I started my interest in Melatonin (a polypeptide hormone produced by the Pineal Gland) when I was an intern at Ancona University (Italy). At that time I was interested in chronobiology and interactions between environment and neuroendocrine – reproductive system.
The Pineal Gland (also called Epiphysis) is a small endocrine gland located behind the third ventricle and below the Corpus Callosum, practically in the brain center. It’s connected to the surrounding brain structures but mainly receives nerve fibers from the suprachiasmatic nucleus of the Hypothalamus through the Autonomomic Nervous System.
The suprachiasmatic nucleus of the Hypothalamus is considered one of the main centers of biological internal clock regulation and it is directly connected to the retina nerve fiber and therefore to information on ambient light variations. The Epiphysis is therefore a typical neuroendocrinal structure (such as the Adrenal Gland) where the nerve signal (alternating of light / dark) is translated into a message influencing Melatonin secretion in a circadian manner.
Its particular anatomical location still fuel many suggestions about its role. For example, in the sixteenth century Descartes placed here the seat of the soul. In 1899 it is started to assume a functional connection with the endocrine hypothalamus-pituitary-ovary axis and this was done thanks to Ogle and Heuber.
Melatonin secretion is strongly affected and it is strictly dependent of day-night (light-dark) rithm, taking in the
blood a typical circadian cycle with higher levels during the night and lower during the day. Telling the truth, there also are a hormone seasonal variations and in women was demonstrate a variation in the night peak related to menstrual cycle (with lower levels in the peri-ovulatory period) and additional regulatory signals originate from other hormones (such as those ovarian and adrenal hormones).
Bloud Melatonin levels tend to decrease progressively with age.
Here are main actions attributed to Melatonin, outside legends or myths artificially constructed.
– The action is substantially antigonadotropic. The Pineal Gland has an important inibitory role on sexual development until puberty. Pineal Gland tumors were associated with precocious puberty. In some small animals it regulates seasonal reproductive rhythms and can not be excluded that in women could cooperate with regulating menstrual and ovulation systems.
Secretory abnormalities have been described in hypothalamic and stress amenorrhea. It is not excluded that many ovulatory disorders may be related to an alteration of its circadian rhythm.
Very interesting the recent use of Dietary Supplements containing Melatonin, Myo-Inositol and Folic Acid in premature ovarian failure (POF) and ovulation induction: in fact, this compounds showed to improve ovarian response in cycles of ovulation induction and in some forms of ovarian insufficiency.
INSOMNIA, ENVIRONMENTAL ADAPTIVE DISORDERS:
– While Melatonin is not the main regulator of sleep is undeniable nonetheless its ability to induce sleep (reduction of the latency time before falling asleep); also seems to improve the quality of sleep itself and has been used with success in the treatment of Insomnia;
– It plays an important role in the environmental adaptive disorder like in journeys which involve significant changes in timezone. Administration of melatonin is the best pharmacological remedy to combat symptoms classified under the “jet lag disorder “;
– It is effective in combating disorders such as fatigue and a feeling of malaise resulting from disruption of normal sleep cycle – wakefulness (light – dark) – resulting for example in repeated rounds of night work; many give to secretion of melatonin a function of pacemakers (system controller) and other metabolic and hormonal functions.
– It is involved in almost all branches of medical science, ranging from Aging (anti-oxidant effects) to Oncology, from Cardiovascular diseases to immunology, but regard these fields of medicine are needed more and more scientific evidence.
– Night exposure to light;
– Use of certain antihypertensive adrugs, anti-inflammatory drugs, tranquilizers (Benzodiazepines);
– Dietary deficiency of Tryptophan (an essential amino acid), alcohol abuse, use of coffee at night.
Melatonin is available as dietary supplements and is taken orally during the evening (after dinner) at a dose between 0.5 and 4 mg. Safety profile (when using in short-term) is very good, nevertheless its use in my opinion should always be done under medical indication. Too much in fact we still need to know about this hormone, and everything that comes promote not always correspond to scientific evidence.