Pinealocytes

Pinealocytes are the primary secretory cells of the pineal gland. They synthesize and secrete the hormone melatonin in a circadian rhythm, with levels high at night and low during the day. Melatonin regulation is controlled by light input from the suprachiasmatic nucleus via a sympathetic pathway. Melatonin helps synchronize the body's sleep-wake cycle (circadian rhythm) and seasonal reproductive functions.