Serotonin and melatonin are chemically related monoamine neurotransmitters responsible for regulating mood and health. Serotonin can contribute to feelings of well-being, whereas melatonin can help to regulate the circadian rhythms of several biological functions. Deficiencies in serotonin and melatonin can cause a host of health complications, for which treatments are available. Before trying any of these treatments, consult your doctor.
Biosynthesis
Both serotonin and melatonin are derived from the amino acid tryptophan, states the National Institutes of Health. Tryptophan is converted to serotonin by the enzymes tryptophan hydroxylase, of which there are two forms, and aromatic L-amino acid decarboxylase.
The majority of serotonin synthesized in the body is located in the gut, with the remaining serotonin produced in serotonergic neurons in the central nervous system.
The pineal gland of the brain produces melatonin. The synthesis of melatonin begins with the uptake of tryptophan, where it is again converted enzymatically to produce serotonin. These serotonin molecules are then processed by the enzymes serotonin N-acetyltransferase and hydroxyindole-O-methyltransferase to produce melatonin, the NIH reports.
Functions
Most of the serotonin produced in the body regulates intestinal movements. However, it is the role serotonin plays in controlling brain activity that garners the most attention. Serotonin can also help to regulate mood, appetite and sleep, as well as being particularly associated with an individual's perception of resource availability.
Melatonin can help to control the body's circadian rhythms, also known as the sleep-wake cycle, states the NIH. Predominantly produced at night, melatonin can cause drowsiness and a fall in body temperature.
Deficiencies
Serotonin deficiency is linked to mental illness, particularly depression, according to MedlinePlus. Symptoms of depression specifically linked to a dysfunction in serotonergic neurotransmission include loss of appetite, decreased libido, suicidal thoughts, aggressive behavior, and irritability.
Symptoms of melatonin deficiency include insomnia or frequent waking. As melatonin levels decrease with age, so these behaviors often occur in the elderly. Melatonin deficiency can also affect the production of sex hormones.
Treatment
Serotonin is targeted in the treatment of depression, but is not prescribed in its native form. Instead, many medications for depression are aimed at stopping the breakdown of serotonin, such the monoamine oxidase inhibitors, MAOIs, or increasing the extracellular level of serotonin, such as the selective serotonin reuptake inhibitors, SSRIs, the Upsala Journal of Medical Sciences, notes. The SSRIs, which includes the brands Prozac, Celexa and Zoloft, are more widely prescribed than the MAIOs, as the SSRIs cause fewer side-effects.
Melatonin is often used to treat sleep disorders, such as insomnia and delayed sleep phase syndrome, says MedlinePlus. It is also used to treat sleep problems in children with developmental disorders, including autism and cerebral palsy.
Supplements
Many supplements claim to boost serotonin and melatonin levels. Serotonin cannot pass the blood-brain barrier, so serotonin itself does not enhance mood and may interfere with bowel movements. Supplements that may boost serotonin levels include tryptophan and 5-HTP, the molecules used by the body to synthesize serotonin.
The pineal gland of the brain sits outside the blood-brain barrier, meaning that melatonin can be used in its native form. According to the NIH, it alleviate the symptoms of jet lag and insomnia.
References
- MedlinePlus: Melatonin
- "Reviews in Endocrine and Metabolic Disorders"; Melatonin formation in mammals: in vivo perspectives; A Chattoraj et al; 2009
- "Upsala Journal of Medical Sciences"; Serotonin, genetic variability, behaviour, and psychiatric disorders -- a review; N Nordquist and L Oreland; 2010
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