Calcitonin

Thyroid Factor

The Natural Thyroid Diet

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Calcitonin is a 32 amino acid polypeptide, with a disulphide bridge between the cysteine residues in positions 1 and 7. It is secreted by the parafollicular or C cells of the thyroid gland, which comprise 0.1% of the thyroid mass.

The calcitonin receptor is a seven transmembrane domain G-protein-coupled receptor in the osteoclast and in the kidneys. Receptor down-regulation may explain the self-limiting nature of calcitonin action.

Calcitonin inhibits osteoclastic activity by increasing intracellular cyclic AMP levels. It diminishes osteolytic activity of osteoclasts and osteocytes. Other actions include: Antagonism to the effect of PTH on bone; Inhibition of gastric motility and gastrin secretion; Inhibition of jejunal absorption of calcium and phosphate; Inhibition of tubular reabsorption and promotion of urinary excretion of phosphate, calcium and sodium;

Inhibition of renal 1 alpha-hydroxylase activity, with decreased synthesis of calcitriol.

Calcitonin is used for the treatment of hypercalcaemia and for osteoporosis. Salmon calcitonin possesses 100 times the potency of human calcitonin.

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