Melatonine

Melatonine is a hormone produced primarily by the pineal gland in humans and other vertebrates. Its secretion follows a roughly 24-hour cycle, rising after dusk, peaking during the night, and falling toward morning. Light exposure detected by the retina influences this cycle through the suprachiasmatic nucleus, which signals the pineal gland to adjust melatonine production.

Biochemistry: Melatonine is synthesized from serotonin via acetylation by AANAT and methylation by ASMT. It acts on melatonin receptors MT1 and MT2, with MT3 as a less clearly defined target, and may also exert receptor-independent antioxidant effects.

Physiological roles: The primary function is to help regulate sleep-wake timing (a chronobiological signal for night). It also has antioxidant properties and may modulate immune responses and seasonal physiology in some species.

Clinical use: Melatonine is available as an over-the-counter supplement in many countries and is used to address jet lag, shift-work sleep disorder, and some forms of insomnia. Dosing typically ranges from 0.5 to 5 mg taken before intended sleep, but recommendations vary. Long-term safety data are limited, and side effects—drowsiness, headache, dizziness—can occur. Interactions with alcohol, anticoagulants, diabetes medications, and immunosuppressants are possible.

Pharmacokinetics and regulation: Oral melatonine is absorbed with peak levels about 60 minutes after ingestion; half-life is short, often cited as 30 to 60 minutes, with substantial individual variation. The hormone is available as a supplement in many jurisdictions, but its use for medical treatment should be guided by a healthcare professional, particularly in children, pregnant individuals, or people with chronic illnesses.