Melatonin: Therapeutic use, Treatment. Melatonin rehab.

Last modified: Sunday, 31. May 2009 - 5:08 pm

Official names: Melatonin, 5-methoxy-N-acetyltrypt-amine
Street names: Melliquid, mellow tonin, somniset
Drug classifications: Not scheduled

 

Key terms

ENDOCRINE SYSTEM: Organs that produce hormones.
ENDOGENOUS: Produced within the body.
EXOGENOUS: Produced by a source outside of the body.
HORMONE: Substance secreted by a gland into the bloodstream and carried to another part of the body, where it causes a physiological change.
JET LAG: Condition caused by traveling over several time zones in a short period of time.
NORADRENALINE: Chemical produced by the nervous system.
SEASONAL AFFECTIVE DISORDER (SAD): Type of depression that occurs during the fall and winter months.

 

Overview

Melatonin is a natural hormone produced by many animals. In humans, it is produced in several parts of the body, including the pineal gland, which is a small organ located at the base of the brain. Historically, the pineal gland was thought to have some sort of metaphysical function. It was often called the “third eye” and was said to be “the seat of the soul” by Descartes. It is now known to be involved in the neuroendocrine system, which involves the interaction of the nervous and endocrine systems (organs that produce hormones). This interaction results in the regulation of essential body functions. The neuroendocrine system is responsible for the fight or flight response, as well as many other processes that keep people alive and healthy. Melatonin is thought to be important in maintaining certain essential physiological functions such as sleep.
There are many nerve fibers in the pineal gland. Some of these fibers release noradrenalin, a chemical messenger produced by the nervous system. Noradrenalin stimulates certain cells in the pineal gland, called pinealocytes, to produce and release melatonin.
Some parts of the brain, like the cerebral cortex, are much more highly evolved in humans than in other animals. The pineal gland, however, is a very basic organ that first evolved in primitive species. It is found in lampreys, fish, amphibians, and reptiles, as well as in mammals. The hormone melatonin has also been found in insects and plants.
Researchers first hypothesized the existence of melatonin almost 100 years ago. Back in 1917, scientists noticed that an unknown substance from the pineal gland affected melanophores, a kind of pigment cell found in frog skin. More than 40 years later, a dermatologist, Dr. Aaron Lerner, finally isolated this substance from the pineal gland and named it melatonin.
Over the next few decades, researchers learned that melatonin had many other effects in addition to influencing pigmentation in amphibians. Most current research has studied its influence on promoting sleep. Other studies have linked this hormone to other processes such as reducing jet lag, boosting the immune system, and fighting cancer.
Scientists have learned that the retina of the eye and parts of the gastrointestinal tract also produce melatonin. It is not known if the function of melatonin produced by these parts of the body differs from that made by the pineal gland.
The production of melatonin varies over the course of a day. Darkness stimulates the pineal gland to produce melatonin, while the presence of light inhibits the release of this hormone. Melatonin levels are so low during the daytime that they are almost immeasurable. The amount of melatonin starts to increase around 9 p.m. or 10 p.m. Levels continue to increase during the early part of the night and peak at about 2 a.m. to 4 a.m. and thereafter start to decrease through the rest of the morning.
While everyone follows this general pattern of diurnal melatonin secretion, each individual has his or her own unique pattern. Melatonin peaks and valleys can occur at different times in different people and may explain why some individuals are “morning” people, while others are “night owls.”
This circadian rhythm of melatonin production is not limited to humans and animals. Certain types of alga show a daily variability in their synthesis of melatonin. Darkness stimulates melatonin production by these one-celled creatures.
The presence of light influences the pattern of melatonin release. In some people, melatonin is secreted for a shorter period during the shorter nights of summer. But in winter, melatonin release lasts longer during the prolonged darkness in these susceptible individuals. Some scientists hypothesize that this variation in melatonin production may be responsible for seasonal affective disorder (SAD). SAD is a form of depression that occurs during the winter. It is frequently successfully treated by exposure to artificial light.
Artificial light, like natural light, influences the synthesis of melatonin by the pineal gland. Exposure to light during the night will inhibit melatonin production. Research results show that women who work night shifts have an increased risk of getting breast cancer; scientists are investigating whether this alteration in melatonin production may be linked to the development of cancer.
Melatonin secretion also varies over the course of a lifetime. Newborn babies produce very little of this hormone, but after the first few months of life the pineal gland increases its production of melatonin. Very small babies produce a relatively constant amount of melatonin throughout the day and night. They do not have any diurnal variation in the production or release of melatonin. It is not until infants are between nine and 12 weeks old that the pineal gland starts to shift towards a nocturnal production of this hormone. Highest levels occur in children who are about four to seven years old. Older children and adults produce smaller amounts, as production gradually decreases during puberty. The typical adult male produces about 30 micrograms of melatonin during a typical day.
Because melatonin production goes down during puberty, some researchers suspect that the decreasing levels of this hormone are somehow linked to sexual maturation. Melatonin also influences the levels of certain reproductive hormones such as prolactin and luteinizing hormone. Due to these effects, many experts recommend that children, teenagers, pregnant women, and breastfeeding mothers do not take melatonin.
Researchers used to think that older adults produced very little melatonin. Since the elderly tend to have more problems with insomnia and other sleeping disorders, scientists hypothesized that these lower levels of melatonin were the cause of sleeping problems in this population.
However, a study published in the January 2001 issue of the American Journal of Physiology showed that melatonin levels are just as high in older adults as they are in younger individuals. Dr. J. B. Fourtillan measured melatonin levels in 34 healthy adults who were over 65 years of age and in 101 healthy adults who were under 30 years of age. The levels of this hormone did not differ between the two age groups.
Researchers still need to learn a lot about what melatonin does and how it can be safely used. Scientists have not completed enough studies to know exactly what functions melatonin carries out in the human body. Similarly, physicians do not understand at what time during the day or night melatonin should be taken or what dose is most effective. Nor do physicians know enough about the long-term effects of taking melatonin since it has only became popular in the 1990s.
In spite of this lack of information, several popular books came out during the 1990s advocating the supposed usefulness of melatonin as a treatment for everything from insomnia to jet lag to aging. Consumer interest in melatonin increased dramatically. It is estimated that millions of Americans take melatonin supplements as a “natural” remedy.
Although melatonin is a hormone and a drug, it is not regulated by the Food and Drug Administration (FDA). That is because melatonin is naturally found in certain foods. However, the amount of melatonin in over-the-counter medications is a great deal higher than what is found in food, or is produced by the human body. A typical supplement may contain anywhere from 500 micrograms to 5 mg. A supplement containing 500 micrograms will produce blood concentrations similar to those normally found in the human body. Doses of 1-5 mg will result in blood levels anywhere from 10 to 100 times higher than normal.
Melatonin can have different effects depending on when it is taken. If taken slightly before bedtime, it may be useful in adjusting a person’s sleep schedule following a long flight. Taken during the day, however, it will not change the sleeping pattern; it will just make the person sleepy. Similarly, some cancer research suggests that melatonin may be helpful as a cancer therapy if given at the correct time of day. If it is given at the wrong time, it may end up having no effect or may actually increase the risk of developing cancer.
Because melatonin is not regulated by the FDA, commercially available preparations are not subject to the same scrutiny as medications under the direction of this federal agency. Melatonin supplements do not have to be extensively tested in animals and humans before being sold in over-the-counter preparations. Manufacturers do not have to maintain high production standards, nor do they have to be as concerned with instituting FDA-required safety checks. Manufacturers are, however, limited by law in one way: They cannot claim that their product will cure or treat anything. They can only make general statements. While they can say that melatonin helps people sleep, they cannot say that it treats

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