Serotonin is both a hormone and neurotransmitter. It is essential for regulating mood, movement, sleep & much more. What else does it do, and what happens when it\u2019s out of balance? Read on to find out more!<\/p>\n
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Serotonin is an important signaling molecule throughout the brain and body. It is commonly known as the “happiness neurotransmitter” or the “happiness hormone” due to its prominent role in regulating mood<\/a>.<\/p>\n Serotonin plays an important rol,e in the brain, where its main job is to transmit messages between nerve cells. According to some scientific theories, serotonin is involved in all aspects of human behavior [R<\/a>, R<\/a>].<\/p>\n However, brain serotonin makes up less than 2% of the total serotonin found in our bodies. Most serotonin (over 90%) is actually made, stored, and released by the gut. In addition, about 5-8% of serotonin is stored in platelets circulating in the blood [R<\/a>, R<\/a>, R<\/a>].<\/p>\n As such, the roles of serotonin in the body are many and diverse. Research suggests that serotonin influences [R<\/a>, R<\/a>, R<\/a>, R<\/a>, R<\/a>]:<\/p>\n Originally discovered in the 1940s, serotonin \u2014 also known as 5-hydroxytryptamine<\/i>, or \u201c5-HT\u201d for short \u2014 is currently believed to play many pivotal roles in mood, behavior, gut, and overall optimal body function (homeostasis<\/i>). So-called \u201cimbalances\u201d or other abnormalities in serotonin function have been linked with symptoms that may interfere with mental and physical health, and which can significantly impair quality of life [R<\/a>, R<\/a>, R<\/a>].<\/p>\n According to some hypotheses and limited research, increasing serotonin levels may help with anxiety, depression, migraines, and constipation-predominant irritable bowel syndrome. However, more large-scale studies are needed [R<\/a>, R<\/a>, R<\/a>].<\/p>\n The majority of serotonin is made, stored, and released by cells in the gut lining (enterochromaffin cells<\/i>). These cells make serotonin from the amino acid L-tryptophan<\/i><\/a>, which is the main \u201cbuilding block\u201d, or metabolic precursor<\/i> of serotonin [R<\/a>, R<\/a>].<\/p>\n Certain specific types of bacteria<\/a> in the human digestive tract are believed to boost serotonin production in the gut. Gut flora<\/a> actually balances tryptophan metabolism (via the kynurenine pathway<\/i>), influencing the amount of L-tryptophan available for making serotonin [R<\/a>, R<\/a>].<\/p>\n However, serotonin produced by the gut cannot cross the blood-brain barrier<\/a>. That is why brain cells must produce their own serotonin, either from L-tryptophan<\/i> or 5-hydroxytryptophan<\/i> (5-HTP<\/a>), a byproduct of L-tryptophan [R<\/a>, R<\/a>].<\/p>\n Conversely, excess serotonin and the brain and gut is \u201cdeactivated\u201d by several different mechanisms. For example, proteins called serotonin transporters<\/i> effectively \u201cclean up\u201d or \u201cremove\u201d (re-uptake<\/i>) serotonin from neural synapses, and bring them back into neurons where it can be reused [R<\/a>, R<\/a>].<\/p>\n Alternatively, serotonin that is released into the bloodstream either gets taken up (absorbed) by platelets<\/a>, or is broken down (metabolized<\/i>) in the liver and lungs by enzymes called monoamine oxidase<\/i> (MAO-A<\/a>), aldehyde<\/i>, and alcohol dehydrogenase<\/i> [R<\/a>].<\/p>\n Serotonin is just one member of the \u201cmonoamine<\/i>\u201d family of neurotransmitters, which also includes other major neurotransmitters such as norepinephrine<\/a> and dopamine<\/a>. Researchers currently believe that all of these neurotransmitters work together to influence and regulate mood<\/a> [R<\/a>].<\/p>\n By extension, a person\u2019s levels of each of these neurotransmitters may affect their mood. For example, a meta-analysis of data from more than 50 different studies reported that artificially depleting the levels of these neurotransmitters can cause \u201clow mood\u201d and other related symptoms (this is typically done by depleting the body of the metabolic precursors<\/i> needed to make these neurotransmitters, such as tryptophan<\/i><\/a> or tyrosine<\/i><\/a>). However, these effects were only observed in individuals who had certain pre-existing risk factors \u2014 such a prior diagnosis of depression, or a family history of depression disorders \u2014 and are not necessarily seen in otherwise healthy people [R<\/a>].<\/p>\n Imbalances in the levels or relative activity of serotonin, dopamine, and norepinephrine have also been proposed to play a role in other common psychiatric conditions, such as bipolar disorder [R<\/a>].<\/p>\n However, some researchers have proposed that combined low levels of these three neurotransmitters \u2014 and not just low serotonin alone \u2014 may be important for understanding how these mood disorders originally develop and progress [R<\/a>].<\/p>\n In the pineal gland, serotonin is used to make melatonin<\/a>, a hormone that synchronizes the body\u2019s \u201cbiological clock\u201d or circadian rhythm<\/a>. When serotonin is low, that limits the amount of melatonin that can be made in the body, potentially interfering with the sleep-wake cycle [R<\/a>].<\/p>\n\n
What Does Serotonin Do?<\/strong><\/span><\/h2>\n
Production and Removal<\/strong><\/span><\/h3>\n
Other Neurotransmitters<\/strong><\/span><\/h3>\n
Monoamines<\/h4>\n
Hormones<\/h4>\n