Function

The majority of phosphorus in the body is used in the formation of teeth and bone, giving phosphorous a strong correlation with calcium: calcium phosphate is deposited and reabsorbed in bone formation.

The remaining phosphorus is involved in various aspects of metabolism and has an important role in every cell in the body.

  • Through the process of phosphorylation, phosphorus combines with glucose and glycerol to promote their absorption into the intestine.
  • As phospholipids, phosphorous transports fatty acids.
  • Phosphorous is a component of ATP and plays a role in energy metabolism.
  • Phosphorus is also involved in the control of acid-base states in blood.

Absorption and Excretion

Phosphate is absorbed in the jejunum of the small intestine. Absorption is regulated by calcium and the vitamin D hormone 1,23-dihydroxycholecalciferol. When phosphate serum level is low, the kidney is stimulated to produce the vitamin D hormone, which facilitates absorption of phosphorus in the intestine. Phosphorus is excreted through the kidneys based on the level of serum phosphorus.

Phosphorous absorption is good when it is obtained through meat sources. Phytic acid, found in cereal grains, reduces the bioavailability. Many antacids are phosphate-binding and reduce absorption.

Clinical Conditions

Hypophosphatemia, or low serum phosphorus, is seen in intestinal diseases such as sprue and celiac disease, which hinder phosphorus absorption. Bone diseases such as rickets or osteomalacia also upset the calcium/phosphorus ratio. Chronic alcohol intake depletes phosphorus stores in the body. Hyperparathyroidism also results in low serum phosphorus levels due to an excess of parathyroid hormone stimulating renal tubular excretion.

Phosphorous deficiencies, called hypophosphatemia, affect the body in a number of ways, impairing proper growth and causing muscle weakness. In some cases, patients with low serum phosphorous have displayed cardiac arrythmias.

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