Melatonin-SRItem Description Sustained release melatonin to support healthy sleep* Melatonin SR provides sustained release MicroActive melatonin to promote healthy sleep. Melatonin is a hormone produced by the pineal gland, which regulates the body's sleep wake cycle. Melatonin's primary role is regulation of the body's circadian rhythm, endocrine secretions, and sleep patterns. Studies indicate that it facilitates the onset of sleep, as well as sleep efficiency.