Melatonin褪黑素 · Melatonin

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全球年销 $1.5B+ · 天然睡眠激素营销 · 但商业剂量 5-10 mg 远超有效剂量 0.3 mg · 真适应症窄

Pineal synthesis · dark signal

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松果体合成 · 黑暗信号

Melatonin is the body's own 'nighttime signal' hormone, secreted mainly by the pineal gland deep in the brain.

Synthesis chain: Tryptophan → 5-hydroxytryptophan → serotonin (5-HT) → N-acetylserotonin → melatonin. The key enzyme is AANAT (aralkylamine N-acetyltransferase), regulated by the circadian clock.

The control switch is the suprachiasmatic nucleus: The brain's master clock — set by light, it runs the body's day–night rhythm. (suprachiasmatic nucleus): retinal ipRGCs (containing melanopsin) sense blue light (~480 nm). During the day the SCN suppresses AANAT and melatonin is low; in darkness the SCN releases suppression, AANAT is upregulated, and melatonin surges.

Typical rhythm:

Daytime plasma <10 pg/mL9–10 pm starts rising (Dim Light Melatonin Onset, DLMO)2–4 am peak ~80–200 pg/mL (higher in children, much lower in the elderly)Returns to baseline by 6–7 am
Real role in sleep chemistry

Melatonin doesn't directly make you fall asleep — it signals to the body that 'it's now night'. Sleep itself is the combined effect of adenosine, sleep pressure, and the circadian clock. Melatonin's actual job is phase-shifting the body clock, dropping core temperature 0.3–0.5°C, and weakening the wake drive.

What aging and modern life do to it

After age 30, peak melatonin drops ~10–15% per decade — a 70-year-old has only one-third of a 25-year-old's peak. Modern blue-light exposure (phones, computers, LEDs) does the same: 1–2 hours of evening screen time can delay DLMO 1–3 hours and lower peak amplitude 20–50%. This explains why modern people have widely disrupted sleep rhythms, why the elderly struggle to fall asleep, and why blue-light glasses or phone night mode actually make sense.

One common misconception: 'more serotonin = better sleep' is only half right. Serotonin is melatonin's precursor, but supplementing serotonin or tryptophan alone won't significantly raise melatonin, because other regulatory steps gate the path.

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