Summary
A pineal hormone that signals darkness and helps regulate sleep timing.
In depth
The pineal gland makes melatonin from serotonin in darkness under SCN control. It signals night to the body and helps entrain rhythms. Supplements may help jet lag.
Melatonin rises in the evening. Light suppresses it. It has mild sleep-promoting effects.
Example: shift workers may take melatonin to adjust sleep.
Melatonin is made from serotonin by the pineal gland, a small gland deep in the brain, mainly during darkness. Light detected by melanopsin-containing retinal ganglion cells signals the suprachiasmatic nucleus, which controls the pineal; light, especially blue, suppresses melatonin.
Levels rise in the evening, peak in the middle of the night and fall by morning, signalling night to the body and promoting sleepiness, with a mild lowering of body temperature. It helps set circadian and seasonal rhythms: in seasonal breeders, longer nights prolong the melatonin signal and regulate reproduction. Supplements are used for jet lag and some sleep disorders.
Example: using bright screens at night may delay melatonin release.
Remember: it is a darkness hormone, not a sleeping pill.
Frequently asked questions
What is Melatonin?
A pineal hormone that signals darkness and helps regulate sleep timing.
Which area of biology covers Melatonin, and how advanced is it?
Melatonin is one of the 54 topics in Reproduction & Endocrinology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Circadian Endocrinology, Hormones, Hypothalamic-Pituitary Axis.
Can you give an example of Melatonin?
Bright light at night suppresses melatonin.
What should I learn before Melatonin?
Work through the Beginner topics in Reproduction & Endocrinology first, such as Reproduction, Asexual Reproduction, Sexual Reproduction, then return to Melatonin. Intermediate topics assume the Beginner vocabulary.
What topics are related to Melatonin?
The closest topics to Melatonin are Circadian Endocrinology, Hormones, Hypothalamic-Pituitary Axis, Negative Feedback in Endocrine Control. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Melatonin?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Melatonin. To practise the whole of Reproduction & Endocrinology, use the Reproduction & Endocrinology quiz.
How is Melatonin different from Circadian Endocrinology?
Melatonin: A pineal hormone that signals darkness and helps regulate sleep timing. Circadian Endocrinology: Hormone levels follow daily cycles, with cortisol peaking in the morning and melatonin at night. Read both side by side and note what each one explains.
How should I study Melatonin step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Circadian Endocrinology and explain the difference aloud. Finally, take the Reproduction & Endocrinology quiz and come back to this page for any question you miss.