Differential Diagnosis for Hypoglycaemia with Normal C-Peptide Level
Single Most Likely Diagnosis
- Exogenous Insulin Administration: This is the most likely diagnosis because the presence of hypoglycemia with a normal C-peptide level suggests that the hypoglycemia is not due to endogenous insulin overproduction. Exogenous insulin administration, whether intentional (as in insulin therapy for diabetes) or unintentional (as in factitious hypoglycemia), would suppress endogenous insulin production, leading to low or normal C-peptide levels despite hypoglycemia.
Other Likely Diagnoses
- Oral Hypoglycemic Agents: Certain oral hypoglycemic agents, especially sulfonylureas and meglitinides, can stimulate insulin release from the pancreas. However, in cases where these agents cause hypoglycemia, the C-peptide level might be elevated due to the stimulated insulin release. Yet, in some instances, especially with prolonged use or in sensitive individuals, the C-peptide level might not be significantly elevated, making this a possible consideration.
- Hypoglycemia Due to Other Medications: Various medications, such as beta-blockers, salicylates, and pentamidine, can cause hypoglycemia through different mechanisms. The C-peptide level in these cases would typically be low or normal because the hypoglycemia is not due to endogenous insulin overproduction.
Do Not Miss Diagnoses
- Insulinoma with Insulin Antibodies: Although less common, it's crucial not to miss an insulinoma, especially if there are autoantibodies to insulin that could interfere with insulin assays, potentially leading to a normal or low measured C-peptide level despite elevated insulin levels.
- Hepatic or Renal Failure: Both hepatic and renal failures can lead to hypoglycemia through different mechanisms, including impaired glucose production and decreased clearance of insulin, respectively. The C-peptide level might be normal or low in these conditions, depending on the severity of the organ dysfunction and the presence of other complicating factors.
Rare Diagnoses
- Non-Islet Cell Tumor Hypoglycemia (NICTH): This condition is characterized by the production of insulin-like growth factor II (IGF-II) or its precursors by non-islet cell tumors, leading to hypoglycemia. The C-peptide level is typically low or normal because the hypoglycemia is not caused by endogenous insulin overproduction.
- Autoimmune Hypoglycemia: This is a rare condition where autoantibodies to insulin or the insulin receptor cause hypoglycemia. The C-peptide level might be normal or low, depending on the specific mechanism and the presence of insulin resistance or other metabolic disturbances.