PTHLH and neoplasm: When bone metastasis occurs, osteoblasts in the bone microenvironment (BME) secrete calcineurin (CaN) and osteoprotegerin (OPG) [4, 5], and tumour cells secrete parathyroid hormone-related peptide (PTHrP) and interleukin- 6 (IL-6) [6, 7].