Dual sources of melatonin and evidence for different primary functions.
Level 5 - mechanism / opinion, no new human data
Narrative review and mechanistic theoretical reasoning without original human data
PubMed 38808108 · doi:10.3389/fendo.2024.1414463
What was done
Narrative review synthesizing data and conceptual frameworks regarding two distinct biological sources and functional pathways of melatonin in mammals, including humans: pineal versus extrapineal tissue synthesis.
What was found
No primary experimental data, effect estimates, or statistical results are reported in the abstract. The authors speculate that the pineal gland produces less than 5% of total mammalian melatonin in a circadian rhythm released into blood and cerebrospinal fluid for central and peripheral clock regulation. The remaining majority is proposed to be synthesized locally within mitochondria of peripheral tissues in a non-circadian pattern to maintain cellular redox homeostasis and metabolic function.
Why it matters
This review differentiates systemic circadian signaling from local cellular antioxidant mechanisms, providing a theoretical framework for distinct physiological roles of melatonin pools.
Limits
As a narrative review, it presents mechanistic theory and speculation rather than novel empirical or clinical data. Regulating factors and synthesis mechanisms for extrapineal melatonin remain unknown.
Cited by
- supports Melatonin is present in cells throughout the body where its production is not suppressed by light and functions as an antioxidant.