Parathyroid Cells Are Inhibited from Synthesizing and Releasing Parathyroid Hormone

Multiple Choice

Parathyroid cells are inhibited from synthesizing and releasing parathyroid hormone (PTH) when circulating calcium levels are high.When calcium levels fall, the inhibition is removed, PTH is synthesized and released, and calcium levels rise in the blood until the parathyroid cells are once again inhibited.This process is an example of

A) negative feedback.
B) induction.
C) downregulation.
D) upregulation.
E) positive feedback.