## Clinical Context The patient presents with recurrent hypoglycemic episodes temporally related to atenolol initiation. Non-selective beta-blockers (and to a lesser extent, beta-1 selective agents like atenolol) impair hypoglycemic awareness and mask sympathomimetic warning signs (tremor, palpitations, sweating) by blocking beta-2 adrenergic receptors in the pancreas and sympathetic nervous system. ## Why Continuous Glucose Monitoring with Symptom Diary Is the Best Investigation **Key Point:** CGM provides real-time glucose trends and captures asymptomatic hypoglycemic episodes, while the symptom diary correlates glucose nadir with absence of typical warning symptoms—the hallmark of beta-blocker–induced hypoglycemic unawareness. **High-Yield:** Beta-blockers cause hypoglycemic unawareness by: 1. Blocking pancreatic beta-2 receptors → reduced glucagon secretion 2. Blocking sympathetic alpha-2 and beta-2 receptors → impaired epinephrine and norepinephrine release 3. Masking adrenergic warning signs (tremor, palpitations, anxiety) **Clinical Pearl:** Patients on beta-blockers may experience severe hypoglycemia without the usual prodromal symptoms, making them prone to seizures or loss of consciousness. CGM + symptom diary is the gold standard to document this dissociation. ## Why Other Investigations Are Not Optimal | Investigation | Rationale for Not Being First-Line | |---|---| | Fasting blood glucose & HbA1c | Assess glycemic control but do NOT capture the specific phenomenon of hypoglycemic unawareness or asymptomatic hypoglycemic episodes | | Serum C-peptide | Evaluates endogenous insulin secretion; not relevant to the mechanism of beta-blocker–induced hypoglycemic unawareness | | Insulin antibody assay | Screens for autoimmune insulin resistance; unrelated to beta-blocker adverse effects | **Mnemonic:** **CGM-AWARE** — Continuous Glucose Monitoring documents Asymptomatic Recurrent Episodes in beta-blocker users.
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