[Clinical approach to patients with hypocalcemia].

Serum calcium (Ca) level is tightly regulated by parathyroid hormone (PTH) and 1,25-dihydoxyvitamin D in human. In practice, however, one should take a look at background factors that have significant effects on Ca and its regulating hormones. Among them vitamin D insufficiency, magnesium (Mg) depletion and treatment with bisphosphonates, glucocorticoids and anticonvulsants are most important.