Why Melatonin May Be More Than a Sleep Hormone: Its Role in Mitochondrial Repair

Melatonin is best known as the hormone that signals bedtime, but this review makes the case that its job doesn't stop at sleep onset. The authors synthesise a growing body of evidence that melatonin is actually synthesised, transported and used directly inside mitochondria themselves, where it supports what researchers call 'mitochondrial quality control', the ongoing housekeeping process of building new mitochondria, repairing damaged ones, and clearing out those beyond repair (a process called mitophagy). The review describes how melatonin helps restore the balance between mitochondria fusing together and splitting apart, a balance that's disrupted in ageing and poor sleep, and how it supports the recovery of energy production after cellular stress. As a review of preclinical and mechanistic literature rather than a clinical trial, this doesn't establish that taking melatonin supplements will improve mitochondrial health in people, and the authors are focused on disease models rather than healthy ageing. What it does offer is a plausible biological bridge explaining why consistently poor sleep, which disrupts natural melatonin rhythms, might show up as measurable cellular wear over time.