PTHrPsezernierung

PTHrPsezernierung refers to the secretion of parathyroid hormone-related protein (PTHrP), a secreted protein encoded by the PTHLH gene in humans. PTHrP is produced in many tissues and acts largely through paracrine and autocrine signaling, though some circulating PTHrP can contribute to systemic effects in certain conditions. The protein shares structural similarity with parathyroid hormone (PTH) in its N-terminal region, allowing it to activate the PTH1 receptor (PTH1R) and stimulate cAMP signaling, while many biological actions of PTHrP are independent of PTH1R in other contexts.

Secretion of PTHrP involves synthesis as a preproprotein, routing into the secretory pathway, and proteolytic processing into multiple peptide forms of varying lengths. In several cell types, the N-terminal peptide is considered the biologically active portion. PTHrP secretion is typically autocrine or paracrine; some tissues release PTHrP in response to calcium levels, mechanical cues, or developmental signals. Regulation of PTHLH gene expression is complex and tissue-dependent, with influences from factors such as retinoic acid, vitamin D, TGF-β, and estrogens.

Physiological roles include regulation of endochondral bone development and placental calcium transport during fetal growth. In adults, PTHrP participates in mammary gland development, cartilage homeostasis, and smooth muscle function, among other roles.

Clinical relevance centers on the hypercalcemia of malignancy: tumors that secrete PTHrP can cause humoral hypercalcemia of malignancy (HHM). Serum PTHrP measurement supports HHM diagnosis and management, which focuses on treating the underlying tumor, hydration, and antiresorptive therapies.