Parathyroid hormone (PTH) is a hormone secreted by the parathyroid glands and involved in bone remodeling. PTH activates osteoclasts within bone marrow to release calcium from bone to increase calcium levels in the blood. PTH is a vital hormone for overall health. PTH is secreted as an 84 amino acid hormone, but only amino acids 1-34 are required for receptor interactions. A variety of diseases are associated with PTH dysregulation, including parathyroidism (hyper / hypo) and calceaemia (hyper / hypo).