Glucagon gastrin and

The regulation of calcitonin synthesis and release from the parafollicular C cells of the thyroid gland is calcium dependent. Rising serum calcium is the principal stimulus responsible for calcitonin synthesis and release. Other hormones, such as glucagon, gastrin, and serotonin, also stimulate calcitonin release. Calcitonin has been isolated in tissues other than the parafollicular C cells (parathyroid, pancreas, thymus, adrenal), but it is not known whether this material is biologically active. 

Somatostatin is a cyclic tetradecapeptide hormone, characterized as the major physiological inhibitor of growth hormone released from the pituitary, but inhibits the release of many other physiologically important compounds, including insulin, glucagon, gastrin, and secretin (Wolkowitz, 1994). 

Somatotropin release inhibiting hormone (SIH), somatostatin a polypeptide, M, 1638, which inhibits secretion of somatotropin, thyrotropin, insulin, glucagon, gastrin and cholecystokinin. SIH has a broad activity spectrum it acts outside the hypothalamus as a neurotransmitter in the central nervous system, and as a hormone in the intestinal tract it has also been found in the thyroid and pancreas. 

Somatostatin, a 14-amino-acid peptide (Figure 37-2), is found in the hypothalamus, other parts of the central nervous system, the pancreas, and other sites in the gastrointestinal tract. It inhibits the release of GH, glucagon, insulin, and gastrin. 

Know the action of hormones involved in the digestion and metabolism of food substances insulin, glucagon, secretin, gastrin, and cholecystokinin. Know their chemical and physiologic properties and what controls their blood levels. 

Secretin is a 27-amino-aeid polypeptide that is slruciurally. similar to glucagon. The presence of acid in the. small intestine is the most important physiological stimulus for the secretion of secretin. The primary action of secretin Ls on pancreatic acinar cells that regulate the secretion of water and bicarbonate. Secretin also promotes the secretion of pancreatic enzymes, to a lesser extent. Secretin inhibits the release of gastrin and. therefore. ga.slric acid. It also increases stomach-emptying time by reducing the conlraction of the pyloric sphincter. ... 

Octreotide is a long-acting somatostatin analog that inhibits the secretion of serotonin, vasoactive intestinal peptide, gastrin, motilin, insulin, glucagons, secretin, and pancreatic polypeptide. It is used for the control of symptoms in patients with carcinoid and vasoactive intestinal peptide-secreting tumors (VIPomas). Its major toxicity is nausea and vomiting. 

Studies have shown that, in addition to the conventional peptide hormones of pancreatic islets (insulin, glucagon, somatostatin, and pancreatic polypeptide), these tumors can also secrete (and express) ectopic peptides, in particular gastrin and VIP (vasoactive intestinal peptide),but on occasion also ACTH (adrenal corticotropic hormone),antidiuretic hormone (ADH), MSH (melanocyte-stimulating hormone), calcitonin, neurotensin, secretoneurin, 754-356 PTH (parathyroid hormone-like peptide),growth hormone and growth hormone releasing factor, secretogranin inhibin/activin, i prohormone... 

They can express any of the pancreatic hormones, as well as ectopic peptides. In some cases, there is more than one hormone expressed. If an IHC "hormone panel" is to be used, the six hormones cover the vast majority of the cases insulin, glucagon, somatostatin, PP, gastrin, and VIP however, hormone IHC in the tumor does not necessarily correlate with the "functionality" status in all cases. Discrepancies do occur, and therefore serology and symptomatology are more reliable in classification of "functionality" status. 

Calcitonin, a polypeptide consisting of 32 amino acids, is produced by parafollicular cells (C cells) of the thyroid gland. The secretion of calcitonin is stimulated by calcium, catecholamine, and theophylline (increased cyclic adenosine monophosphate levels), glucagon, cholecystokinin, gastrin, and cerulean. 

Octreotide acetate is an endocrine and metabolic agent, whose actions mimic those of natural hormone somatostatin. It suppresses secretion of serotonin and gastroentero-pancreatic peptides (e.g., gastrin, insulin, glucagon, secretin, and motilin), and also suppresses the growth hormone. It is indicated in the symptomatic treatment of diarrhea associated with carcinoid tumors, treatment of profuse watery diarrhea associated with vasoactive intestinal peptide tumors (VIPoma), and to reduce blood levels of growth hormone and IGF-1 in acromegaly patients who have had inadequate response to or cannot be treated with resection, pituitary irradiation, and bromocriptine at maximally tolerated doses. 

Calcitonin is secreted continuously under conditions of normocalcemia, and the synthesis of calcitonin is increased when the calcium concentrations in plasma and intracellular fluids increase. Hypermagnesemia has a similar effect on calcitonin production. In hypocalcemia, the production of calcitonin falls. The gastrointestinal hormones—gastrin, glucagon, cholecystokinin, and secretin—and high dietary calcium also stimulate calcitonin production. Long-term hypercalcemia may cause hyperplasia of the C cells. 

P. occur widely and have many different biological functions. Many are hormones, e.g. Corticotropin, Melanotropin, Oxytodn, Vasopressin, Releasing hormones, Insulin, Glucagon, Gastrin, Secretin, Angiotensin, Bradykinin, Endorphins, Opioid peptides (see entries for each of these). Many microorganisms produce P., often with antibiotic activity (see Peptide antibiotics). Some P. are very toxic, e.g. Phallotoxins (see), Amatoxins (see) and Melittin (see). Very simple P. are... 

The conversion of proinsulin to insulin raises a number of intriguing questions. First, is this phenomenon unique Second, why does the structural gene code for an inactive protein The phenomenon is certainly not unique although all details of structure and conversion of the prohormone into hormone are not known. Prohormones of vasopressin, parathormone, gastrin, glucagon, MSH and ACTH have been known to exist. In the case of insulinoma and parathormone adenoma the tumors may secrete large amounts of the extended hormones that appear in the blood and may serve as a diagnostic tool [196]. 

Activation of adenyl cyclase has been implicated in the mechanism of action of various transmitters, such as adrenaline, noradrenaline, serotonine, histamine, polypeptide hormones (TSH, ACTH, LH, MSH. vasopressin, parathyroid hormone, glucagon, gastrine, etc.) and also other hormones such as FSH releasing... 

The scope of applicability of radioimmunoassay is rapidly expanding with the dawn of each day as RIA is being developed for newer pharmaceutical substances. It has attained wide recognition and application both in vitro and in vivo measurements of compounds of interest like insulin, gastrin, glucagon, and growth hormones on one hand whereas drugs like ... 

It inhibits the secretion of numerous hormones and transmitters, including gastrin, cholecystokinin, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide, vasoactive intestinal peptide, and 5-HT. 

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