PTHLH and neoplasm: During bone metastasis, invading tumour cells disrupt the normal bone remodelling process over time by releasing growth factors, most notably PTHrP, that activates osteoclasts to collaborate and resorb the bone matrix and releasing chemotactic stimuli and additional growth factors (TGFβ, Ca2+) (Yoneda et al., 1994; Guise, 2002; Kumar and Weaver, 2009).