Serotonin, Serum

The Serotonin, Serum test contains 1 test with 1 biomarker.

Brief Description: The Serotonin test, also known as a serum serotonin test, measures the concentration of serotonin—a neurotransmitter and hormone—circulating in the blood. Serotonin plays a crucial role in regulating mood, appetite, sleep, and various bodily functions. This test provides valuable insights into serotonin levels and their potential implications on both mental and physical well-being.

Also Known As: 5-Hydroxytryptamine test, 5-HT test, Serotonin Serum Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: Patient should avoid foods high in indoles: Avocado, banana, plum, walnut, pineapple, and eggplant.

Patient should also avoid tobacco, tea, and coffee three days prior to specimen collection.

When is a Serotonin test ordered?

The main indications for ordering this test are symptoms that point to a carcinoid tumor.

Several symptoms and indicators include:

  • Face- and neck-flushing
  • vomiting, nausea, and diarrhea
  • rapid heartbeat
  • coughing, wheezing, and breathing issues

When the findings of the 5-HIAA test are normal or close to normal, this test may be requested initially or as a follow-up test.

What does a Serotonin test check for?

A molecule called serotonin carries signals between nerve cells. Serotonin levels in the blood are determined by this test.

Tryptophan is an amino acid that is converted into the neurotransmitter serotonin. The neurological system, mostly the brain, but also certain cells in the bronchial tubes and gastrointestinal tract, produces it as needed. The platelets contain more than 90% of the serotonin in the blood.

Serotonin participates in the wake-sleep cycle, regulates mood, and helps transfer nerve impulses and constrict blood vessels. The liver converts serotonin into its many metabolites, the majority of which are excreted in the urine as 5-HIAA.

Serotonin often exists in trace levels in the blood. Some carcinoid tumors can produce a lot of serotonin and 5-HIAA, either constantly or sporadically. Carcinoid tumors are slow-growing masses that can develop in the lungs and digestive tract, though they can also affect other organs. They are one of the tumor varieties that develop from neuroendocrine system cells. These cells are present in all of the body's organs and release hormones in response to signals from the neurological system. Particularly when the tumor has progressed to the liver, the serotonin released by carcinoid tumors may cause facial flushing, diarrhea, a rapid heartbeat, and asthma. The term "carcinoid syndrome" refers to this collection of symptoms.

About 8,000 gastrointestinal and 4,000 lung carcinoid tumors are identified annually in the United States, according to the American Cancer Society. There may be many more of these tumors, but the majority are minor and asymptomatic. Carcinoid tumors are referred to as "incidental" tumors when they are found in asymptomatic patients after surgical procedures carried out for other causes. A tiny number of these tumors may eventually enlarge to the point where they impede the bronchial passages of the lungs or the intestines.

Lab tests often ordered with a Serotonin test:

  • Chromogranin A
  • 5-HIAA

Conditions where a Serotonin test is recommended:

The Serotonin test is pivotal in diagnosing and monitoring various conditions, including:

  1. Mood Disorders: Abnormal serotonin levels have been associated with mood disorders such as depression, anxiety, and bipolar disorder.

  2. Gastrointestinal Disorders: Serotonin is also present in the gastrointestinal tract, where it regulates intestinal movement. Altered serotonin levels can contribute to conditions like irritable bowel syndrome (IBS).

  3. Carcinoid Syndrome: Tumors that produce excessive serotonin can lead to carcinoid syndrome, characterized by symptoms like flushing, diarrhea, and heart valve abnormalities.

How does my health care provider use a Serotonin test?

Carcinoid tumors may be identified with a serotonin test. It can be requested either before or after a 24-hour urine 5-HIAA test.

Carcinoid tumors are slow-growing masses that can develop in the lungs and digestive tract, though they can also affect other organs. They are one of a number of tumor forms that develop from neuroendocrine system cells, which can be found in organs all over the body and have both neuronal and endocrine functions.

The serotonin test is not typically used as a monitoring technique to assess the efficacy of treatment or to find a carcinoid tumor that has returned. For this, chromogranin A and 5-HIAA can be employed.

What do my Serotonin test results mean?

Serotonin levels that are significantly higher in a person with carcinoid syndrome symptoms are indicative but not conclusive of a carcinoid tumor. The tumor itself needs to be found, biopsied, and inspected by a pathologist in order to be diagnosed. When a test yields abnormal results, the doctor may typically prescribe an imaging scan to help find any potential tumors.

Serotonin and 5-HIAA levels can be normal and yet a person still have a carcinoid tumor. Serotonin is occasionally or never produced by some carcinoid tumors.

A serotonin-secreting carcinoid tumor is unlikely to exist in a person with no symptoms and normal levels of serotonin and 5-HIAA.

Most Common Questions About the Serotonin test:

Purpose and Indications for the Serotonin Test

Why is the Serotonin test ordered?

The Serotonin test is often ordered to diagnose and monitor the treatment of certain conditions related to serotonin production, including carcinoid tumors and serotonin syndrome. These tumors can produce an excessive amount of serotonin, leading to various symptoms. The test helps confirm a diagnosis and monitor the effectiveness of treatment.

Clinical Significance of Serotonin

What does an elevated Serotonin test result indicate?

Increased levels of serotonin can be indicative of a carcinoid tumor. Carcinoid tumors are slow-growing tumors that predominantly occur in the gastrointestinal tract and lungs. When these tumors metastasize to the liver, they can release large amounts of serotonin into the bloodstream. Elevated levels can also be seen in serotonin syndrome, a potentially life-threatening condition caused by excessive serotonin in the brain. This can result from drug interactions or overdose.

What does a decreased Serotonin test result mean?

Decreased serotonin levels can be associated with conditions such as depression, although the relationship between serotonin levels and mood disorders is complex. Not all individuals with depression have low serotonin, and not all treatments for depression aim to increase serotonin levels.

Interpretation and Follow-up

How are the results of the Serotonin test interpreted?

Interpretation of the Serotonin test depends on the reference range of the laboratory performing the test. Generally, levels outside the standard range suggest a need for further investigation. Elevated levels, particularly when combined with clinical symptoms, may point to conditions like carcinoid tumors.

If my Serotonin levels are abnormal, what subsequent tests or treatments might be recommended?

If serotonin levels are found to be elevated, additional tests may be ordered to confirm the presence of a carcinoid tumor or other related conditions. Imaging tests, like CT or MRI scans, can help locate potential tumors. For low serotonin levels, especially when linked to mood disorders, treatments may include antidepressant medications or therapies.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: 5-HT, Serum, 5-Hydroxy Tryptamine, Serum, Serotonin Serum

Serotonin, Serum

*Process times are an estimate and are not guaranteed. The lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

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