The regulatory effect of PTH on bone is well established while biological active substances released from bone with a regulatory function on parathyroid cells are emerging. The crosstalk between bone and parathyroid cells occurs by means of the phosphaturic hormone FGF23, released from osteoblasts/osteocytes, and leptin, released from adipocytes and osteoblasts. Parathyroid cells express the specific receptor for FGF23, FGF receptor/a-Klotho complex, and for leptin. Here, we identified osteocalcin as a further hormone potentially involved in the crosstalk between bone and parathyroid cells, demonstrating that human parathyroid cells express the osteocalcin receptor GPRC6A and respond to stimulation with increasing concentrations of osteocalcin in term of modulation of the ERK and AKT pathways.