Melatonin is a neuroendochrine hormone regulating biological rhythms, secreted from the pituitary at night, in proportion to the duration of darkness. The actions of melatonin are mediated by specific membrane receptors, MT1 and MT2, expressed in the CNS (hippocampus, cerebellum, pars tuberalis of the pituitary gland) and in some peripheral organs (mammary epithelium, uterine myometrium, ovarian granulosa and luteal cells).
The literature has provided evidence that melatonin plays a role in the seasonality of conception, with a peak in winter-spring transition, when there is a reversed relationship between melatonin levels (low) and ovarian activity (high). Other studies have shown the correlation between high levels of melatonin and low plasma concentrations of FSH and LH in women in primary and secondary amenorrhea, in subjects in pubertal age, and in blind boys; this correlation seems to permit the conclusion that melatonin acts as an inhibitor of the hypothalamic-pituitary-gonadal axis, with reduction of the GnRH gene expression. Melatonin also regulates the secretion of sex steroids and protects the ovarian follicles from oxidative stress and the oocytes from free radicals.
The role of melatonin in human pregnancy is still not clear: a reduction of its levels, secondary to day-night cycle disorders or to prolonged exposure to light even at night, could be a possible cause of some complications of pregnancy, such abortion, preeclampsia, and neonatal neurological disability. Reduced melatonin production in early pregnancy may be related to the development of spontaneous abortions; similar low levels of melatonin are found in pregnancies complicated by preeclampsia, suggesting its role in the pathogenesis due to an increased oxidative stress on the placenta, induced initially by the production of cytotoxic factors and by the consequent production of free radicals. Moreover, melatonin appears to play regulatory role in blood pressure, exposing those with low levels to a greater risk of developing preeclampsia. Of recent acquisitions is its synergism with oxytocin to intensify uterine contractility in labor.
In conclusion, melatonin seems to be essential during pregnancy, because it acts not only as a regulator of circadian rhythms, but also as endocrine modulator, immunomodulator, "scavenger" of free radicals, and indirectly as an antioxidant and cytoprotective agent, as well as enhancing the contractility of the uterus in labor in synergy with oxytocin. Treatment with melatonin may have a wide range of benefits. Currently, because of the lack of clinical data, it is not recommended for use during pregnancy or preconception period, although animal studies have not shown any direct or indirect harmful effects on pregnancy, embryo-fetal and / or postnatal development.
Bibliography
-Takayama H, Nakamura Y, Tamura H et al. Pineal gland (melatonin) affects the parturition time, but not luteal function and fetal growth in pregnant rats. Endocr J. 2003 Feb; 50 (1) :37-43
-Tauman R, Zisapel N, Laudon M et al. Melatonin production in infants. Pediatr Neurol 2002, 26 (5) :379-82
-Jauniaux E, Hempstock J, Greenwold N et al. Trophoblastic oxidative stress in relation to temporal and regional differences in maternal placental blood flow in normal and abnormal pregnancies. Am J Pathol 2003; 162 (1) :115-25
-Escames G, Khaldy H, León J et al. Changes in iNOS activity, oxidative stress and melatonin levels in hypertensive patients treated with Lacidipine. J Hypertens 2004, 22 (3) :629-35
-Sharkey JT, Puttaramu R, Word RA, et al. Melatonin synergizes with oxytocin to enhance contractility of human myometrial smooth muscle cells. J Clin Endocrinol 2009 Feb; 94 (2) :421-7
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Melatonin is a neuroendochrine hormone regulating biological rhythms, secreted from the pituitary at night, in proportion to the duration of darkness. The actions of melatonin are mediated by specific membrane receptors, MT1 and MT2, expressed in the CNS (hippocampus, cerebellum, pars tuberalis of the pituitary gland) and in some peripheral organs (mammary epithelium, uterine myometrium, ovarian granulosa and luteal cells). 
In a study of 2511 patients that switched from atorvastatin to simvastatin, after they had used atorvastatin for at least 6 months, were compared to a control group of 9009 patients who had made no switch.
There was a statistically significant increase in the risk of death, as well as of stroke and major cardiovascular events associated with the switch to a different statin.
This finding may...
The discovery of penicillin is associated to the name of Alexander Fleming, who in 1928 noticed the inhibition of growth of a bacterium from a mold. But it was not until 1940 that the studies by Fleming, Florey and Chain allowed the isolation of Penicillin, which was later successfully used to help the many wounded soldiers during the Second World War. In 1945 Fleming, Florey and Chain were...
The management oral anticoagulant therapy (OAT) is of great importance for family doctors, because there are many people with venous thromboembolism, or various cardiovascular diseases, such as myocardial infarction and stroke, who are at great risk for embolism.
Oral anticoagulant therapy (OAT), is designed to depress in a controlled and reversible manner blood coagulability, which is measured...
Endometriosis is a common and complex gynecological condition, yet little known, despite involving 150 million women worldwide (14 million in Europe and 3 million in Italy). In addition to interfering with the physical well being, it can also have important repercussions on the psyche, on the couple's relationship, and on the social and working life of those affected. It is estimated that...
