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  • • Hypoglycemic symptoms produced by fasting

    • Blood glucose below 50 mg/dL during symptomatic episodes

    • Relief of symptoms by IV administration of glucose

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Epidemiology

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  • • Insulinomas have been reported in all age groups

    • 75% are solitary and benign

    • 10% are malignant; metastases are usually evident at the time of diagnosis

    • Most are sporadic, solitary, benign lesions < 2 cm, occurring in equal distribution throughout the pancreas

    • 15% are manifestations of multifocal pancreatic disease—either adenomatosis, nesidioblastosis, or islet cell hyperplasia

    • In patients with multiple endocrine neoplasia 1 (MEN 1), insulinomas are typically multifocal

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Symptoms and Signs

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  • • Palpitations

    • Sweating

    • Tremulousness

    • Weight gain

    • Bizarre behavior

    • Memory lapse

    • Unconsciousness

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Laboratory Findings

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  • • Fasting hypoglycemia in the presence of inappropriately high levels of insulin

    • -Ratio of plasma insulin:glucose > 0.3 is diagnostic

    • Proinsulin levels > 40% suggest a malignant islet cell tumor

    • Elevated C-peptide levels exclude self-administration of insulin

    • Absent urine sulfonylurea levels exclude oral hypoglycemics

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Imaging Findings

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  • High-resolution CT and MRI scans demonstrate about 40% of tumors

    Endoscopic US exam of the pancreas successfully identifies 80-95% of tumors preoperatively

    Intraoperative US can identify a pancreatic tumor in nearly all cases and is the gold standard

    • More invasive techniques, such as transhepatic portal venous sampling and arteriography with selective calcium infusion are best used for reexploration after unsuccessful intraoperative localization

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  • • After diagnosis has been made by demonstration of fasting hypoglycemia and elevated insulin levels, the next step is localization of the insulinoma

    • Attempts at preoperative localization should be limited to noninvasive techniques (CT scan or MRI and endoscopic US)

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Rule Out

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  • • Non-islet cell tumors associated with hypoglycemia (hemangiopericytoma, fibrosarcoma, leiomyosarcoma, hepatoma, adrenocortical carcinoma)

    • Surreptitious self-administration of insulin

    • -Circulating C peptide levels are normal in these patients but elevated in most patients with insulinoma

    • Non-insulinoma pancreatogenous hypoglycemia syndrome

    • -Postprandial hypoglycemia with hyperinsulinism

      -Frequently post-gastric bypass procedure for morbid obesity

      -Calcium angiogram stimulates rise in hepatic vein insulin levels from all areas of the pancreas

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  • • Fasting determination of blood glucose and insulin levels; hypoglycemia with elevated insulin level

    • Preoperative localization

    • -CT scan or MRI

      -Endoscopic US

    • Control of hypoglycemia

    • Intraoperative US

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When to Admit

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  • • Severe, symptomatic hypoglycemia

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  • • The tumor may be enucleated if it is superficial, or resected as part of a partial pancreatectomy if it is deep-seated

    • Resection of metastatic lesions is warranted if technically feasible

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Surgery

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Indications

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  • • All patients with technically resectible lesions

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Medications

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  • • Diazoxide or octreotide to suppress insulin release

    • Streptozocin is the best chemotherapeutic agent

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Complications

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  • • Permanent cerebral damage

    • Obesity

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