What happens when your parathyroid hormone shuts off completely?

Cardiac arrhythmia: While this is most unlikely, parathyroid hormone is one of the major controls of calcium metabolism and homeostasis. But, vitamin d and calcitonin are also involved. Therefore, even if all of your parathyroid glands are removed, you would develop symptoms over a short time--which the other mechanisms try to compensate. But, short answer: you get a cardiac arrhythmia and could die.