No detectable (or minimal) parathyroid hormone-related protein (PTHrP) is normal.
Over the last 20-25 years, our understanding of PTH-rP has magnified along with our ability to discern the role PTH in multiple physiologic and pathologic conditions. PTH-rP production and action, along with the complex role it plays in cancer, is just beginning to be understood. PTH-rP is widely distributed in the human body and has broad roles in the endocrine, paracrine, and intracrine systems, which affect a multitude of physiologic and pathologic conditions, along with playing a central role in organogenesis. [1, 2]
PTH-rP resembles PTH in as much as they bind to the same type 1 PTH/PTHrP receptor and induce a similar response in the body. For this reason, hypercalcemia of malignancy resembles hyperparathyroidism and has been historically labeled a paraneoplastic syndrome. One of the many effects PTH-rP may have on the body is the induction of hypercalcemia; thus, hypercalcemia of malignancy might warrant an evaluation of PTH-rP levels.
Collection and Panels
See the list below:
Specimen - Blood
Container - Lavender (EDTA) or pink (K 2 EDTA); collect in chilled container
Collection method - Routine venipuncture
PTH-rP is not typically a part of a panel and should be ordered specifically.
PTH-related peptide is produced by some cancers, including those of the lung, breast, head, neck, bladder, gastrointestinal tract, and ovaries, as well as leukemia and lymphoma. High levels of PTH-related protein may be the cause of elevated calcium levels in many cancer patients. This condition is referred to humoral hypercalcemia of malignancy (HHM). Since PTHrP has the same N-terminal as PTH, it can bind to the same receptor and stimulate the action of PTH. This results in bone resorption and calcium resorption in the kidneys, but has minimal effect on calcium absorption in the intestines. Additionally, PTHrP has multiple proposed normal roles, including fetal calcium regulation during development, placental calcium transfer, lactation, dental eruption, smooth muscle relaxation, and epithelial cell growth. [3, 4, 5, 6, 7, 1]
PTHrP may be evaluated in patients with hypercalcemia associated with malignancy. It may also be monitored as a tumor marker during the treatment phase of disease. Current research is exploring applications of the administration of PTH-rP as treatment for several diseases, including breast cancer, diabetes, and osteoporosis.