In mammals, the pineal gland is the sole endocrine source of melatonin, which is secreted according to daily and seasonal patterns. This mini-review synthesizes the established endocrine actions of melatonin in the following temporal contexts. Melatonin is a strictly regulated output of the circadian timing system, but under certain conditions, may also entrain the circadian pacemaker and clocks in peripheral tissues. As the waveform of nightly melatonin secretion varies seasonally, melatonin provides a hormonal representation of the time of year. The duration of elevated melatonin secretion regulates reproductive physiology and other seasonal adaptations either by entraining a circannual rhythm or by inducing seasonal responses directly. An entrainment action of nightly melatonin on clock gene expression in the pars tuberalis of the anterior pituitary may partly underly its mechanistic role as a photoperiodic switch. Melatonin has important functions developmentally to regulate multiple physiological systems and program timing of puberty. Endogenous melatonergic systems are disrupted by modern lifestyles of humans through altered circadian entrainment, acute suppression by light and self-administration of pharmacological melatonin. Non-endocrine actions of locally synthesized melatonin fall outside of the scope of this mini-review.

中文翻译：

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哺乳动物中松果体褪黑激素信号传导的时间组织。

在哺乳动物中，松果体是褪黑激素的唯一内分泌来源，褪黑素是根据日常和季节性方式分泌的。这份简短的综述综合了褪黑激素在以下时间范围内已确立的内分泌作用。褪黑激素是昼夜节律计时系统的严格调节输出，但在某些条件下，褪黑素也可能会带动昼夜节律起搏器和周围组织中的时钟。由于夜间褪黑激素分泌的波形随季节变化，因此褪黑激素可提供一年中某个时间的荷尔蒙代表。褪黑激素分泌增加的持续时间通过夹带一个昼夜节律或直接诱导季节性反应来调节生殖生理和其他季节性适应。夜间褪黑激素对垂体前叶结节中时钟基因表达的诱使作用可能部分地是其作为光周期开关的机械作用。褪黑激素在发育中具有重要的功能，以调节多个生理系统和青春期的程序时间。内在的褪黑素能系统通过改变人类的昼夜节律，光的急性抑制和药理褪黑素的自我管理而被人类的现代生活方式所破坏。局部合成的褪黑激素的非内分泌作用不在本综述的范围之内。内在的褪黑素能系统通过改变人类的昼夜节律，光的急性抑制和药理褪黑素的自我管理而被人类的现代生活方式所破坏。局部合成的褪黑激素的非内分泌作用不在本综述的范围之内。内在的褪黑素能系统通过改变人类的昼夜节律，光的急性抑制和药理褪黑素的自我管理而被人类的现代生活方式所破坏。局部合成的褪黑激素的非内分泌作用不在本综述的范围之内。