Intrinsically synthesized melatonin in mitochondria and factors controlling its production.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic and evolutionary concepts without empirical trial data or meta-analysis.
PubMed 38920277 · doi:10.14670/HH-18-776
What was done
Narrative review evaluating the distinction between pineal and extrapineal (primarily mitochondrial) melatonin synthesis, its evolutionary conservation across organisms lacking a pineal gland (plants, protists, invertebrates), and its localized intracellular functions in vertebrates.
What was found
The pineal gland produces a small fraction (likely <5%) of total vertebrate melatonin, which functions cyclically as an endocrine signal impacting the suprachiasmatic nucleus and clock genes. Extrapineal melatonin, primarily synthesized in mitochondria, accounts for the remaining majority; its synthesis is non-circadian, independent of photoperiod, and not typically released into systemic circulation. Instead, it acts locally or via paracrine signaling to maintain redox homeostasis and neutralize free radicals. The abstract provides no primary experimental datasets or statistical analyses.
Why it matters
Highlights that the bulk of vertebrate melatonin acts as a local mitochondrial antioxidant and homeostatic regulator rather than purely as a circadian hormone, reframing its biological role beyond sleep and rhythm regulation.
Limits
The paper is a narrative overview without primary empirical human or animal data, systematic review methodology, or quantitative synthesis. As noted in the abstract, the regulatory mechanisms governing extrapineal melatonin production remain largely undefined.
Cited by
- supports Melatonin is present in cells throughout the body where its production is not suppressed by light and functions as an antioxidant.