Carcinoid Syndrome Diarrhea and Serotonin

The role of serotonin in Carcinoid Syndrome diarrhea

Serotonin: More than the "happy" hormone

Serotonin is a hormone that is made and released by cells in both the brain and the gut. It's sometimes referred to as the "happy" hormone because serotonin produced in the brain helps regulate mood. But serotonin made in the gut plays an important role in other bodily functions, including bowel movements.

The brain makes 5% to 10% of serotonin in the body.
The serotonin made in the brain stays in the brain, separate from serotonin made in the gut.

The gut makes 90% to 95% of serotonin in the body.
The serotonin made in the gut can travel throughout the body in the bloodstream, but it cannot go to the brain.

Too much of a good thing

In people with Carcinoid Syndrome, serotonin levels can be greater than 5 times the average. An overproduction of serotonin by neuroendocrine tumor (NET) cells can lead to diarrhea, flushing, wheezing, fibrosis, and carcinoid heart disease among other effects.

Let's focus on one of the most common and life-disrupting symptoms of excess serotonin, Carcinoid Syndrome diarrhea. Over time, too much serotonin increases the amount of fluid in the gut. It also speeds up the function of the gut, which causes frequent, or unpredictable diarrhea. Even with somatostatin analog (SSA) treatment, some patients with Carcinoid Syndrome continue to experience diarrhea.

Controlling serotonin may mean fewer "eruptions"

You know how diarrhea can feel a bit...sudden? Kind of like when a volcano erupts? In a volcano, when too much molten rock turns into lava, it rises to the surface and erupts. In your body, excess serotonin can have the same effect. Controlling serotonin levels may be key to avoiding frequent diarrhea.

Speak up about serotonin and Carcinoid Syndrome diarrhea

There are other factors that can lead to Carcinoid Syndrome diarrhea, although higher serotonin levels normally play a role. Talk with your healthcare provider about whether too much serotonin could be the cause of your Carcinoid Syndrome diarrhea.

Could you have better control over serotonin and Carcinoid Syndrome diarrhea?
See how XERMELO can help.

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Important Safety Information and Indication

Important Safety Information and Indication

Important Safety Information

  • XERMELO may cause constipation which can be serious. You should stop taking XERMELO if severe constipation or severe, persistent, or worsening abdominal pain develops. Talk to your doctor if you have these symptoms
  • The most common side effects of XERMELO include nausea, headache, increase in hepatic enzymes, depression, flatulence, decreased appetite, swelling of your hands and feet, and fever
  • Talk to your doctor about all medicines you are taking as some may interact with XERMELO


XERMELO is a prescription pill, used along with somatostatin analog (SSA) therapy, for Carcinoid Syndrome diarrhea in adults who are not adequately controlled by SSA therapy.

For more information about XERMELO, talk to your doctor or see Full Prescribing Information.

You may report an adverse event related to Lexicon products by calling 1-844-LEX-PHAR (1-844-539-7427)  (US only). If you prefer, you may contact the US Food and Drug Administration (FDA) directly. The FDA has established a reporting service known as MedWatch where healthcare professionals and consumers can report serious problems they suspect may be associated with the drugs and medical devices they prescribe, dispense, or use. Visit MedWatch or call 1-800-FDA-1088.