Carcinoid syndrome

Carcinoid syndrome refers to the array of symptoms that occur secondary to carcinoid tumors. Carcinoid tumors are discrete, yellow, well-circumscribed tumors that can occur anywhere along the gastrointestinal tract (GI). They most commonly affect the appendix, ileum, and rectum. These tumors are unique in that they are endocrine in nature. They secrete hormones into the blood stream, which then travel to end organs and act upon them via appropriate receptors. Although quite rare, 15 cases/1,000,000 population, carcinoid tumors account for 75% of GI endocrine tumors. more...

Pathophysiology

Carcinoid tumors secrete vasoactive substances such as serotonin, histamine, catecholamines, and prostaglandins. These hormones acts upon many tissues of the body including the central nervous system, blood vessels of the intestinal tract, and platelets, ultimately altering blood flow. Prior to metastasis, the liver is capable of metabolizing most of the hormones elaborated by such tumors, rendering patients asymptomatic. Only about 5% of patients with carcinoid tumors ever develop symptoms of the carcinoid syndrome which includes, flushing, diarrhea, hypotension, edema, asthma-like bronchoconstriction attacks, and valvular heart disease. The onset of these symptoms suggests that the tumor has metastasized to the liver, allowing serotonin and its various by-products to reach systemic circulation.

Diagnosis

With a certain degree of clinical suspicion, diagnosis is made by measuring the 24 hour urine levels of 5-HIAA (5-hydroxyindoleacetic acid), a breakdown product of serotonin. Patients with carcinoid syndrome usually excrete >25 mg of 5-HIAA per day.

Treatment

For symptomatic relief of carcinoid sydrome:

• Octreotide (somatostatin analogue- neutralizes serotonin and decreases urinary 5-HIAA)
• Methysergide maleate (antiserotonin agent but not used because of serious side effect of retroperitoneal fibrosis)
• Cyproheptadine (antihistamine)

Alternative treatment for qualifying candidates:

• Surgical resection of tumor and chemotherapy (5-FU and doxorubicin)

Prognosis

Prognosis varies from individual to individual. It ranges from a 95% 5 year survival for localized disease to a 20% 5 year survival for those with liver metastases. However, median survival for patients with carcinoid sydrome is 2.5 years from the first episode of flushing.

Synonyms

Thorson-Bioerck syndrome, argentaffinoma syndrome, Cassidy-Scholte sydrome, flush syndrome

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