What is the Origin of Evening Melatonin Secretion?

This term is central to chronobiology and endocrinology, focusing on the timing of melatonin release, which is the key hormonal marker of the circadian rhythm's transition to the sleep phase. The timing of this "Evening Secretion" is clinically known as the Dim Light Melatonin Onset (DLMO) and is a precise measure of an individual's internal clock.

What is the Mechanism of Evening Melatonin Secretion?

The process is directly regulated by the Suprachiasmatic Nucleus (SCN), the master circadian clock, which receives light information from the retina. As light intensity decreases, the SCN signals the pineal gland to synthesize and secrete melatonin. This hormonal surge then acts on receptors throughout the body, lowering core body temperature and reducing alertness, effectively opening the Deep Sleep Window and initiating the Endogenous Repair Windows.

Evening Melatonin Secretion ∞ Area

Evening Melatonin Secretion

Meaning

Evening Melatonin Secretion is the crucial, chronobiologically-timed release of the hormone melatonin from the pineal gland into the bloodstream, which occurs in response to the diminishing light cues of the late evening. This hormonal signal is the body’s primary chemical messenger for signaling the onset of the biological night, facilitating the initiation of sleep and coordinating the nocturnal phase of the circadian rhythm. Its proper timing and magnitude are essential for sleep quality and systemic repair.