Serotonin (5-HT) • What do high / low values ​​mean?

Also known as the happiness hormone: Serotonin is a neurotransmitter in the nervous system. In laboratory tests, it is called 5-hydroxy-tryptamine (5-HT). A metabolic product, 5-hydroxyindolylacetic acid (5-HIES), is measured in the blood in a laboratory test.

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Blood count: important values ​​and what they mean

What is serotonin?

The messenger substance serotonin transmits information from nerve cell to nerve cell in the human body. It is therefore found in the entire nervous system, and serotonin also has an effect on thrombocytes (blood platelets) and in cells of the intestine. In the brain, serotonin influences the following processes:

• Body temperature
• hunger
• Feelings
• Reward system
• Mood and drive
• State of consciousness and sleep-wake rhythm
• Pain assessment

In addition, serotonin is involved in other processes in the body:

• Widening and narrowing of the blood vessels
• Dilatation and constriction of the bronchi
• Blood clotting: Serotonin stimulates blood platelets
• Bowel movements

When is the serotonin level determined?

Contrary to the common assumption that the serotonin value could say something about depression, for example, this is not the case. The measurement of 5-HIES in the blood does not allow any conclusions to be drawn about the amount of serotonin in the brain. This would require an examination of the spinal cord fluid, a so-called liquor puncture.

Serotonin (5-HIES) is determined in the blood when a carcinoid is suspected. A carcinoid is a neuroendocrine tumor that usually forms in the gastrointestinal tract and produces excessive serotonin. Typical symptoms are diarrhea and flushed face.

Serotonin normal values ​​(5-HIES)

The normal values ​​of the breakdown product 5-HIES of serotonin are determined either via a blood sample or a 24-hour urine collection.

The reference ranges for normal values ​​of serotonin are:

• in the blood: 50–200 µg / l or 250–800 µg / 10^12th Platelets
• in the urine: <200 µg / d

The standard values ​​can vary depending on the method used and the laboratory.

Food and drugs affect serotonin

Since various foods, luxury foods and also drugs influence the serotonin level, it should be avoided two to three days before the blood sample is taken:

Exemplary drugs that can cause falsely high serotonin levels:

• Paracetamol
• Coumarins
• Mephenesin
• phenobarbital
• Ephedrine
• Amphetamines

Exemplary Drugs That May Cause Falsely Low Serotonin Levels:

What does a serotonin level that is too low mean?

Even if it seems reasonable to assume that a serotonin level that is too low could indicate depression or anxiety disorders, this is not the case. Clinically, i.e. from the disease point of view, a level that is too low is not important.

Meaning of increased serotonin levels

If the serotonin level is significantly increased, this is an indication of a carcinoid. Elevated values ​​can also occur in epilepsy and celiac disease. If a carcinoid is suspected, further investigations will follow.