What hormone is produced by the pineal gland?

The hormone produced by the pineal gland is melatonin. Melatonin plays a crucial role in regulating sleep-wake cycles and is influenced by the light-dark cycle in the environment. When it's dark, the pineal gland secretes melatonin, helping to signal to the body that it is time to sleep. Conversely, exposure to light decreases melatonin production, promoting wakefulness during daytime hours. This regulation is essential for maintaining circadian rhythms and overall sleep health.

The production of other hormones such as cortisol, adrenaline, and thyroxine takes place in different glands: cortisol is produced by the adrenal cortex, adrenaline (also known as epinephrine) is produced by the adrenal medulla, and thyroxine is produced by the thyroid gland. Therefore, melatonin is the only hormone among the options listed that is specifically produced by the pineal gland.