<qa>  What is the cause of primary hyperparathyroidism?Primary hyperparathyroidism PHPT is a common disease that occurs in 1 in 10,000 people every year. In the presence of this condition, the parathyroid glands produce excessive amounts of parathyroid hormone PTH, which regulates calcium levels. The high levels of parathyroid hormone remove too much calcium from bones, and then deposit the excess calcium in the blood, which is then filtered into the urine by the kidneys. Bone health is threatened by excess calcium loss which weakens bone structure. Other affected organs include the skeleton calcium loss leads to a weakening of the skeleton, and the kidneys high blood calcium can lead to kidney stones. 