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Hormonal and Rare Conditions Carcinoid Syndrome What causes carcinoid syndrome?
What causes carcinoid syndrome?
About carcinoid syndrome

What causes carcinoid syndrome?

Carcinoid syndrome is a set of symptoms that can sometimes develop if:1

An infographic describing how carcinoid syndrome can develop. Carcinoid syndrome can develop if you have a GEP-NET that has spread (metastasised) to the liver and it is producing too much of a certain hormone.

Serotonin is a hormone that is critical for your body. Among other things, it can influence your mood, memory, body temperature, and sleep.2 However, if a tumour is releasing excess serotonin, as in carcinoid syndrome, it can cause negative side effects and lead to further complications such as carcinoid crisis and carcinoid heart disease.1 More information on carcinoid crisis and carcinoid heart disease can be found on our complications of carcinoid syndrome page.

It's not clear what causes GEP-NETs, but it is thought to be influenced by:3

Some substances in food, high energy radiation, certain chemicals, genetics (i.e. you get it from your parents), tobacco smoke, and ultraviolet radiation from the sun.

References

  1. CRUK. Carcinoid syndrome. Available at: https://www.cancerresearchuk.org/about-cancer/neuroendocrine-tumours-nets/about-carcinoid-syndrome. Last accessed April 2025.
  2. Cleveland Clinic. Serotonin. Available at: https://my.clevelandclinic.org/health/articles/22572-serotonin. Last accessed April 2025.
  3. CRUK. Genes, DNA and Cancer. Available at: https://www.cancerresearchuk.org/about-cancer/what-is-cancer/genes-dna-and-cancer. Last accessed April 2025.