Parathyroid hormone
Parathyroid hormone, also called parathormone and PTH is a polypeptide of 84 amino acids. It is secreted by the parathyroid glands. It controls calcium metabolism at three levels, bone, kidney and intestine.
There exists, in addition to parathyroid hormone itself peptides named PTHrP (parathyroid-hormone-related peptide or protein) which activate PTH receptors and have a physiological and pathological role.
The principal difference between PTH and PTHrP is that PTH has an endocrine action: transported by blood it acts remotely of its location of secretion whereas PTHrP acts topically, it has a paracrine action.
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