Major component of the eggshell matrix. May play an important role in the regulation of calcite growth during eggshell calcification. May also regulate the mineralization process in developing and growing bones. Synthesized and secreted by the granular epithelial cells of the uterus and incorporated into the eggshell matrix. In the eggshell, expressed mainly in the palisade and mammillary layers. Expression also detected in the hypertrophic zone of the epiphyseal growth plate, and in cortical and medullary bone (at protein level). Highly expressed in uterus. Not detected in the proximal oviduct, liver, magnum, duodenum and kidney. Expressed at high levels at the middle of the calcification stage of shell formation. Expression levels are similar at 3-4 hours post-oviposition prior to entry of the egg into the uterus and at 16-17 hours post-oviposition during eggshell calcification. Expressed in tibia from E5 and in mandible from E7 until the end of embryonic development at E19. Expression detected first in osteoblasts, in later stages both in osteoblasts and osteocytes, and by the end of embryonic development mainly in osteocytes. Asn-62 is fully glycosylated, whereas only less than 10% of Asn-293 seem to be glycosylated. Belongs to the osteoregulin family.