What breaks down serotonin?
The messenger substance serotonin, colloquially known as the happiness hormone, fulfills various functions in the body. To ensure that they run smoothly, the body itself produces serotonin. The basis for this is the amino acid L-tryptophan, which is first converted to the amino acid 5-hydroxytryptophan (5-HTP) and then to serotonin with the help of certain enzymes. Conversely, the body can also break down serotonin again - in various ways.
Serotonin breakdown in the body
The actual breakdown of serotonin in the body occurs through enzymes called monoamine oxidase (MAO for short). They convert serotonin into urea via a chemical process in which an amino group is cleaved off. This produces hydroxyindoleacetic acid, which is excreted by the kidneys. Its content can be detected in the urine using an appropriate test.
Some drugs make use of this natural degradation process or inhibit it. MAO inhibitors prevent the body from breaking down serotonin and thus ensure that the neurotransmitter remains in the body longer. As a result, it can maintain its effect for a correspondingly longer time. MAO inhibitors are traditionally used as antidepressants, but also to treat anxiety disorders or obsessive-compulsive disorders.
Two processes that lower serotonin
There are two other processes that lower the amount of serotonin that is bioavailable in the body: First, a large amount of serotonin is stored in platelets and in the intestinal mucosa after it is released. Even though serotonin cannot break down in this way, it is deprived of certain functions here and is therefore no longer freely available.
On the other hand, serotonin is converted into the hormone melatonin in the pineal gland via special chemical processes and with the cooperation of certain enzymes. Melatonin is, so to speak, the antagonist of serotonin, because while the latter primarily serves to support the waking state, melatonin controls and promotes sleep. This is why serotonin is often referred to as the waking hormone and melatonin as the sleep hormone.
However, to produce melatonin, the body needs not only serotonin but also darkness. This is because the enzymes responsible for the conversion are inhibited by light. This is why the body produces considerably more melatonin in winter, when it is dark earlier and longer, than in summer. As a result, we often feel more tired and sluggish in winter than in spring or summer.
Conclusion on serotonin depletion
The body can lower or break down serotonin itself, once directly with the help of enzymes (MAO) via certain chemical processes. So-called MAO inhibitors can delay the breakdown of serotonin and thus keep the serotonin level in the body at a higher level for a longer period of time. In addition, the body can also lower serotonin indirectly by converting it to melatonin in the pineal gland. This process is enhanced by darkness. Although storage in platelets and the intestines does not lead to a reduction in the messenger substance, the storage process can lower the amount of bioavailable serotonin so that it is no longer freely available to the organism.