Final answer:
Calcitonin secretion is stimulated by high calcium ion concentrations in the blood. The effector functions of calcitonin are to inhibit osteoclast activity in the bones and stimulate calcium excretion in the kidneys.
Step-by-step explanation:
Calcitonin secretion is stimulated when calcium ion concentrations in the blood rise.
The effector functions of calcitonin (CT) are to inhibit osteoclast activity in the bones and stimulate excretion of calcium in the kidneys. These actions work together to lower body fluid levels of calcium and help regulate calcium concentrations in body fluids.