Fig. 1. Schematic summary illustrating the relationship between calcium and diabetes. Hyperparathyroidism is related to long-term insulin resistance and relative insulin insufficiency and can lead to overt diabetes mellitus (DM) or deterioration of glycemic control in established DM. Patients with DM have an increased risk for development of acute renal failure due to volume depletion. In particular, parathyroid hormone (PTH) secretion in DM patient tends to decrease. Disrupted calcium homeostasis facilitates renal failure. In DM patients, cellular calcium depletion occurs. In type 1 DM, not only is there diminishment of pancreatic β cells, but both intracellular and intra-endoplasmic reticulum (ER) calcium are depleted. In type 2 DM intra-ER calcium is depleted, which induces ER stress.