Mature osteoclasts will also express the calcitonin receptor upon its surface, which has been known for decades as a prominent negative controller of bone resorption (9) . Calcitonin receptors are of the G proteincoupled receptor family (comprising seven transmembranespanning receptor domains) whose signaling will inhibit osteoclast activity both in vitro and in vivo (10) . Calcitonin receptor activation upon osteoclasts, by its ligand calcitonin, will rapidly induce the loss of ruffled border and immobility followed by cell retraction and arrest of bone resorption. Calcitonin receptor signaling will also alter ion transporter distribution, impair enzyme activity (11) and inhibit the osteoclastogenic effects of RANKL (12) .