Which gland in the brain produces melatonin?

The pineal gland is the gland in the brain that produces melatonin. This small endocrine organ helps the body coordinate its sleep–wake cycle with the daily pattern of light and darkness.

The pineal gland sits near the center of the brain, in a region called the epithalamus, between the two halves of the thalamus. It is only about 5–8 millimeters long in humans and has a pine-cone-like shape, which explains the origin of its name. Its main hormone, melatonin, is produced primarily in darkness and released in a daily rhythm.

Light detected by the retina travels through a neural pathway to the suprachiasmatic nucleus, the brain’s central circadian clock. Signals then pass through the hypothalamus and sympathetic nervous system to the pineal gland. Darkness removes this inhibition, allowing melatonin production to rise at night.

The pineal gland is often confused with the pituitary gland or hypothalamus. Those structures help regulate many hormones and body functions, but they do not serve as the brain’s primary source of melatonin. Yale researcher Aaron B. Lerner and colleagues isolated and named melatonin in 1958.