First, it is the center for the production of the hormone melatonin. Melatonin is implicated in a wide range of human activities. Melatonin is released in the dark, during sleep. Melatonin is a very ancient hormone that is found throughout the animal kingdom. In these animals, the pineal gland is the master clock.
Light severely curtails the production of melatonin.
Melatonin has been shown to inhibit the growth and metastasis of some tumors in experimental animals, and may therefore play a role in cancer inhibition. Patients who have breast cancer have lower levels of melatonin in the blood. The hormone has also been shown to be protective against genetic damage, and it has a stimulatory effect on the immune system. The anticancer role of melatonin in humans is not established yet, but in a study involving blind women, melatonin production was found to be higher at all times. This finding was associated with the finding that breast cancer in this study was correspondingly lower for these blind women compared to the general population.