What is Chromogranin?
Chromogranin, most often analyzed as chromogranin A (CgA), is a protein that is stored and released from neuroendocrine cells. These cells are found throughout the body, including in the gastrointestinal tract, pancreas, adrenal glands, and nervous system. Chromogranin functions as a so-called secretory granule marker and is used clinically as a biomarker to identify and monitor certain neuroendocrine tumors (NETs). Chromogranin A is secreted together with hormones and neurotransmitters from neuroendocrine cells, and elevated levels in the blood may therefore reflect increased activity or presence of neuroendocrine tissue.
Why is Chromogranin analyzed?
Chromogranin analysis is used in the investigation, diagnosis, and follow-up of neuroendocrine tumors, such as carcinoids, insulinomas, gastrinomas, and pheochromocytomas. The result can also be used to monitor disease activity and treatment response in patients with known neuroendocrine disease. Chromogranin is not a cancer-specific test, but should always be interpreted in conjunction with clinical symptoms, imaging and other laboratory tests. Elevated levels can also occur in conditions other than cancer.
What can high levels of Chromogranin indicate?
Elevated levels of Chromogranin may indicate increased activity in neuroendocrine cells. Common causes of elevated chromogranin include:
- Neuroendocrine tumors (NETs)
- Carcinoid tumors
- Pheochromocytoma
- Gastrinoma and Zollinger–Ellison syndrome
- Chronic renal failure
- Long-term treatment with proton pump inhibitors (PPIs)
Treatment with proton pump inhibitors (e.g. omeprazole, esomeprazole) is a common cause of falsely elevated chromogranin values, as these drugs increase gastrin release and thereby stimulate chromogranin production.
What can low levels of chromogranin indicate?
Low or normal levels of chromogranin usually indicate that there is no increased neuroendocrine activity. However, a normal value does not completely rule out neuroendocrine disease, especially in early stages or in small tumors with low hormonal activity.
Factors that can affect the Chromogranin value
Several factors can affect the level of chromogranin in the blood and should be considered when interpreting:
- Use of proton pump inhibitors (PPIs)
- Impaired renal function
- Stress and acute illness
- Inflammatory conditions
- Old age
To improve the reliability of the analysis, it is often recommended that proton pump inhibitors be discontinued 1–2 weeks before sampling, if medically possible.
Interpretation and clinical use
Chromogranin is a useful biomarker in cases of suspected neuroendocrine disease, but is not intended as a stand-alone screening test in asymptomatic individuals. The result should always be interpreted by medical expertise in relation to symptoms, medical history, medication use and other diagnostic findings. In the event of deviating values, additional investigation with imaging diagnostics, hormone tests or follow-up laboratory tests may be necessary to establish the diagnosis and treatment strategy.
Reference interval S-Chromogranin
In order to assess whether a test result is normal or abnormal, the value of S-Chromogranin is compared to established reference intervals. The interpretation of the result is not based solely on the number itself, but should always be put in relation to individual factors such as symptoms, medication use and other clinical findings.
≤ 2.0 nmol/L
Conversion: 1 ng/mL corresponds to approximately 0.0204 nmol/L.
Interpretation of test results
Elevated levels of chromogranin may be consistent with increased neuroendocrine activity and occur in several types of neuroendocrine tumors, such as pheochromocytoma, carcinoid tumors, and neuroblastoma. Elevated values can also be seen in small cell lung cancer. It is important to know that chromogranin is not a tumor-specific marker. Elevated levels can also be caused by other factors, such as impaired kidney function or treatment with proton pump inhibitors (PPIs). Test results should therefore always be interpreted by medical expertise in relation to symptoms, drug use, and other clinical findings.