The excess amounts of parathyroid hormone act on the kidney, bones, and vitamin D metabolism to raise blood calcium levels. Patients often get osteoporosis, kidney stones, and a number of different symptoms of the high calcium including fatigue, weakness, excessive urination, dehydration, depression, and abdominal pain. A small proportion of patients with pituitary tumors have an inherited defect in a gene that can also cause hyperparathyroidism. This condition is called MEN-1. Patients may also get pancreatic tumors that produce insulin or gastrin.