Insulinoma Clinical Presentation

Updated: Oct 03, 2017
  • Author: Zonera Ashraf Ali, MBBS; Chief Editor: Neetu Radhakrishnan, MD  more...
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Presentation

History and Physical Examination

Features of the history in patients with insulinoma are as follows:

  • About 85% of patients present with symptoms of hypoglycemia that include diplopia, blurred vision, palpitations, or weakness.
  • Other symptoms include confusion, abnormal behavior, unconsciousness, or amnesia.
  • About 12% of patients have grand mal seizures.
  • Adrenergic symptoms (hypoglycemia causes adrenalin release) include weakness, sweating, tachycardia, palpitations, and hunger.
  • Symptoms may be present from 1 week to as long as several decades prior to the diagnosis (1 mo to 30 y, median 24 mo, as found in a large series of 59 patients). [16] Symptoms may occur most frequently at night or in the early morning hours.
  • Hypoglycemia usually occurs several hours after a meal.
  • In severe cases, symptoms may develop in the postprandial period. Symptoms can be aggravated by exercise, alcohol, hypocaloric diet, and treatment with sulfonylureas.
  • Weight gain occurs in 20-40% of cases, because patients may eat frequently to avoid symptoms.
  • Case reports describe patients with type 2 diabetes who develop hypoglycemia from insulinoma [17, 18]
  • Symptoms caused by effects of local tumor mass are very rare in insulinoma.

Most patients with insulinoma have normal physical examination findings.

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Causes

The genetic changes in neuroendocrine tumors are under investigation. [19] The gene of multiple endocrine neoplasia type 1, an autosomal dominant disease, is called MEN1 and maps to band 11q13. MEN1 is thought to function as a tumor suppressor gene. Data suggest that the MEN1 gene also is involved in the pathogenesis of at least one third of sporadic neuroendocrine tumors. Researchers were able to detect loss of heterozygosity in band 11q13 in DNA samples from resected insulinoma tissue by using fluorescent microsatellite analysis.

In a study of 12 children with insulinoma, four cases showed heterozygous mutations of MEN1 on 11q. Aneuploidy of chromosome 11 and other chromosomes was common in both MEN1 and non-MEN1 insulinomas. [20]

One study showed k-ras mutation to be present in 23% of insulinomas.

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