Gastrointestinal Hormones and Gastrinoma Quiz
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What is a common characteristic of gastrinomas at the time of diagnosis?

  • They are usually localized and non-metastatic.
  • They often present with hyperplasia of G cells.
  • They are often metastatic at presentation. (correct)
  • They have a long median survival outcome.

    • What is the primary function of secretin in the digestive system?

  • Increasing bicarbonate secretion to neutralize gastric acid. (correct)
  • Promoting bile secretion from the gallbladder.
  • Releasing pancreatic enzymes.
  • Stimulating gastric acid secretion.

    • Which of the following best describes the role of cholecystokinin (CCK) in digestion?

  • Increases gastric pH through bicarbonate production.
  • Stimulates gastric motility and secretion.
  • Inhibits the secretion of motilin.
  • Promotes gallbladder contraction and release of pancreatic enzymes. (correct)

    • What is a significant pharmacological treatment approach for elevated gastrin levels?

    <p>Use of somatostatin analogs.</p> Signup and view all the answers

    What effect does somatostatin have on digestive hormone secretion?

    <p>Inhibits the secretion of various digestive hormones.</p> Signup and view all the answers

    What is the primary function of secretin in the small intestine?

    <p>Increases HCO3- secretion by pancreatic duct cells</p> Signup and view all the answers

    What is the primary diagnostic factor for gastrinomas?

    <p>Elevated serum gastrin levels</p> Signup and view all the answers

    Which treatment option is commonly used to manage gastrinomas?

    <p>High dose proton pump inhibitors</p> Signup and view all the answers

    What is the primary function of secretin in the digestive system?

    <p>Stimulates pancreatic bicarbonate secretion</p> Signup and view all the answers

    What triggers the release of cholecystokinin?

    <p>Fatty acids and monoglycerides</p> Signup and view all the answers

    What role does cholecystokinin play in digestion?

    <p>Promoting bile release from the gallbladder</p> Signup and view all the answers

    How does somatostatin affect gastrointestinal hormones?

    <p>Inhibits most GI hormones</p> Signup and view all the answers

    In patients with pernicious anemia, what is a typical finding related to gastrin levels?

    <p>Elevated gastrin levels</p> Signup and view all the answers

    Which is a common pharmacological treatment for gastrinomas?

    <p>Octreotide</p> Signup and view all the answers

    What is the effect of somatostatin on gastric acid secretion?

    <p>It inhibits gastric acid secretion</p> Signup and view all the answers

    What is the purpose of performing a HIDA scan in patients with RUQ pain?

    <p>To evaluate gall bladder function</p> Signup and view all the answers

    Somatostatin is released in response to which of the following conditions?

    <p>Low pH levels (high gastric acidity)</p> Signup and view all the answers

    What effect does secretin have on gastric H+ secretion?

    <p>It inhibits gastric H+ secretion</p> Signup and view all the answers

    What condition is associated with elevated levels of vasoactive intestinal peptide (VIP)?

    <p>VIPoma</p> Signup and view all the answers

    Which hormone is released by I cells and influences pancreatic function?

    <p>Cholecystokinin</p> Signup and view all the answers

    What gastrointestinal dysfunction is most commonly caused by VIP secretion?

    <p>Watery diarrhea</p> Signup and view all the answers

    What is the role of motilin in the digestive system?

    <p>Motilin promotes gastrointestinal motility, particularly during the fasting state.</p> Signup and view all the answers

    How does erythromycin interact with motilin in the treatment of gastroparesis?

    <p>Erythromycin binds to motilin receptors, enhancing gastric motility.</p> Signup and view all the answers

    What triggers the release of gastrin in the gastric phase of digestion?

    <p>Gastrin is released in response to gastric distention and the presence of amino acids and H+ ions.</p> Signup and view all the answers

    Describe the main actions of secretin in the digestive process.

    <p>Secretin primarily stimulates bicarbonate secretion from the pancreas and regulates gastric acid secretion.</p> Signup and view all the answers

    What is the pattern of hormone release during the intestinal phase of digestion?

    <p>During the intestinal phase, gastrin, GIP, and CCK are released in response to nutrients in the small intestine.</p> Signup and view all the answers

    What is the primary physiological action of gastrin on parietal cells?

    <p>It stimulates H+ secretion.</p> Signup and view all the answers

    What type of cells mediate the effects of gastrin?

    <p>Enterochromaffin-like cells (ECL cells).</p> Signup and view all the answers

    Name two stimuli that trigger the release of gastrin.

    <p>Stomach distention and amino acids (especially phenylalanine and tryptophan).</p> Signup and view all the answers

    How does low pH affect gastrin secretion?

    <p>It inhibits gastrin secretion.</p> Signup and view all the answers

    What is a common complication of gastrin secreting tumors such as gastrinomas?

    <p>Chronic diarrhea.</p> Signup and view all the answers

    What distinguishes gastrinomas from normal G cells in terms of response to secretin?

    <p>Gastrinomas are stimulated by secretin, while normal G cells are inhibited by it.</p> Signup and view all the answers

    What is the fasting serum gastrin level indicative of gastrinomas?

    <p>Greater than 10 times the upper limit of normal.</p> Signup and view all the answers

    Which gastrointestinal condition is often refractory to proton pump inhibitor therapy?

    <p>Peptic ulcers associated with gastrinomas.</p> Signup and view all the answers

    What is the key clinical use of secretin regarding gastrinomas?

    <p>The key clinical use of secretin is in the secretin stimulation test, which increases gastrin production in gastrinoma cells.</p> Signup and view all the answers

    What stimuli primarily trigger the release of cholecystokinin?

    <p>Cholecystokinin is primarily stimulated by the presence of fatty acids, monoglycerides, amino acids, and small proteins.</p> Signup and view all the answers

    How does somatostatin influence gastrin release?

    <p>Somatostatin inhibits gastrin release, lowering gastric acid secretion and impacting overall digestion.</p> Signup and view all the answers

    What finding is typically observed in patients with pernicious anemia related to gastrin?

    <p>In pernicious anemia, high gastrin levels and G-cell hyperplasia are typical findings.</p> Signup and view all the answers

    What is the role of secretin in the digestive process?

    <p>Secretin raises pH in the small intestine by increasing HCO3- secretion and inhibiting gastric H+ secretion.</p> Signup and view all the answers

    Describe the effect of high doses of proton pump inhibitors on patients with gastrinomas.

    <p>High doses of proton pump inhibitors, like omeprazole, reduce gastric acid secretion and hence decrease gastrin levels.</p> Signup and view all the answers

    What diagnostic purpose does a HIDA scan serve in evaluating RUQ pain?

    <p>A HIDA scan evaluates RUQ pain by assessing gall bladder function and detecting potential obstructions.</p> Signup and view all the answers

    What is the primary action of cholecystokinin on the gall bladder?

    <p>Cholecystokinin primarily stimulates gall bladder contraction to release bile into the small intestine.</p> Signup and view all the answers

    How does somatostatin influence hormone secretion in the presence of high gastric acid levels?

    <p>Somatostatin is released in response to high gastric acid levels, which inhibits the secretion of various hormones.</p> Signup and view all the answers

    What are the effects of GIP on insulin release and gastric acid secretion?

    <p>GIP stimulates insulin release from the pancreas and also blunts gastric H+ secretion.</p> Signup and view all the answers

    Describe the role of vasoactive intestinal peptide (VIP) in the digestive system.

    <p>VIP promotes relaxation of smooth muscle, increases pancreatic bicarbonate secretion, and inhibits gastric H+ secretion.</p> Signup and view all the answers

    What condition is characterized by watery diarrhea and is associated with VIP-secreting tumors?

    <p>VIPoma is the condition characterized by watery diarrhea and is associated with VIP-secreting tumors.</p> Signup and view all the answers

    In patients with carcinoid syndrome, how does octreotide affect symptoms?

    <p>Octreotide significantly improves flushing and diarrhea symptoms in patients with carcinoid syndrome.</p> Signup and view all the answers

    What physiological response occurs when food enters the stomach in relation to somatostatin release?

    <p>Food in the stomach leads to decreased somatostatin release, facilitating hormone release for digestion.</p> Signup and view all the answers

    How are somatostatin and its analog octreotide used in the management of GI bleeding?

    <p>Octreotide reduces splanchnic blood flow and thus is used to manage GI bleeding.</p> Signup and view all the answers

    What distinguishes the hormonal release of GIP compared to other hormones in the digestive system?

    <p>GIP is released in response to glucose, fatty acids, and amino acids, but only after oral intake, not IV glucose.</p> Signup and view all the answers

    Study Notes

    Gastrointestinal Hormones

    • Gastrin is a hormone that increases stomach acid secretion.
    • It is produced by G-cells located in the antrum of the stomach.
    • Gastrin is released into portal vein blood.
    • Its primary action is on parietal cells.
    • Gastrin's effects include:
      • Stimulating H+ secretion by parietal cells.
      • Promoting the growth of gastric mucosa.
      • Being important in gastrin tumors.
      • Increasing gastric motility.
    • Gastrin is released in response to stomach distention, alkalinization, amino acids (especially phenylalanine & tryptophan), vagal stimulation, inhibited by low pH and somatostatin.

    Gastrinoma (Zollinger-Ellison Syndrome)

    • Gastrin-secreting tumors that occur in the duodenum or pancreas.
    • They can also occur in the pancreas in fetuses.
    • A characteristic of this syndrome is excessive acid secretion.
    • The mucosa of the affected areas shows hypertrophy and hyperplasia.
    • Manifestations of the syndrome include:
      • Abdominal pain, relieved by food intake (raises pH).
      • Chronic diarrhea (excessive gastric acid in intestines).Low pH inactivates pancreatic enzymes
      • Excessive gastric acid cannot be neutralized in intestines.
      • Low pH inactivates pancreatic enzymes.
      • Poor digestion, steatorrhea (fat in stool), secretory diarrhea.
      • Gastric ulcers, most commonly located distally in the duodenum or jejunum.
      • Resistance to PPI therapy, causing heartburn.

    Gastrinoma Diagnosis

    • Fasting serum gastrin levels are significantly elevated; greater than 10 times the upper limit of normal.
    • The secretin test differentiates gastrinomas from other causes of elevated gastrin.
    • In a normal individual, secretin inhibits G cells, causing a decrease in gastric pH.
    • Gastrinomas, however, increase gastrin release in response to secretin, making the gastrin levels rise.

    Gastrinoma Treatment

    • High doses of proton pump inhibitors (PPIs) such as omeprazole, lansoprazole, and pantoprazole are used.
    • Octreotide (a somatostatin analog) is another option that inhibits gastrin release.
    • Surgical excision is an option for some patients.

    Pernicious Anemia

    • Autoimmune gastritis causes the loss of parietal cells, which leads to a lack of intrinsic factor.
    • This prevents absorption of Vitamin B12.
    • High gastrin levels are a typical finding in pernicious anemia.
    • G-cell hyperplasia is also present in these cases.

    Cholecystokinin (CCK)

    • Hormone responsible for gallbladder contraction.
    • CCK stimulates the secretion of pancreatic enzymes.
    • Released by I cells mainly in the duodenum and jejunum.
    • Stimulated by fatty acids and monoglycerides (mostly in the small intestine) along with amino acids and small proteins.
    • Actions include gallbladder contraction, stimulation of the vagus nerve and release by the vagus nerve of acetylcholine, relaxation of the sphincter of Oddi, and inhibition of gastric emptying.

    HIDA Scan

    • A method of cholecystography.
    • A diagnostic tool used when ultrasound results are non-diagnostic for RUQ pain.
    • Radioactive tracer (99mTc-hepatic iminodiacetic acid) is administered to image the gallbladder's function.
    • Used to follow the radioactivity and gauge its concentration in the gallbladder and movement through the intestines.
    • Can detect gallbladder obstruction.
    • Cholecystokinin may be given to evaluate gallbladder function.
    • Measuring the gall bladder radioactivity before and after and the ejection fraction are diagnostic tools.

    Secretin

    • Hormone responsible for raising pH in the small intestine.
    • Released by S cells in the duodenum.
    • Released in response to H+ in duodenum & fatty acids in duodenum.
    • Functions include: increase HCO3- secretion by pancreatic duct cells to neutralize gastric acid, allow pancreatic enzymes to function properly, inhibit gastric H+ secretion, suppress gastrin release, increase bile production, promote pancreatic flow, flushing pancreatic enzymes into the intestines.
    • Key clinical use: diagnosing gastrinomas because it stimulates gastrin release from gastrinoma cells.

    Somatostatin

    • Inhibits most GI hormones.
    • Released by D cells throughout the GI tract.
    • Found also in nerves throughout the body.
    • Originally discovered in the hypothalamus.
    • Inhibits growth hormone release.
    • Acts as a hormone and paracrine agent.
    • Stimuli for Somatostatin are low pH and vagus nerve inhibition.
    • Its inhibitory actions include:
      • Gastric H+.
      • Pepsinogen secretion.
      • Gall bladder contraction.
      • Pancreatic fluid secretion.
      • Intestinal fluid secretion.
      • Insulin/Glucagon release.

    Octreotide

    • Analog of somatostatin.
    • Used to treat GI bleeding and other conditions.
    • Reduces splanchnic blood flow (e.g. in bleeding varices).
    • Used in carcinoid syndrome to alleviate symptoms such as flushing and diarrhea.
    • Also inhibits growth hormone secretion, and release of gastrin and glucagon.

    GIP (Glucose-dependent Insulinotropic Peptide)

    • Stimulates insulin release from the pancreas.
    • Also blunts H+ secretion.
    • Released by K cells in the duodenum and jejunum.
    • Stimulates by glucose, fatty acids, amino acids.
    • Only hormone released in response to fats, proteins and carbohydrates.
    • Important note: Oral glucose metabolized faster than IV glucose, causing the IV glucose not to stimulate GIP release.

    VIP (Vasoactive Intestinal Peptide)

    • Synthesized by neurons.
    • Released in response to action potentials onto target cells.
    • Causes relaxation of smooth muscles.
    • Important for the lower esophageal sphincter (LES).
    • Raises pH (similar to secretin).
    • Stimulates pancreatic HCO3- secretion, causing bicarb to draw water and increase fluid secretions.
    • Inhibits gastric H+ secretion.

    VIPoma

    • Rare tumor that secretes VIP in the pancreatic islet cells.
    • Symptoms include watery diarrhea (secretory diarrhea).
    • Diarrhea is tea-colored and odorless, resembling cholera and is associated with hypokalemia(from high volume diarrhea) and achlorhydria (lack of stomach acid).
    • Typical case: Adult (30-50 years). Long-standing watery diarrhea; No response to dietary changes or lactose elimination; High stomach pH; Elevated VIP on serology testing.
    • Treatment initially includes fluid/electrolyte replacement along with Octreotide (somatostatin).
    • Often metastatic when diagnosed and surgical resection may be possible; median survival ~8 years.

    Motilin

    • Released by cells in stomach, intestines, colon.
    • Promotes intestinal motility in the fasting state.
    • Highest levels are found between meals.
    • Significant clinical point: Erythromycin binds motilin receptors and is used to treat gastroparesis.

    Major Hormone Locations

    • Charts showing the locations of gastrin, CCK, secretin, GIP, motilin, VIP, and somatostatin in different parts of the digestive tract (antrum, duodenum, jejunum, ileum).

    Cephalic, Gastric, and Intestinal Phases of Digestion

    • Flowcharts illustrating the stimulation of hormone release at each phase of digestion- cephalic, gastric and intestinal.

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    Gastrointestinal Hormones PDF

    Description

    Test your knowledge on gastrointestinal hormones, focusing on gastrin and its role in gastric function. This quiz also covers gastrinoma, specifically Zollinger-Ellison Syndrome, and its manifestations. Understand the complex relationships between these hormones and digestive health.

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