Background Parathyroid hormone-like hormone (PTHLH) was initially identified as the tumor product that is responsible for most instances of humoral hypercalcemia of malignancy.PTHLH regulates cell growth and differentiation, bone development and lactation, embryonic and fetal development and survival, morphogenesis, and placental calcium transport via intracellular, paracrine and endocrine pathways. The parathyroid hormone (PTH) and PTHLH genes are evolutionarily related and share a common receptor, the PTH/PTHLH receptor (PTH1R).