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Overview of the Endocrine System

Author(s): Center for Educational Outreach, Baylor College of Medicine.

Pineal Gland

The pineal gland is a small mass of tissue near the center of the brain. It secretes the hormone melatonin, which regulates functions related to light and seasons that are marked by changes in daylight. Melatonin affects skin pigmentation, but most pineal gland functions are related to biological rhythms associated with reproduction. Melatonin is secreted at night, with the amount secreted directly related to the length of the night.