Hello and welcome to the Zero to Finals podcast. My name is Tom and in this episode

I'm going to be talking to you about melatonin. And you can find written notes on this topic

at zero to finals.com slash melatonin or in the 0 to finals endocrine system book.

And you can find flashcards and questions to train your knowledge on this content and

help you remember the information for longer at members.0 to finals.com. So let's get straight into it.

Melatonin is a hormone released by the pineal gland, which is a pea-sized gland located in the

center of the brain. It plays an important role in controlling the circadian rhythm and the

sleep-wake cycle. There's a relationship between light

exposure and melatonin. Exposure to bright light, for example in the morning, reduces melatonin,

and the levels rise in dark environments, for example at night time. Let's go through some clinical

relevance. Exposure to light in the evening strongly suppresses melatonin, resulting in difficulty

falling asleep and a phase shift in the sleep pattern, with a later onset of sleep and difficulty waking early in the morning.

Delayed sleep phase syndrome, or DSPS, involves an onset of sleep and waking more than

two hours later than desired. Let's go through the function of melatonin. Melatonin promotes the onset of sleep. The levels

rise in the evening, peak in the middle of the night and fall in the morning and remain

low during the day. Melatonin receptors, MT1 and MT2, are found throughout the body.

Notably, they're found in the suprakiasmatic nucleus, which is a structure in the anterior

hypothalamus responsible for circadian rhythm.

In addition to promoting sleep and controlling circadian rhythm, it also helps

lower the body temperature and lower the blood pressure. Let's talk about disruption. Disruption

to melatonin and the circadian rhythm may occur with delayed sleep phase syndrome, or DSPS, shift work, for example,

variable working hours between night and day shifts, jet lag, seasonal effective disorder

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