Melatoniin

Melatoniin, known in English as melatonin, is a hormone produced mainly by the pineal gland in humans and other vertebrates. It helps regulate the body’s circadian rhythm and sleep–wake cycle. Secretion increases in darkness and decreases with light, contributing to the onset of nighttime sleep.

Synthesis and regulation: Melatoniin is synthesized from serotonin in pinealocytes through the enzymes arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole O-methyltransferase (HIOMT). The pineal gland’s rhythmic activity is driven by the brain’s circadian clock, with higher production at night. Light detected by the retina suppresses melatoniin production via the retinohypothalamic tract to the suprachiasmatic nucleus.

Physiological role and effects: The primary function is the promotion of sleep and the timing of circadian rhythms. Melatoniin also has antioxidant properties and may influence immune function and metabolic regulation. Research into mood effects or other systemic roles is ongoing, but evidence remains varied.

Medical use and safety: In many countries melatoniin is available as a dietary supplement rather than a prescription drug. Doses commonly range from 0.5 to 5 mg taken before bedtime; higher doses are studied but not routinely recommended. Short-term use is generally considered safe, though side effects can include daytime sleepiness, dizziness, and headaches. Potential interactions exist with anticoagulants, diabetes medications, immunosuppressants, and CNS depressants. Caution is advised during pregnancy or lactation and in children; melatoniin should not replace medical treatment for sleep disorders when underlying conditions exist.

Metabolism and pharmacokinetics: Melatoniin is metabolized in the liver, primarily by cytochrome P450 enzymes, and excreted in urine as metabolites such as 6-sulfatoxymelatonin.