Chromogranin A

Function

Chromogranin A (CgA) is a protein found inside neuroendocrine cells. These specialized cells receive messages from the nervous system and respond by releasing hormones into the blood. CgA is stored in the secretory granules of these cells and is co-released with various hormones. Because most neuroendocrine tumors (NETs) secrete CgA, it serves as a sensitive, albeit non-specific, circulating tumor marker.

Why it is Ordered

This test is primarily used in the management of Neuroendocrine Tumors (NETs). It is ordered for:

• Diagnosis: Helping identify tumors like carcinoid tumors, pheochromocytomas, or neuroblastomas.
• Monitoring: Assessing the effectiveness of treatment (surgery or chemotherapy).
• Surveillance: Detecting early recurrence in patients previously treated for NETs.

Associated Conditions

Elevated CgA levels are associated with several clinical states:

• Carcinoid Tumors: Often found in the GI tract or lungs.
• Pancreatic Islet Cell Tumors: Such as insulinomas or gastrinomas.
• Pheochromocytoma: A tumor of the adrenal glands.
• Non-Neoplastic Conditions: Chronic atrophic gastritis, liver disease, and renal failure can also cause elevations.