os·te·o·cal·cin 
(ŏs′tē-ō-kălsĭn)
(ŏs′tē-ō-kălsĭn)n.
A calcium-binding substance produced by osteoblasts that is essential to bone mineralization and can be used as a biomarker for osteoporosis. It may also act as a hormone to increase insulin production and insulin sensitivity.