Insulinoma: Description, Causes and Risk Factors:An insulinoma is a neuroendocrine tumor, deriving mainly from pancreatic islet cells, that secretes insulin. Some insulinomas also secrete other hormones, such as gastrin, 5-hydroxyindolic acid, adrenocorticotropic hormone (ACTH), glucagon, human chorionic gonadotropin, and somatostatin. The tumor may secrete insulin in short bursts, causing wide fluctuations in blood levels.About 90% of insulinomas are benign. Exact data for international incidence of insulinomas are not available. One source from Northern Ireland reported an annual incidence of 1 case per million persons.It is unclear why insulinomas occur in most cases, although some occur as part of a genetic condition called multiple endocrine neoplasia type 1. Normally, an insulinoma is a tumor of the pancreas that is derived from beta cells and secretes insulin. Beta cells secrete insulin in response to increases in blood glucose. The resulting increase in insulin acts to lower blood glucose back to normal levels at which point further secretion of insulin is stopped. In contrast, the secretion of insulin by insulinomas is not properly regulated by glucose and the tumors will continue to secrete insulin causing glucose levels to fall further than normal.Most patients with benign insulinomas can be cured with surgery. Persistent or recurrent hypoglycemia after surgery tends to occur in patients with multiple tumors. About two percent of patients may develop diabetes mellitus after their surgery.Symptoms:General Symptoms:Anxiety.
Patients with an insulinoma present with symptoms ofhypoglycemia secondary to excessive and uncontrolledsecretion of insulin. Symptoms are often nonspeci?c,episodic, vary among individuals and can differ from timeto time in the same individual. Hypoglycemic symptomscan be divided into two categories: neuroglycopenicand neurogenic symptoms. Neuroglycopenic symptomsare due to central nervous system (CNS) neuronal glucosedeprivation. They include behavioral changes, confusion,visual changes, fatigue, seizures and loss of consciousness. Ifhypoglycemia is severe and prolonged, death may result. Neurogenic symptoms are due to autonomic nervoussystem discharge caused by hypoglycemia. This resultsin cholinergic symptoms including hunger, sweating andparesthesia, and adrenergic symptoms including anxiety,tremor and palpitations. Cholinergic symptoms aremediated by acetylcholine released from sympatheticpostganglionic neurones. Noradrenaline release fromsympathetic postganglionic neurones, the adrenal medullaor both and adrenaline released from the adrenal medullamediate adrenergic symptoms.Diagnosis:The diagnosis is made by simultaneous measurements of blood sugar and insulin levels in the blood. A low blood sugar with a high insulin level confirms the diagnosis. Once the diagnosis made based on the biochemical analysis then the physician will perform further studies to detect the tumor in the pancreas.Tests:Blood C-peptide level.
Blood glucose level.
Blood insulin level.
Imaging: CT or MRI scan of the abdomen may be done to look for a tumor in the pancreas. If the test is negative, one of the following tests may be performed:Endoscopic ultrasound.
Pancreatic venous sampling for insulin.
Treatment:Surgery is the recommended treatment for insulinoma. The tumor is first found by tests or surgery. Medication may be used to get patients stable before surgery. If there is a single tumor it will be removed. However, if there are many tumors, part of the pancreas will need to be removed (partial pancreatectomy). At least 15% of the pancreas must be left to produce its enzymes. This may prevent the surgeon from removing the whole insulinoma tumor.If no tumor is found during surgery, or if you are not a candidate for surgery, you may get the drug diazoxide to lower insulin production and avoid hypoglycemia. A diuretic (water pill) is given with this medication to prevent the body from retaining fluid. Octreotide is used to reduce insulin release in some patients.Surgical Options:Enucleation: In this procedure the surgeon removes only the tumor preserving the rest of the pancreas. Since insulinomas usually occur on the surface of the pancreas and are covered by a capsule, they can be completely removed without having to remove any of the surrounding pancreas. The recurrence rate after enucleation of the insulinoma is very low and this is the treatment of choice if it is technically possible to perform this operation.
Pancreatic resection (removal): Less commonly the surgeon may remove part of the pancreas where the tumor is located by utilizing operative procedures such as a distal pancreatectomy or a Whipple operation. These operations are performed as an exception rather than commonly since the vast majority of the tumors can be removed with enucleation.
Laparoscopic operations: With laparoscopic surgery the post-operative recovery period and amount of pain is reduced, hospital stay is shorter and patients are able to return to their normal activity much faster.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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