[Calcium homeostasis and diabetes mellitus]

Diabetes mellitus is associated with various organ dysfunctions through hyperglycemia, insulin deficiency, or advanced glycation end products, which can also cause impaired calcium homeostasis such as the reductions of parathyroid hormone secretion, vitamin D receptor (VDR) number, and 25- (OH) vitamin D-1 alpha-hydroxylase activity in the parathyroid gland, intestine, and kidney, respectively. On the contrary, abnormal calcium homeostasis such as vitamin D deficiency/insensitivity and hyperparathyroidism can cause glucose intolerance or diabetes. Vitamin D deficiency/insensitivity induces type 2 diabetes through impaired insulin secretion involving VDR on pancreatic beta cells, as well as type 1 diabetes through the reduction in immuno-modulatory action of 1,25 (OH)(2) vitamin D. Primary hyperparathyroidism induces glucose intolerance via insulin resistance due to elevated intracellular calcium in the targeted organ of insulin.