褪黑素

title: 褪黑素的产生.
content: 在高等动物中,褪黑素是由松果体中的松果体细胞制造的。松果体产生的褪黑素是内分泌荷尔蒙,会进入血液;视网膜和胃肠道则产生旁泌性荷尔蒙。下丘脑的视交叉上核会由视网膜接收每日光暗的规律,从而影响褪黑素的制造。  在人体内,5-羟色胺(又称为血清素)在N-乙酰基转移酶催化下与乙酰辅酶A反应转化为N-乙酰-5-羟色胺,然后N-乙酰-5-羟色胺再在乙酰血清素O-甲基转移酶催化下被"S"-腺苷甲硫氨酸甲基化为褪黑素。  有些植物,例如稻米,也会制造褪黑素,哺乳类动物进食含有褪黑素的食物后,褪黑素会被吸收,溶入体内的褪黑素。
title: 功效.
title: 生理时钟.
content: 在动物中,褪黑激素参与同步昼夜节律,包括睡眠 - 觉醒时间,血压调节和季节性繁殖。它的大部分作用是激活褪黑激素受体,而另一部分则是它作为抗氧化剂的作用。在植物中,它具有抵抗氧化应激的作用。褪黑激素也存在于各种食物中。但中央神经系统才是控制内分泌系统及旁泌性系统的主要组织(曾经被人误认为褪黑素)。
title: 制造机制.
content: 在正常情况下,由视网膜感知环境中的蓝光亮度,给出的光暗信号传递给松果体,令其在黑暗的情况下制造褪黑素,因此褪黑素亦称「黑暗荷尔蒙」。褪黑素的分泌于晚间中段时间最多,然后在晚间后段时间较少、再随时间逐渐减少至天明。在古代,在温带生活的人于冬季会有十到八小时生活在黑暗当中,而篝火和白炽灯的光中蓝光的成分很少;反之,现代人广泛使用日光灯,身处黑暗的时间减至八小时以下。即使是微弱的灯光下褪黑素的产生都会受到一定程度的影响,在强光下的影响就更大。缺乏褪黑素被认为很可能是夜班工作者得癌病的成因,而现代于晚间亮灯的习惯亦被认为是发达国家越来越多人得癌症的原因之一。

Summary: 褪黑素(英语:melatonin;),或称褪黑激素或美拉托宁,化学名为"N-乙酰基-5-甲氧基色胺",是一种在动物、植物、真菌和细菌中皆有发现的物质。在动物体内,褪黑素是一种调节生物钟的激素;而其作用在其他生物体内可能不同,同样,褪黑素在动物体内的合成过程也不同于其他物种

Melatonin: Melatonin is a hormone that regulates the sleep–wake cycle. It is primarily released by the pineal gland. As a dietary supplement, it is often used for the short-term treatment of trouble sleeping such as from jet lag or shift work. Evidence of benefit, however, is unclear. One review found onset of sleep occurred six minutes faster with use but found no change in total time asleep. It may work as well as the medication ramelteon. It is typically taken by mouth. Side effects from supplements are minimal at low doses for short durations. Side effects may include somnolence (sleepiness), headaches, nausea, diarrhea, and abnormal dreams, irritability, nervousness, restlessness, insomnia (trouble sleeping), anxiety, migraine, lethargy (lack of energy), psychomotor hyperactivity (restlessness with increased activity), dizziness, hypertension (high blood pressure), abdominal pain (stomach ache), dyspepsia (heartburn), mouth ulcers, dry mouth, hyperbilirubinaemia (high blood levels of bilirubin, a breakdown product of red blood cells, which can cause yellowing of the skin and eyes), dermatitis (skin inflammation), night sweats, pruritus (itching), rash, dry skin, pain in the extremities (arms and legs), symptoms of the menopause, asthenia (weakness), chest pain, glycosuria (sugar in the urine), proteinuria (protein in the urine), abnormal liver function tests, increased weight, tiredness, mood swings, aggression and feeling hungover. Use is not recommended during pregnancy or breastfeeding. Use is also not recommended in those with liver problems. In animals (including humans), melatonin is involved in synchronizing the circadian rhythm including sleep–wake timing, blood pressure regulation, and seasonal reproduction. Many of its effects are through activation of the melatonin receptors, while others are due to its role as an antioxidant. In plants it functions to defend against oxidative stress. Melatonin is also present in various foods. Melatonin was discovered in 1958. It is sold over the counter in Canada and the United States; in the United Kingdom it is a prescription-only medication. It is not approved by the US Food and Drug Administration (FDA) for any medical use. In Australia and the European Union it is indicated for trouble sleeping in people over the age of 54. In the European Union it is indicated for the treatment of insomnia in children and adolescents. It was approved for medical use in the European Union in 2007.