Final answer:
Parathyroid hormone (PTH) is the antagonist of calcitonin, working in opposition by affecting calcium levels.
Explanation:
Parathyroid hormone (PTH) is an antagonist of calcitonin. PTH works in opposition to calcitonin by promoting the release of calcium from bones into the blood, increasing calcium levels in the blood. On the other hand, calcitonin inhibits osteoclast activity and stimulates calcium excretion by the kidneys, reducing blood calcium levels.
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