Chromogranin A (CgA) or parathyroid secretory protein 1 (gene name CHGA) is a member of the chromogranin/secretogranin (granins) family of neuroendocrine secretory proteins, i.e. it is located in secretory vesicles of neurons and endocrine cells. Examples of cells producing chromogranin A are chromaffin cells of the adrenal medulla, enterochromaffinlike cells and beta cells of the pancreas. 

Chromogranin A is the precursor to several functional peptides including vasostatin, pancreastatin, catestatin and parastatin. These peptides negatively modulate the neuroendocrine function of the releasing cell (autocrine) or nearby cells (paracrine). Other peptides derived from chromogranin A with uncertain function include chromostatin, WE-14 and GE-25. Neuroendocrine tumors (NETs), which originate from neuroendocrine cells, are found widely distributed throughout the body.

The most common sites of NET are the lung, stomach, appendix, cecum, duodenum, pancreas, jejunum/ileum, colon and rectum. NET arising from the gastrointestinal tract are collectively known as gastroenteropancreatic neuroendocrine tumors (GEP-NET) and account for approximately 2/3 of incident NET. The annual incidence of NET is estimated as 2 –5 cases per 100000 population. Therefore, CgA has become the most important circulating tumour marker for different kinds of neuroendocrine tumours. 

Levels are increased in carcinoid tumours, neuroblastoma, pheo-chromocytoma, and gastroenteropancreatic tumours such as gastrinoma, glucagonoma, insulinoma. An increase of CgA levels in patients with prostate carcinoma is a hint for an unfavourable outcome of the disease. The determination of Chromogranin A helps in the detection of neuroendocrine tumors and is used to assess the course of cancer treatment. And Chromogranin A levels show an excellent correlation to the tumour mass and are therefore widely used to monitor the outcome of therapies.

LDN has developed an ELISA that determines highly specific and without high-dose-hook-effect CgA in serum and which has been validated according to the requirements of the new IVDR.