Which gland secretes the hormone melatonin?

• A. Thyroid gland
• B. Pineal gland
• C. Adrenal gland
• D. Pituitary gland

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the function of melatonin. Melatonin is a hormone primarily responsible for regulating sleep-wake cycles (circadian rhythms). It is secreted in response to darkness and helps signal the body to prepare for sleep.
2. Step 2: Identify the gland associated with melatonin secretion. Melatonin is secreted by the pineal gland, a small pea-shaped gland located in the brain, specifically in the epithalamus near the center of the brain between the two hemispheres.
3. Step 3: Review the roles of the other glands listed in the options. For example, the thyroid gland regulates metabolism through hormones like thyroxine, the adrenal gland produces stress-related hormones like cortisol and adrenaline, and the pituitary gland is known as the 'master gland' because it controls other glands and secretes various hormones like growth hormone and prolactin.
4. Step 4: Compare the functions of the pineal gland with the function of melatonin. The pineal gland is uniquely responsible for melatonin production, which aligns with its role in regulating circadian rhythms.
5. Step 5: Conclude that the correct answer is the pineal gland, as it is the only gland among the options that secretes melatonin.