PTH and bone neoplasm: Paraneoplastic causes of HC include: ectopic production of parathyroid hormone (PTH) or PTH‐related peptide (PTH‐rP), extensive and usually multifocal lytic bone tumours, tumour associated prostaglandins (PGE1 and PGE2), interleukin 1‐ β, transforming growth factor –β (TGF‐ß) and receptor activator of nuclear factor kappa‐ β ligand (RANKL) (Bergman 2013).