Carcinoid Syndrome

Carcinoid syndrome is the term given to explain the various symptoms presented by patients with carcinoid tumors. Carcinoid tumors are the slow-growing tumors of the neuroendocrine system that belongs to the amine precursor uptake and decarboxylation (APUD) system.

These tumors are thought to arise from enterochromaffin cells, also known as kulchitsky cells. These tumors comprise a broad family of tumors, most commonly arising in the lungs and bronchi, small intestine, appendix, rectum, and thymus and pancreatic neuroendocrine tumors. Other less common neuroendocrine tumors include those arising in the parathyroid, thyroid, adrenal, and pituitary glands.

Carcinoid syndrome is mainly because of the release of certain hormones and chemicals that are produced by the tumor. The symptoms vary from person to person depending on the size, location, and degree of hormone secretion by the tumor. Tumors that are located in the small intestine or appendix are more likely to cause carcinoid syndrome than tumors in other locations. The most common symptoms include flushing, nausea, difficulty in breathing, chest pain, pain abdomen, cramps, diarrhea, palpitations, and fluctuation in the heart rate

The diagnosis of carcinoid syndrome is done on the history, physical examination, and investigations like blood and urine levels of various hormones, imaging tests to look for the tumor and its extent of spread are advised. A biopsy is needed to confirm the diagnosis. Surgery is the mainstay of the treatment. Other treatments which help to reduce the symptoms of carcinoid syndrome include octreotide, telotristat ethyl, and Interferon-alpha.

Carcinoid Syndrome: Causes

The development of carcinoid syndrome depends on the location of the tumor, the size of the tumor, and the degree of hormone secretion by the tumor. In general, tumors that are located in the small intestine or appendix are more likely to cause carcinoid syndrome than tumors in other locations.

• Carcinoid syndrome is mainly due to the secretion of certain hormones and chemicals by carcinoid tumors. Carcinoid tumors are neuroendocrine tumors that develop from hormone-producing cells in the body. These tumors can be found in various parts of the body, such as the lungs, stomach, pancreas, and intestines.

• Various hormones and chemicals such as serotonin, histamine, bradykinin, prostaglandins, and tachykinins are produced by carcinoid tumors. The symptoms are mainly because of the effect of these hormones and chemicals.

• Various hormones and chemicals released by these tumors act on certain receptors in the body, such as the serotonin receptor and the histamine receptor which results in various symptoms.

Carcinoid Syndrome: Symptoms

The patient with carcinoid tumors presents with the following −

• Patients with carcinoid syndrome mainly present with flushing where there is sudden reddening and warming of the face and neck. Flushing can also be associated with sweating, increased heartbeat, and difficulty in breathing.

• Diarrhea, usually associated with pain in the abdomen, cramps, and nausea if the carcinoid tumor is located in the gastrointestinal system.

• Abdominal pain, which may be intermittent or constant.

• Wheezing, difficulty in breathing, and chest pain if the tumor is located in the lungs.

• Some patients present with palpitations and decreased blood pressure.

• Weight loss is often due to a loss of appetite or changes in metabolism.

• Fatigue or weakness can be caused by the tumor or by the hormones it produces.

• Fluctuation in the blood pressure

Carcinoid Syndrome: Risk Factors

Several factors play an important role in the development of carcinoid syndrome as well as carcinoid tumor which include −

• Carcinoid tumors that are located in the small intestine, appendix, or rectum are more likely to cause carcinoid syndrome than tumors in other locations

• Larger size tumors have more symptoms than smaller tumors due to the secretion of larger amounts of hormones and chemicals by larger tumors

• Tumors that secrete larger amounts of hormones and chemicals are more likely to cause symptoms than tumors that secrete smaller amounts.

• More common in people over the age of 50yrs

• Women are more susceptible than men.

• Family history of carcinoid tumors as it is known to occur because of the genetic mutation

• People with genetic diseases such as multiple endocrine neoplasia type 1 (MEN1), neurofibromatosis type 1 (NF1), and Von Hippel-Lindau disease (VHL) are also at an increased risk

• Exposure to certain chemicals such as radon, asbestos, and pesticides, may increase the risk

• People with inflammatory bowel disease (IBD), such as Crohn's disease or ulcerative colitis

• Smoking for a longer duration

Carcinoid Syndrome: Diagnosis

Diagnosis of the carcinoid tumor is done by the following −

• A history of various symptoms and similar conditions in the family and a physical examination of the patient are carried out to look for any signs of a tumor and to assess the presence and severity of symptoms associated with carcinoid syndrome.

• Blood and urine tests − measuring the levels of certain chemicals and hormones produced by the tumor, such as serotonin, chromogranin A, and 5-HIAA (5-hydroxy indole acetic acid) can be used to help diagnose carcinoid syndrome. Increased levels of these substances can indicate the presence of a carcinoid tumor.

• Imaging studies − Imaging studies, such as CT scans, MRIs, and PET scans, help to identify the location and size of the tumor and to see for the spread of the tumor to other parts of the body. Associated complications of the tumor, such as liver metastases or bowel obstruction can also be evaluated through the imaging tests

• Biopsy − A biopsy is needed to confirm the diagnosis of a carcinoid tumor. A small sample of the tissue is taken and examined under the microscope.

• Functional imaging studies − Functional imaging studies, such as octreotide scans or gallium-68 dotatate scans, also help to identify the presence of tumors and the extent of neuroendocrine tumors and metastases by detecting the expression of somatostatin receptors on the surface of the cells.

Carcinoid Syndrome: Treatment

Treatment of the carcinoid syndrome includes treating the carcinoid tumor. The treatment options include.

• The mainstay of the treatment involves surgical removal of the tumor and any affected tissue or organs. Surgical treatment is more effective in cases of small, localized tumors.

• Symptomatic treatment should be done to relieve the symptoms. Painkillers can be given to ease the pain.

• Octreotide is a synthetic version of somatostatin, a hormone that inhibits the release of hormones and other substances from the tumor. Hence, it helps to reduce flushing, diarrhea, and other symptoms.

• Telotristat ethyl reduces the production of serotonin, a hormone that is released by carcinoid tumors hence reducing the symptoms

• Interferon-alpha slows the growth of carcinoid tumors and improves symptoms.

Carcinoid Syndrome: Prevention

There are no specific measures to prevent the treatment of carcinoid syndrome. some of the steps taken can help to reduce the symptoms which include −

• Regular screening in individuals having a family history of carcinoid tumor.

• Lifestyle changes such as eating a healthy balanced diet, regular exercise, and avoiding alcohol, stress, and high-fat or low-fiber content food, can help prevent the symptoms of carcinoid syndrome.

• Regular follow-up is important if the patient has been diagnosed with having a carcinoid tumor to avoid further progression of the tumor and to treat it adequately.

Conclusion

Carcinoid syndrome is the set of various symptoms presented by a patient suffering from a carcinoid tumor. Carcinoid tumors are neuroendocrine tumors that originate from hormone-producing cells. Certain chemicals and hormones produced by these tumors are responsible for carcinoid syndrome.

The main symptoms include flushing, pain abdomen with cramps, diarrhea, palpitations, and fluctuation in the heart rate. Various factors are responsible for the occurrence of carcinoid syndrome.

The diagnosis is based on the history, clinical examination, and imaging tests. A biopsy confirms the diagnosis. Treatment involves the removal of the tumor and pharmacological therapy.