Carcinoid syndrome

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Carcinoid syndrome

Endocrine system


Carcinoid syndrome


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Carcinoid syndrome

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Carcinoid syndrome p. 356, 592

bronchial carcinoid tumors p. 707

somatostatin for p. 362

treatment p. 725

Cutaneous flushing

carcinoid syndrome p. 357

5-hydroxyindoleacetic acid (5-HIAA)

in carcinoid syndrome p. 357

Heart failure p. 318

carcinoid syndrome p. 592

Octreotide p. 380, 409

carcinoid syndrome p. 359

for carcinoid syndrome p. 725

Pulmonic stenosis

carcinoid syndrome p. 359

Right heart failure

carcinoid syndrome p. 592


in carcinoid syndrome p. 356

Tricuspid regurgitation

carcinoid syndrome as cause p. 359


Carcinoid syndrome refers to a constellation of symptoms like diarrhea, shortness of breath and flushing, which arise when a specific type of tumor called a neuroendocrine tumor begins secreting hormones.

Neuroendocrine tumors were also called “carcinoid tumors” in the past, because of their association with carcinoid syndrome.

Neuroendocrine cells are found in tissues throughout the body, particularly in the epithelial layer of gastrointestinal organs and the lungs. They receive signals from nerve cells and, in response, they release hormones into the blood.

Neuroendocrine cells release a variety of hormones including amines, like serotonin and histamine; polypeptides, like bradykinin, a vasodilator; and prostaglandins which are also powerful vasodilators. The production of these hormones can also be regulated by other hormones.

For example, somatostatin is a hormone that’s made by cells in the hypothalamus as well as the gastrointestinal tract, and it travels through the blood and binds to receptors on the surface of neuroendocrine cells.

Binding of somatostatin inhibits the release of a number of hormones from neuroendocrine cells, including serotonin.

Now, when serotonin does get released from neuroendocrine cells, it enters the liver through the portal vein.

In the liver, some of the serotonin is metabolized to 5-hydroxyindoleacetic acid which is eliminated from the body through the urine.

The remaining serotonin is not metabolized, and this portion remains in the systemic circulation where it has various effects.

In the gastrointestinal tract, serotonin increases motility and peristalsis; in the vasculature, platelets take up the serotonin and later use it to constrict blood vessels, particularly after injury; and in the connective tissue of the heart, it stimulates fibroblasts which make lots of collagen.


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  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
  6. "Carcinoid heart disease: presentation, diagnosis, and management" Heart (2004)

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