The pineal gland: From last to first

The human pineal gland is a highly active organ of internal secretion which synthesizes and secretes an important time-giving hormone on a nightly basis. Among many functions, the exclusive nighttime production of melatonin provides important time-of-day and time-of-year information to other organs in the body. Furthermore, melatonin likely influences critical endocrine events such as puberty as well as altering reproductive physiology after adulthood. The consequences of excessive (hypermelatoninism) and reduced (hypomelatoninism) melatonin secretion are summarized herein. Whereas some of the actions of melatonin involve specific membrane-bound receptors for the hormone, other actions of melatonin likely do not rely on classic membrane receptors. Melatonin in highly lipophilic and gains ready access to every fluid and tissue in the body. The hormone likely has ubiquitous actions. The argument is made in thii brief review that every field of medicine may benefit from knowledge related to the function of the pineal gland.