The body's reaction to PTH (parathyroid hormone), a reduction in plasma levels of calcium, can be opposed by Naim 00:45 AP Biology Chapter 32 The body's reaction to PTH (parathyroid hormone), a reduction in plasma levels of calcium, can be opposed by A) thyroxine. B) calcitonin. C) growth hormone. D) epinephrine. E) glucagon. Answer: B Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+