Answer: hormones.
- A hormones
- B enzymes
- C vitamins
- D antibodies
Correct answer: A. hormones
Explanation: Hormones are chemical messengers that coordinate body functions.
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.