This article waslast modified on 10 July 2017.
A condition characterised by an overproduction of parathyroid hormone (PTH), a hormone that controls calcium and phosphate levels in blood and calcium in bone; it is made by the parathyroid glands. Primary hyperparathyroidism causes high calcium and low phosphate levels, and can cause kidney stones occasionally. Secondary hyperparathyroidism is caused by low levels of calcium or vitamin D, or high levels of phosphate; it is commonly caused by chronic kidney disease. Either form can cause osteoporosis or bone pain.