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Calcium regulation in the human body. [6]The plasma ionized calcium concentration is regulated within narrow limits (1.3–1.5 mmol/L). This is achieved by both the parafollicular cells of the thyroid gland, and the parathyroid glands constantly sensing (i.e. measuring) the concentration of calcium ions in the blood flowing through them.
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Though calcium is the most plentiful electrolyte in the body, a large percentage of it is used to form the bones. [14] It is mainly absorbed and excreted through the GI system. [ 14 ] The majority of calcium resides extracellularly, and it is crucial for the function of neurons , muscle cells , function of enzymes , and coagulation . [ 14 ]
Hyperparathyroidism is the state in which there is excess parathyroid hormone circulating in the blood. This may cause bone pain and tenderness, due to increased bone resorption. With increased circulating calcium, there may be other symptoms associated with hypercalcemia, most commonly dehydration.
The US Institute of Medicine (IOM) established Recommended Dietary Allowances (RDAs) for calcium in 1997 and updated those values in 2011. [6] See table. The European Food Safety Authority (EFSA) uses the term Population Reference Intake (PRIs) instead of RDAs and sets slightly different numbers: ages 4–10 800 mg, ages 11–17 1150 mg, ages 18–24 1000 mg, and >25 years 950 mg. [10]
Calcium-binding proteins have specific domains that bind to calcium and are known to be heterogeneous. One of the functions of calcium binding proteins is to regulate the amount of free (unbound) Ca 2+ in the cytosol of the cell. [1] The cellular regulation of calcium is known as calcium homeostasis.
Parafollicular cells produce calcitonin in response to high blood calcium. Calcitonin decreases the release of calcium from bone, by decreasing the activity of osteoclasts, cells which break down bone. Bone is constantly reabsorbed by osteoclasts and created by osteoblasts, so calcitonin effectively stimulates movement of calcium into bone.
Procalcitonin (PCT) is a peptide precursor of the hormone calcitonin, the latter being involved with calcium homeostasis. It arises once preprocalcitonin is cleaved by endopeptidase. [1] It was first identified by Leonard J. Deftos and Bernard A. Roos in the 1970s. [2]