History of the pineal gland

The history of the pineal gland is an account of the scientific development on the understanding of the pineal gland from the ancient Greeks that led to the discovery of its neuroendocrine properties in the 20th century CE. As an elusive and unique part of the brain, the pineal gland has the longest history among the body organs as a structure of unknown function – it took almost two millennia to discover its biological roles. Until the 20th century, it was recognised with a mixture of mysticism and scientific conjectures as to its possible nature.

The ancient Greeks visualised the pineal gland as a sort of guard (valve), like the pylorus of stomach, that regulate the flow of pneuma (vital spirits) in the brain. Galen of Pergamum in the 2nd century CE was the first to make written record of the gland and argued against the prevailing concept. According to him, the gland has no spiritual or physiological role, but merely a supporting organ of the brain, and gave the name κωνάριο (konario, often Latinised as conarium) for its cone-shaped appearance. Galen's description remained a scientific concept until the Renaissance when alternative explanations were postulated. By then, the Latin name glandula pinealis became a common usage. René Descartes's description as the "seat of the soul" in the 17th century became one of the most influential concepts for the next three centuries.

The biological role of the pineal gland was first discovered in 1958 when dermatologist Aaron B. Lerner and colleagues discovered a skin-lightening factor, which they named melatonin. Lerner's team found the chemical compound from the cow pineal extract that could lightens the skin of frog. It was subsequently discovered that melatonin is a hormone that regulates day-night cycle (circadian rhythm), and modulates other organs. The pineal gland thereby was established as an endocrine gland. As it controls other the important endocrine glands, including the so-called "master gland", the pituitary gland, it is more appropriate to refer the pineal gland as the true "master gland" of the body.