What is the Origin of Melatonin Secretion?

The term combines "melatonin," a hormone first isolated and named for its ability to lighten skin pigment in certain animals, with "secretion," the process of producing and discharging a substance. Its role as the primary hormone of darkness was elucidated through decades of chronobiological research. The pineal gland's function as a neuroendocrine transducer of light-dark cycles is a core concept in this field.

What is the Mechanism of Melatonin Secretion?

Melatonin synthesis and secretion are controlled by the suprachiasmatic nucleus (SCN) of the hypothalamus, the body's central clock, which receives light information from the retina. In darkness, the SCN signals the pineal gland via the sympathetic nervous system to increase the activity of the enzyme N-acetyltransferase (NAT). NAT is the rate-limiting enzyme that converts serotonin to N-acetylserotonin, which is then converted to melatonin, leading to its characteristic nocturnal surge in the blood.

Melatonin Secretion

Meaning

Melatonin Secretion is the process by which the pineal gland, a small endocrine gland in the brain, releases the hormone melatonin into the systemic circulation. This release is highly rhythmic, characterized by a distinct nocturnal peak and minimal daytime levels, thereby encoding the circadian signal of darkness. The primary function of this secretion is to regulate the sleep-wake cycle and influence the timing of other circadian rhythms.