Chromogranin A (CgA) Test – Purpose, Normal Range, High & Low Level Causes

Overview

The Chromogranin A (CgA) Test is a specialized blood test that measures the level of chromogranin A, a protein released by neuroendocrine cells. These cells are found in many organs and are responsible for releasing hormones in response to signals from the nervous system.

The test is mainly used as a tumor marker to help detect and monitor neuroendocrine tumors (NETs) — cancers that develop from hormone-producing cells. Examples include carcinoid tumors, pheochromocytoma, neuroblastoma, and pancreatic islet cell tumors.

However, elevated CgA levels may also be seen in non-cancerous conditions such as chronic illnesses, kidney disease, or long-term use of proton pump inhibitors (PPIs) (used for acidity).

What is Chromogranin A?

Chromogranin A is a protein that is stored and released by neuroendocrine cells. It serves as a precursor molecule, which means it can be broken down into smaller peptides that regulate various processes in the nervous and endocrine systems.

Because neuroendocrine tumors often produce excess amounts of chromogranin A, the CgA blood test becomes an important diagnostic and monitoring tool for these conditions.

Where is Chromogranin A Produced in the Body?

Chromogranin A is not produced everywhere — it is released by specialized cells known as neuroendocrine cells, which are scattered throughout the body.

Main sites of production include:

• Adrenal medulla (inner part of adrenal glands)
• Pancreatic islet cells (hormone-producing cells of the pancreas)
• Gastrointestinal tract (especially the stomach and intestines)
• Thyroid gland (C-cells)
• Other hormone-secreting tissues in the nervous and endocrine systems

These cells release chromogranin A when hormones like adrenaline or serotonin are secreted, making it an indirect indicator of neuroendocrine activity.

Functions and Importance of Chromogranin A

Chromogranin A plays multiple roles in the body’s neuroendocrine functions.

1. Precursor Protein

It acts as a precursor molecule, which means it breaks down into smaller functional peptides. These smaller peptides help regulate:

• Hormone secretion
• Blood vessel function
• Communication between nerves and hormones

2. Role in Hormone Storage and Release

Chromogranin A helps in the storage and release of catecholamines — the group of hormones that includes adrenaline and noradrenaline, which control stress response and blood pressure.

3. Biomarker in Medicine

In clinical practice, CgA is widely used as a biomarker to:

• Detect neuroendocrine tumors
• Monitor treatment response (if levels decrease, it means treatment is working)
• Detect tumor recurrence during follow-up

However, doctors always confirm elevated CgA levels with imaging studies or biopsy, since other non-cancerous conditions can also raise it.

Causes of Low Chromogranin A Levels

Low or negative chromogranin A levels are usually not a cause for concern.

Possible causes include:

• Minimal or no neuroendocrine activity in the body
• Natural variation in healthy individuals

In short, low levels of chromogranin A rarely indicate any disease.

Symptoms of Low Levels

• Usually, no specific symptoms are linked to low CgA.
• It is not used to diagnose deficiency or any medical condition.

Causes of High Chromogranin A Levels

High levels of chromogranin A may be due to several conditions — some serious (like tumors) and some benign (like medication effects).

Common causes include:

1. Neuroendocrine tumors (NETs):
   • Carcinoid tumors
   • Pheochromocytoma
   • Pancreatic islet cell tumor
   • Medullary thyroid carcinoma
   • Neuroblastoma
2. Chronic kidney disease (CKD):
   • The kidneys help remove chromogranin A; poor function leads to accumulation.
3. Chronic atrophic gastritis:
   • Inflammation of the stomach lining can increase CgA levels.
4. Prolonged use of PPIs (Proton Pump Inhibitors):
   • Drugs like omeprazole, pantoprazole, or esomeprazole increase gastrin and CgA levels artificially.
5. Liver cirrhosis or inflammation:
   • Liver diseases slow down the breakdown and clearance of CgA.

Symptoms of High Chromogranin A Levels

Symptoms depend on the underlying cause, especially if the reason is a neuroendocrine tumor.

Common symptoms include:

• Flushing, diarrhea, and wheezing (seen in carcinoid syndrome)
• Palpitations, high blood pressure, sweating (seen in pheochromocytoma)
• Abdominal pain, unexplained weight loss, or visible mass
• Fatigue and weakness
• Digestive symptoms like nausea or loss of appetite

These symptoms occur due to excessive hormone secretion from tumor cells.

Reference Range

It’s important to note that CgA is not tumor-specific, so an elevated level alone doesn’t confirm cancer — further testing (CT, MRI, PET scan, biopsy) is required.

Sample Type and Test Procedure

• Sample Required: Blood (serum or plasma)
• Collection Method: A simple venous blood draw from the arm
• Special Requirement:
  • PPI medicines (like omeprazole) should ideally be stopped 5–14 days before testing (as advised by the doctor).
  • Blood is collected in a clean, additive-free tube.
  • Avoid stress or heavy meals before the test for accurate results.

Test Preparation

• Medication: Inform your doctor about all medications, especially PPIs or H2 blockers.
• Fasting: Usually, fasting for 8–10 hours is preferred.
• Avoid alcohol and caffeine 24 hours before testing.
• Medical conditions: Tell your doctor if you have kidney disease or liver issues, as they can affect results.
• Sample timing: Morning sample preferred for consistency.

When to Consult a Doctor

You should consult a doctor if:

• You have unexplained flushing, diarrhea, or palpitations.
• You are undergoing treatment for a neuroendocrine tumor and need progress monitoring.
• You are on PPI therapy for long duration and have persistent digestive symptoms.
• You have high CgA levels on test reports — your doctor will guide further tests like imaging or biopsy.

Early diagnosis and proper monitoring are essential in detecting neuroendocrine tumors before they spread.

Important Word Explanations

• Neuroendocrine Cells: Specialized cells that release hormones in response to nerve signals.
• Tumor Marker: A substance in the blood that helps detect or monitor cancer.
• Catecholamines: Hormones like adrenaline and noradrenaline that control stress response.
• PPI (Proton Pump Inhibitor): Medicine that reduces stomach acid (e.g., omeprazole, pantoprazole).
• Carcinoid Syndrome: A set of symptoms caused by hormone-secreting tumors, including flushing and diarrhea.

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