n. a peptide (so-called because of its C shape) formed when insulin is produced from its precursor molecule, proinsulin. It is secreted in equal molar amounts to insulin. However, as it remains detectable in the plasma much longer than insulin it can be more easily assayed as a marker of the degree of insulin secretion. This can be useful to assess the ability of the pancreas to secrete insulin, for example when trying to determine whether somebody has type 1 or type 2 diabetes or to distinguish an insulin-secreting tumour (an *insulinoma) from surreptitious insulin usage in somebody presenting with unexplained hypoglycaemia.
The atria (see ATRIUM) of the heart contain peptides with potent diuretic and vasodilating properties. It has been known since 1980 that extracts of human atria have potent diuretic and natriuretic effects in animals (see DIURETICS). In 1984 three polypeptide species were isolated from human atria and were called alpha, beta and gamma human atrial natriuretic peptides. Plasma concentration of immunoreactive atrial natriuretic peptide can now be measured: the levels are low in healthy subjects and are increased in patients with congestive heart failure. Infusion of the peptides reduces blood pressure and causes a natriuresis and diuresis.... atrial natriuretic peptide
(GLP-1) a hormone – an *incretin – that is produced in the small intestine. GLP-1 has a half-life in the blood circulation of less than two minutes due to rapid breakdown by the enzyme dipeptidyl peptidase-IV (DPP-IV). It is a potent antihyperglycaemic hormone, stimulating the release of insulin from the pancreatic beta cells in response to a rising blood glucose level after eating. This glucose-sensitive action also allows the effect of GLP-1 on the beta cells to switch off when the blood glucose level comes down to the normal baseline between meals. Thus the *GLP-1 receptor agonist group of drugs, used in type 2 diabetes, can restrict the rise in blood glucose level after meals but have a low risk of causing subsequent *hypoglycaemia.... glucagon-like peptide-1
any of several peptides that stimulate diuresis (increased urine production) and vasodilatation (widening of blood vessels). They act on the kidney tubules to promote excretion of sodium (natriuresis) and water. Atrial natriuretic peptide (ANP) is produced in the atria of the heart in response to a rise in atrial pressure. Brain natriuretic peptide (BNP) is produced in the brain and the ventricles of the heart, mainly in response to stretching of the ventricular muscle (as occurs in congestive heart failure). Measurement of blood levels of BNP can be used as a diagnostic test for heart failure and also as an indicator of prognosis.... natriuretic peptide
(PRRT) a type of radiotherapy used to treat neuroendocrine tumours (NETs; see neuroendocrine system). A *radionuclide is combined with a relevant *peptide to create a so-called radiopeptide, which is injected into the patient’s bloodstream. Because NETs have an overexpression of peptide receptors, the radiopeptide binds to the tumour, delivering a high dose of radiation directly to the cancer cells. The chief merit of PRRT is this ability to target delivery of radionuclides for highly localized treatment. A similar technique, using a gamma emitter as the radionuclide, can be used for locating and imaging NETs.... peptide receptor radionuclide therapy
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