Which hormone is produced by the pineal gland?

• A. Melatonin
• B. Prolactin
• C. Cortisol
• D. Growth hormone

Answer: (A)

Melatonin is the hormone produced by the pineal gland. It helps regulate the sleep-wake cycle, with levels rising in darkness and falling with light. This rhythmic release is driven by the brain’s circadian clock (the suprachiasmatic nucleus) and the sympathetic nerves that innervate the pineal gland, which signal the gland to increase melatonin production at night from serotonin. Prolactin, cortisol, and growth hormone are produced by other glands (prolactin and growth hormone by the pituitary, cortisol by the adrenal cortex), so they don’t originate from the pineal gland.