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Calcitonin is a 32 amino acid peptide hormone secreted by parafollicular cells (also known as C cells) of the thyroid (or endostyle) in humans and other chordates [5] in the ultimopharyngeal body. [6] It acts to reduce blood calcium (Ca 2+), opposing the effects of parathyroid hormone (PTH). [7]
Calcitonin is a hormone secreted by the thyroid in humans. Calcitonin decreases osteoclast activity, and decreases the formation of new osteoclasts, resulting in decreased resorption. [4] Calcitonin has a greater effect in young children than in adults, and plays a smaller role in bone remodeling than PTH. [4]
PTHrP acts similarly to parathyroid hormone in that it binds to the parathyroid hormone 1 receptors on the kidneys and bones and causes an increased tubular reabsorption of calcium and activation of osteoclast activity, respectively. [22] Osteoclasts are a type of bone cell which cause bone resorption, releasing calcium into the bloodstream.
An osteoclast is a large multinucleated cell and human osteoclasts on bone typically have four nuclei [5] and are 150–200 μm in diameter. When osteoclast-inducing cytokines are used to convert macrophages to osteoclasts, very large cells that may reach 100 μm in diameter occur. These may have dozens of nuclei, and typically express major ...
The role of calcitonin, a hormone generated by the thyroid that increases bone deposition, is less clear and probably not as significant as that of PTH. [36] The activation of osteoclasts is regulated by various molecular signals, of which RANKL (receptor activator of nuclear factor kappa-B ligand) is one of the best-studied. [100]
The calcitonin receptor (CT) is a G protein-coupled receptor that binds the peptide hormone calcitonin and is involved in maintenance of calcium homeostasis, [5] particularly with respect to bone formation and metabolism. [6] [7] [8]
Bisphosphonate molecules then attach to and enter osteoclasts where they disrupt intracellular enzymatic functions needed for bone resorption. [38] There are two classes of bisphosphonate compounds: non-nitrogenous (no nitrogen in R 2) and nitrogenous (R 2 contains nitrogen). The two types of bisphosphonates work differently in inhibiting ...
The plasma total calcium concentration is in the range of 2.2–2.6 mmol/L (9–10.5 mg/dL), and the normal ionized calcium is 1.3–1.5 mmol/L (4.5–5.6 mg/dL). [4] The amount of total calcium in the blood varies with the level of plasma albumin, the most abundant protein in plasma, and therefore the main carrier of protein-bound calcium in the blood.