A Reproductive Lexicon


Ownership of this website has been transferred from Northwestern University to Michigan State University.
Please note that some site information may be inaccurate while adjustments to reflect this organizational change are made.

MOOC Advertisement

Learn More:
Get An Introduction to Reproduction

Learn more about the science of reproduction. Dr. Teresa Woodruff, creator of Repropedia, is offering a free online course exploring the world of reproduction.

Get Started!


Melatonin is a chemical found in the human body and is part of the biological machinery that regulates the sleep-wake cycle of an individual over the course of a day. It is also found in other living species, including animals, plants, and microorganisms. In humans, high levels of melatonin are secreted by the pineal gland at night, which causes drowsiness. Medications containing melatonin have been used to treat jet lag and insomnia, although efficacy is still debatable.