acts also to increase blood concentrations of calcium.
Calcium and Phosphate Homeostasis
It is generated through the activity of parathyroid hormone within the kidney. Far and away the most important effect of vitamin D is to facilitate absorption of calcium from the small intestine. In concert with parathyroid hormone, vitamin D also enhances fluxes of calcium out of bone.