In spirit of studying for the ZRT Cup Competition , I was looking through some old Pathology notes and came about an interesting condition that has slipped my mind, up until now: Carcinoid Syndrome.

What is Carcinoid Syndrome?
Carcinoid syndrome occurs from carcinoid tumors (created by neuroendocrine cells) within the body, which secrete amine/peptides/catecholamines, particularly serotonin, bradykinin, kallikrein, and even histamine in some instances. These tumors can originate in specific sites within the body including: liver, ovaries, intestine, or appendix. The most common site of origin for these neuroendocrine tumors, which secrete vasoactive substances, to form is within the gastrointestinal tract, spreading to the liver via the portal circulation.

However, the only indication of the symptoms of “carcinoid syndrome” will occur when metastasis of these tumors arrive at the liver, which is involved in hormone breakdown and catecholamine production and catabolism. Then, from the liver, because of the inferior vena cava’s direct connection to the right side of the heart, increased levels of catecholamines can produce vegetations on the heart valves, resulting in cardiovascular pathology as well. Now if your interest is not peaked yet, hold onto your chair (haha okay maybe its not THAT exciting…).

The most interesting part of this syndrome is the decreased incidences of tumors within the lungs. Why? I bet you are wondering. Well the lung epithelium contains an enzyme (monoamine oxidase, MAO) which breaks down serotonin, bradykinin, and kallikrein, leading to inactivation of these peptides, therefore no pathology associated with their deposition. [However, if there is an overload of serotonin within the body activating the MAO enzyme, it may reach a critical threshold that causes it to not work as effectively. So it is possible that there may be lung tumors, although not as likely] See, I told you it was interesting

Amino acids play a major role in regulating production and development of most neurotransmitters within the body. L-Tryptophan is an important amino acid in the production of serotonin within the brain and the body. Serotonin is normally involved with a lot of body functions, including those involved with the central nervous system and mood, cardiovascular system, and gastrointestinal system. We mostly know serotonin and its effect on mood, particularly for individuals who are suffering from depression. But serotonin is also involved specifically in appetite, sleep, memory, learning, mood, temperature regulation, muscle contraction, and hormonal/endocrine regulation.

So what’s so bad about having too much serotonin? It seems like it has pretty positive effects on the body. Right? Wrong. Like I’ve mentioned in previous posts, too much of anything is never a good thing. Everything in moderation. Too much serotonin, and other catecholamines within the body can result in toxicity and produce the characteristic symptoms of carcinoid syndrome below > Flushing of the face
> Right sided heart valve lesions (tricuspid and pulmonic valves)
> Bronchoconstriction (difficulty breathing)
> Metastases to the liver or ileum (gastrointestinal tract)
> Diarrhea
> Abdominal pain
> Blood in the stool
> Nausea and vomiting
> Weight loss

Other conditions that you might want to keep in mind…
> Idiopathic flushing
> Ingestion of certain foods and medications
> Adverse drug reactions
> Thyroid cancer
> Menopause
> Serotonin syndrome

Now, I want to take a moment to mention Serotonin Syndrome, mostly because it involves the same neurotransmitter: Serotonin. And it also involves an excess of it. But comparing carcinoid syndrome and serotonin syndrome is like comparing an apple to a banana, they are just not the same. Carcinoid syndrome develops from abnormal neuroendocrine cells within the gastrointestinal tract, while serotonin syndrome is an adverse drug reaction to many anti-depressants, psychedelics, herbs (St. John’s Wort, for example), serotonin inhibitors, or ecstasy (MDMA), for example. Also, the clinical picture of serotonin syndrome is quite different than carcinoid syndrome > Hyperreflexia
> Restlessness
> Tremor
> Diaphoresis
> Confusion
> Muscular rigidity

Carcinoid syndrome is a condition of immediate hospitalization, due to necessity to remove the neuroendocrine secreting tumors, wherever they may be located within the body. Serotonin syndrome is also an immediate Emergency Room referral. Please consult a licensed medical professional if you have any questions concerning this disorder. This post is intended for informational purposes only.

References:
- Pathology, Bastyr University. Fall -Spring 2011.
- http://web.ebscohost.com/dynamed/detail?vid=3&hid=110&sid=3ef1d7c4-eb48-40f8-a78b-5f6520fd1348%40sessionmgr112&bdata=JnNpdGU9ZHluYW1lZC1saXZlJnNjb3BlPXNpdGU%3d#db=dme&AN=114031
- http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001387/
- http://emedicine.medscape.com/article/282515-overview
- http://www.mdconsult.com/das/pdxmd/body/330834928-3/1299894277?type=med&eid=9-u1.0-_1_mt_1014648
- http://serendip.brynmawr.edu/bb/neuro/neuro99/web1/Byrd.html
- http://www.carcinoid.org/
- http://www.jfponline.com/pages.asp?aid=636