A parathyroid crisis occurs in patients with severe hypercalcaemia. Parathyroid hormone (PTH) levels are 5-10 times higher than normal and calcium levels are severely high (4 millimoles per litre or above.) The patients are confused and have kidney symptoms (such as kidney stones) and bone symptoms (such as pain). In addition they are usually grossly dehydrated (due to poor kidney function). This collection of symptoms can be completely debilitating.