Canis ISSN: 2398-2942

Pancreas: neoplasia: insulinoma

Synonym(s): Hyperinsulinism, insulin-secreting tumor, islet cell tumor

Contributor(s): David Bruyette, Andrew Gardiner, Laura Garrett

Introduction

  • Functional (ie insulin-producing) tumors of the endocrine pancreas affecting beta-islet cells. Malignant, with high metastatic potential spreading locally to lymph nodes and liver. Pulmonary metastasis unusual. Most cases have visible or invisible metastasis at time of diagnosis.
  • Cause: excessive secretion of insulin.
  • Signs: (hypoglycemia), episodic seizures, weakness, collapse, nervousness, tremors.
  • Diagnosis: signs, hypoglycemia and hyperinsulinemia.
  • Treatment: dextrose injections, anticonvulsant therapy (in acute phase), surgery, feeding change, medical management.
  • Prognosis: guarded long-term but controllable in the short term with good quality of life extending to many months if diagnosed early. Death (or euthanasia) eventually results due to metastatic disease and uncontrollable hypoglycemia.
    Print off the owner factsheet on Canine insulinoma to give to your client.

Pathogenesis

Etiology

  • Neoplastic beta-cells produce insulin (and other hormones) as a result of hypoglycemia Hypoglycemia , which normally inhibits insulin release.
  • Clinical signs due to low blood glucose ensue Blood biochemistry: glucose Serial blood glucose.
  • Hypoglycemia affects cerebral cells first as these cells have limited glycogen stores and poor potential for gluconeogenesis.
  • Sustained hypoglycemia leads to release of insulin antagonists (eg glucagon, growth hormone, catecholamines) to try and elevate blood glucose levels.
  • Insulin antagonists cause muscle tremor, nervousness, panting, hunger.

Pathophysiology

  • The major inhibitory stimulus for insulin secretion is hypoglycemia.
  • Insulinomas continue to release insulin despite hypoglycemia → continued tissue utilization of glucose → worsening hypoglycemia.
  • Hypoglycemia → reduced glucose available to the central nervous system (CNS) and later to peripheral nervous system and organs → seizures, lethargy, weakness, ataxia, bizarre behavior, coma.
  • Prolonged, severe hypoglycemia may → irreversible brain damage → rarely death.
  • Hypoglycemia → sympathetic nervous stimulation → behavior changes, shaking, nervousness, excitation.

Timecourse

  • 1 day-3 years.
  • Low blood glucose tolerated for prolonged periods without symptoms, further lowering of blood glucose produce symptomatic episodes.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Bell R, Mooney C T, Mansfield C S & Jones B R (2005) Treatment of insulinoma in a springer spaniel with streptozotocin. JSAP 46 (5), 247-250 PubMed.
  • Fischer J R et al (2000) Glucagon constant-rate infusion - a novel strategy for the management of hyperinsulinemic-hypoglycemic crisis in the dog. JAAHA 36 (1), 27-32 PubMed.
  • Shimada A et al (2000) Hypoglycemic brain lesions in a dog with insulinoma. J Comp Pathol 122, (1) 67-71 PubMed.
  • Tobin R L et al (1999) Outcome of surgical versus medical treatment of dogs with beta cell neoplasia - 39 cases (1990-1997). JAVMA 215 (2), 226-230 PubMed.
  • Trifonidou M A et al (1998) A retrospective evaluation of 51 dogs with insulinoma. Vet Q 20 (Suppl 1), S114-S115 PubMed.
  • Steiner J M & Bruyette D S (1996) Canine insulinoma. Comp Cont Ed Prac Vet 18 (1), 13-16 VetMedResource.
  • Dunn J K, Heath M F, Herrtage M E, Jackson K F & Walker M J (1993) Insulin secreting tumors of the canine pancreas; clinical and pathological features of 11 cases. JSAP 34 (7), 325-331 VetMedResource.
  • Dunn J K, Heath M F, Herrtage M E, Jackson K F & Walker M J (1992) Diagnosis of insulinoma in the dog; a study of 11 cases. JSAP 33 (11), 514-520 VetMedResource.
  • Caywood D D et al (1988) Pancreatic insulin-secreting neoplasms - clinical, diagnostic, and prognostic features in 73 dogs. JAAHA 24 (5), 577-584 VetMedResource.
  • Leifer C E et al (1986) Insulin-secreting tumor - diagnosis and medical and surgical management in 55 dogs. JAVMA 188 (1), 60-64 PubMed.

Other sources of information

  • Torrance A G (ed) et al (1998) Manual of SA Endocrinology. BSAVA publication.


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