Answer: Calcitonin.
- A Calcitonin
- B Thyroxine
- C Glucagon
- D Parathyroid hormone
Correct answer: A. Calcitonin
Explanation: Calcitonin, secreted by the thyroid gland, lowers blood calcium by reducing its release from bone.
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.