proPTH

proPTH refers to the precursor form of parathyroid hormone (PTH), typically understood as the prohormone that gives rise to mature PTH. In humans, the PTH gene encodes a preprohormone that includes an N-terminal signal peptide, a prosegment (often described as proPTH), and the C-terminal PTH sequence. This arrangement directs the molecule through the secretory pathway and primes it for processing.

Biogenesis and processing occur in parathyroid chief cells and other neuroendocrine contexts. The signal peptide directs entry into the secretory pathway and is cleaved to form proPTH. ProPTH is then proteolytically processed by prohormone convertases to generate mature PTH, typically PTH (1-84). The mature hormone is stored in secretory granules and secreted in response to physiologic cues such as low blood calcium. Circulating PTH can include intact PTH (1-84) and various fragments; some truncated forms have distinct or reduced bioactivity.

Function and mechanism are mediated by the PTH1 receptor, primarily in bone and kidney. PTH raises serum calcium levels by promoting bone resorption, increasing renal calcium reabsorption, and stimulating production of active vitamin D, while influencing phosphate handling. The proPTH precursor itself is not biologically active; its role is to be processed into active PTH.

Clinical relevance centers on measuring parathyroid function, where intact PTH is routinely assessed. ProPTH serves as a conceptual precursor in discussions of PTH biosynthesis and regulation. Abnormal processing or secretion of PTH can contribute to disorders such as hyperparathyroidism or hypoparathyroidism, making understanding proPTH processing relevant to endocrine physiology.