What is the importance of pineal gland?

Pineal gland produces melatonin hormone. This hormone is important to maintain the sleep patterns and maintain the photoperiodic functions. Pineal gland appears to play a major role in sexual development, hibernation in animals, metabolism, and seasonal breeding. Melatonin levels are high at night and low during the day. Melatonin has important effects in integrating photoperiod and affecting circadian rhythms. Hence it has significant effects on reproduction, sleep-wake cycles and other phenomena showing circadian rhythm.