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Insulinoma : Clinical Features

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Clinical Features of Insulinoma: Uncontrolled insulin secretion leads to severe hypoglycemia which causes autonomic and neuroglycopenic symptoms. The symptoms are triggered by fasting and exercise and relieved by glucose administration. The patients learn to avoid symptoms by frequent eating and obesity may result.

Neuroglycopenic symptoms: Glucose is the main source of energy for brain. Severe hypoglycemia causes neuroglycopenia. The manifestations include severe weakness, confusion, agitation, delayed reactions, blurred vision, seizures, transient loss of consciousness, and hypoglycemic coma. The neuroglycopenic symptoms may be present for several years before the diagnosis of insulinoma.

Autonomic symptoms: Catecholamine release causes palpitations and tremor. Cholinergic manifestations include sweating, hunger, and paraesthesia.

Whipple Triad:The triad of hypoglycemic symptoms, fasting plasma glucose levels <50 mg/dl, and symptom relief after glucose administration is known as Whipple triad. It is not specific for insulinoma. The useful laboratory findings include fasting plasma glucose levels <50 mg/dl, and elevated levels of serum insulin, C-peptide, and proinsulin. A plasma insulin-to-glucose ratio over 0.3 is considered positive for insulinoma.

Case history: The patient was a 42 y/o male with a 6-month history of multiple attacks of dizziness, confusion and fainting which used to be relieved by eating food. His general and systemic examination was non-contributory. Fasting blood sugar done twice was 51 and 49 mg/dL. His fasting serum Insulin level was elevated at 26.8 mIU/L (Ref. range 2-25 mIU/L). Serum C-peptide level was also elevated at 6.06 ng/mL (Ref. range 0.81 -3.5 ng/mL).

Abdominal computed tomography (CT) scan with contrast revealed a well-defined hypervascular lesion involving uncinate process of pancreas measuring 15 mm in diameter. MRI studies did not reveal any lesions in pituitary, thyroid or liver.

A distal pancreactectomy was performed and tumor located in the uncinate process of pancreas was removed. The photograph shows resected pancreatic portion with a well-circumscribed round to oval tumor measuring 1.2 cm in diameter. The microscopic examination showed insulinoma with cells arranged in gyriform and trabecular patterns.

Case courtesy of: Dr. Sanjay D. Deshmukh (Professor of Pathology) & Dr. J. M. Gadekar (Head of Surgery Dept.), Dr. Vithalrao Vikhe Patil Medical College & Hospitals, Ahmednagar, India.

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