Answer: pineal gland.
- A pineal gland
- B thyroid gland
- C adrenal gland
- D pancreas
Correct answer: A. pineal gland
Explanation: The pineal gland secretes melatonin, influencing sleep patterns.
The hypothalamus releases hormones that direct the pituitary, which releases its own trophic hormone to a target gland; that gland's hormone output then feeds back (dashed lines) to suppress both the pituitary and hypothalamus once levels are sufficient - a self-correcting loop running the entire endocrine system.
Concept context
The endocrine glands, hormone classification and mechanism of action, and negative feedback regulation.