Carcinoid Tumors B&B

Question 1

what type of cells make up carcinoid tumors?

Answer 1

neuroendocrine cells - can develop in GI tact (small intestine most common), lungs, pancreas

secrete serotonin

Question 2

what symptoms are caused by carcinoid tumors (2) and why?

Answer 2

diarrhea + flushing due to serotonin secretion

serotonin stimulates GI motility and fibroblast growth (may cause cardiac valve pathology)

note - carcinoid syndrome will only occur if there is metastasis to liver, because the liver/lungs metabolize serotonin

Question 3

development of carcinoid syndrome is contingent on metastasis to where? Why?

Answer 3

carcinoid tumors (in GI) secrete serotonin (—> flushing/diarrhea), but carcinoid syndrome will not occur unless there is metastasis to liver

this is because serotonin is metabolized/inactivated by liver and lungs

this also means there is generally no left-sided heart syndromes, because serotonin is inactivated in the lungs

Question 4

patients with carcinoid syndrome have altered metabolism of _______, which can lead to _____ deficiency

Answer 4

carcinoid tumors secrete serotonin

patients have altered tryptophan metabolism - normally only 1% is used to form serotonin, but up to 70% in carcinoid syndrome

tryptophan also used to form niacin (B3), so carcinoid syndrome —> pellagra

Question 5

Pt presents w/ weight loss, flushing, and diarrhea. Labs show elevated 5-HIAA. Given their symptoms, where should you look for metastasis? Which vitamin may require supplementation?

Answer 5

dx = Carcinoid syndrome: serotonin-secreting tumor, only cause symptoms if there is metastasis to liver because lungs/liver metabolize/inactivate serotonin

causes altered tryptophan metabolism (up to 70% shuttled towards forming serotonin) —> may develop niacin (B3) deficiency (Pellagra) because tryptophan is depleted (and also needed for B3 formation)

Question 6

levels of which metabolite can be used to diagnosis carcinoid syndrome?

Answer 6

carcinoid syndrome is due to serotonin-secreting tumor (usually small intestine)

5-HIAA (5-hydroxyindoleacetic acid) is metabolite of serotonin (via monoamine oxidase/MAO) that appears in urine - dx made via 24h urine sample

Question 7

fill in the blank:
serotonin (5-HT) is metabolized via _______ to 5-hydroxyindole acetaldehyde, which is then metabolized into ______, which can be detected in the urine

Answer 7

serotonin (5-HT) is metabolized via monoamine oxidase (MAO) to 5-hydroxyindole acetaldehyde, which is then metabolized into 5-hydroxyindoleacetic acid (5-HIAA), which can be detected in the urine

Question 8

how does carcinoid syndrome affect the heart?

Answer 8

[serotonin-secreting tumor]

serotonin stimulates fibroblast growth —> fibrous deposits on tricuspid/pulmonic valves may cause stenosis or regurgitation

left-sided lesions are rare because serotonin is inactivated in the lungs and liver)

Question 9

what is the pharmacological treatment for carcinoid syndrome?

Answer 9

octreotide: somatostatin agonist —> inhibits release of bioactive amines (serotonin, catecholamines, histamine)

helps improve flushing and diarrhea