Melatonin – More Than Just a Sleep Hormone


Everybody knows that sleep is good for you, and we can start to feel decidedly ropey if we don’t get enough. However many of us still scrimp on our shut-eye due to work commitments, stress/worry or late nights out on the town. Whilst this can make us feel noticeably run down after a while we don’t tend to give much thought to long term health consequences of sleep deprivation, which it now seems can be very significant. The health issues associated with sleep deprivation appear to be significantly related to a specific hormone that is produced when we are asleep. Research is now showing that this hormone, melatonin, has many roles in the body and is very busy keeping us healthy whilst we dream the night away. However production can easily be disrupted – with a number of worrying consequences that should have you jumping under the covers for a well-deserved kip! Over the next couple of weeks I am going to look at why this hormone is so important and how we can help ensure we produce enough. Enjoy!

Melatonin is produced from the neurotransmitter serotonin (known for inducing a state of calm and happiness) by the pineal gland, which located in the exact centre of the brain. It is the hormone that induces the state of relaxation leading to sleep and many insomniacs are found to be low in this hormone. Melatonin is also secreted by the retina, the gastrointestinal tract, the liver, lungs, skin and certain lymphocytes (immune cells).

Production of this vital hormone is at its highest around puberty (no wonder teenagers are hard to lure from under the duvet before midday!) and remains high through adulthood. Interestingly, production is low in young children (helping to explain the 5 o’clock starts all my friends with kids complain about!). It also declines after 50 years of age, which is thought to be a key reason for increased sleep problems in individuals as they age.

Melatonin is most abundant and active when we are in total darkness and the trigger for melatonin secretion each evening is decreased light exposure. At the end of the day, when sunlight exposure decreases, melatonin is produced, peaking at 2am and declining to half levels by 5am. This close relationship with light and darkness helps explain why we tend to feel much more sleepy on dark winter evenings and more inclined to climb into bed early, whilst in the summer energy levels tend to remain higher for longer and we are more ready to jump out of bed on a sunny morning – it is not just the weather, we are actually programmed to respond to dark and light in this way. Exposure to light (even slight) reduces or halts melatonin production and it takes time for it to increase to normal levels again.

Roles of Melatonin

  • Melatonin has a modulating effect on all the steroid hormones (including the stress hormones cortisol and noradrenalin). It helps reduce high levels of these hormones and also helps modulate levels of neurotransmitters. which affect mood such as serotonin and dopamine. Hence why a good nights sleep is thought to help solve a lot of problems!
  • Immune modulation – immune cells have been found to have specific sites on which melatonin can dock to exert its affects. This can help boost our immune systems capacity to fight invaders and also produce an appropriate inflammatory response.
  • It is a powerful antioxidant
  • Weight maintenance – Studies have shown that the decline in melatonin that occurs with aging causes an increase in body fat, particularly in belly fat. This is probably due to its modulating effects on cortisol levels- as high levels of cortisol cause us to deposit fat around the middle.
  • Regulation of body temperature – Melatonin’s effect on body temperature may be one of the keys of its ability to enhance sleep. Body temperature follows a circadian rhythm, rising during the day and falling at night. In general, a falling body temperature induces sleep, while a rising body temperature provokes wakefulness.
  • Regulation of female hormones – new research is demonstrating that melatonin may influence hormone cycles and be the reason why many mammals go into ‘heat’ at certain times of the year. This affect on hormones has lead to research investigating whether melatonin could reduce the risk of female disorders associated with elevated oestrogen levels such as breast and uterine cancer.

Next time we will look at the health issues associated with imbalanced melatonin levels and how you can help ensure you have just the right amount of this essential hormone.