1. Why Evaluate the Pancreas’s Insulin Secretion Capacity?
When planning treatment for a person with diabetes, knowing how much ability their pancreas has left to produce its own insulin is crucial. This is key information for differentiating between Type 1 and Type 2 diabetes, or for determining when a patient with Type 2 diabetes needs to start insulin therapy.
2. The Principle of the Glucagon Stimulation Test (GST)
– Role of Glucagon: While glucagon is generally known as a hormone that raises blood sugar, it also has the role of directly and powerfully stimulating the insulin-producing cells of the pancreas (beta cells) to secrete insulin.
– Test Procedure: The test involves giving the patient an injection of glucagon and then measuring how much the C-peptide level (insulin’s ‘twin’ substance) increases in a blood sample taken after a set time (e.g., 6 minutes).
– Interpreting the Results: If the pancreatic beta cells are still highly functional, they will respond strongly to the glucagon stimulation, and the C-peptide level will increase significantly. Conversely, if the beta cells are mostly destroyed, as in Type 1 diabetes, stimulating with glucagon will result in almost no C-peptide secretion.
3. The Significance of the Test
This is a dynamic test that evaluates the pancreas’s potential for insulin secretion, its ‘insulin secretory reserve,’ by stimulating it to its ‘maximum’ capacity. It can assess the true capability of the pancreas more accurately than simply looking at a fasting C-peptide level. The results are used as important evidence for accurately diagnosing the patient’s type of diabetes and for determining the future course of treatment.
Summary: The ‘glucagon stimulation test’ is a precise test that evaluates how much insulin-producing capacity a patient’s own pancreas has left by maximally stimulating the pancreas with glucagon and measuring the resulting amount of C-peptide.
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