When the blood calcium is too low PTH is released to bring the calcium level back up to normal. When the calcium level is normal or gets a little too high, normal parathyroid glands will stop releasing PTH. Proper calcium balance is crucial to the normal functioning of multiple body systems and in particular the heart, nervous system, kidneys and bones.
Symptoms of PHPT can vary to a degree based usually on the length of time it has remained untreated. By the time many people are diagnosed due to symptoms, they will have had PHPT for some time.