endocrine and metabolic disorders
Hypoglycemia
Diagnosis of Hypoglycemia
Measurement of blood glucose level In patients with diabetes who are takinginsulinor antihyperglycemic medications, a blood glucose level < 70 mg/dL (3.8 mmol/L) correlated with clinical findings is consistent with hypoglycemia. The severity of hypoglycemia in patients with diabetes is based on blood glucose levels and need for assistance Level 1 (mild) hypoglycemia: blood glucose<70 mg/dL (<3.8 mmol/L) but≥54 mg/dL (≥3 mmol/L) Level 2 (moderate) hypoglycemia: blood glucose<54 mg/dL (<3 mmol/L) Level 3 (severe) hypoglycemia: hypoglycemia requiring assistance from another person due to change in mental or physical status In patients not receiving diabetes treatment, diagnosis of a hypoglycemic disorder requires confirmation of Whipple's triad or confirmation of low blood glucose during a fast. Whipple's triad includes Symptoms of hypoglycemia Low plasma glucose level (< 55 mg/dL [3.05 mmol/L]) that occurs at the time symptoms occur Decrease in symptoms whendextroseor other sugar is given If a clinician is present when symptoms occur, blood should be sent for glucose testing in a tube containing a glycolytic inhibitor. If glucose is normal, hypoglycemia is ruled out and other causes of symptoms should be considered. If glucose is abnormally low, and no cause can be identified from history (eg, medications, adrenal insufficiency, severe undernutrition, organ failure ,sepsis), seruminsulin,insulinantibodies, and sulfonylurea levels should be checked. C-peptide and proinsulin measured from the same tube can distinguishinsulin-mediated from non–insulin-mediated and factitious from physiologic hypoglycemia and can obviate the need for further testing. In practice, however, it is unusual that clinicians are present when patients experience symptoms suggestive of hypoglycemia. Home glucose meters are unreliable for quantifying hypoglycemia, and there are no clear glycosylated hemoglobin (HbA1C) thresholds that distinguish long-term hypoglycemia from normoglycemia. Continuous glucose monitors are also less accurate in the hypoglycemic range. So the need for more extensive diagnostic testing is based on the probability that an underlying disorder that could cause hypoglycemia exists given a patient’s clinical appearance and coexisting illnesses. To differentiate betweeninsulin-mediated and non-insulin–mediated hypoglycemia and to determine the etiology of hypoglycemia, a 48- or 72-hour fast may be required. A prolonged fast can trigger hypoglycemia in a person who has a history of fasting hypoglycemia. A 72-hour fast done in a controlled setting is the standard for diagnosis. However, in almost all patients with a hypoglycemic disorder, a 48-hour fast is adequate to detect hypoglycemia, and a full 72-hour fast may not be necessary. Patients drink only noncaloric, noncaffeinated beverages. Plasma glucose is measured at baseline, whenever symptoms occur, and every 4 to 6 hours or every 1 to 2 hours if glucose falls below 70 mg/dL (3.8 mmol/L). Seruminsulin, C-peptide, and proinsulin should be measured when a simultaneous plasma glucose measurement is<55 mg/dL (<3.05 mmol/L). These measurements help to distinguish endogenous from exogenous (factitious) hypoglycemia. The fast is terminated at 72 hours if the patient has experienced no symptoms and glucose remains normal, sooner if glucose decreases to≤45 mg/dL (≤2.5 mmol/L) in the presence of symptoms of hypoglycemia. End-of-fast measurements include beta-hydroxybutyrate (which should be low if the cause is an insulinoma), serum sulfonylurea to detect medication-induced hypoglycemia, and plasma glucose after IVglucagoninjection to detect an increase characteristic of insulinoma. Sensitivity, specificity, and predictive values for detecting hypoglycemia by this protocol have not been reported. If symptomatic hypoglycemia has not occurred by 48 to 72 hours, the patient should exercise vigorously for about 30 minutes. If hypoglycemia still does not occur, insulinoma is essentially excluded and further testing is generally not indicated. There is no definitive lower limit of glucose that unequivocally defines pathologic hypoglycemia during a monitored fast. Females tend to have lower fasting glucose levels than males and may have glucose levels as low as 50 mg/dL (2.8 mmol/L) without symptoms. In patients with a history of a postprandial pattern of hypoglycemia, such as in a patient with hypoglycemia after Metabolic and Bariatric Surgery , a prolonged fast may not trigger hypoglycemia. In those individuals, hypoglycemia should be assessed after a mixed meal or after eating a meal that is similar to a meal that previously triggered hypoglycemic symptoms (often high in refined carbohydrates and fat). Fingerstick glucose measurements and blood tests for glucose, 