Somatostatinomas are a

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

of the delta cells of the endocrine pancreas that produces

somatostatin Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by #Nomenclature, several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G ...

. Increased levels of somatostatin inhibit pancreatic hormones and gastrointestinal hormones. Thus, somatostatinomas are associated with mild

diabetes mellitus Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained hyperglycemia, high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or th ...

(due to inhibition of

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...

release), steatorrhoea and

gallstones A gallstone is a stone formed within the gallbladder from precipitated bile components. The term cholelithiasis may refer to the presence of gallstones or to any disease caused by gallstones, and choledocholithiasis refers to the presence of ...

(due to inhibition of cholecystokinin release), and

achlorhydria Achlorhydria and hypochlorhydria are states where the production of hydrochloric acid in gastric secretions of the stomach is absent or low, respectively. Achlorhydria is commonly a complication of some other disease, such as chronic '' Helicobac ...

(due to inhibition of

gastrin Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility. It is released by G cells in the pyloric antrum of the stomach, duodenum, and the pancreas. ...

release). Somatostatinomas are commonly found in the

head of pancreas The pancreas (plural pancreases, or pancreata) is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrin ...

. Only ten percent of somatostatinomas are functional tumours, and 60–70% of tumours are malignant. Nearly two-thirds of patients with malignant somatostatinomas will present with metastatic disease.

Pathophysiology

In a normal subject, actions of

include: :*In the

anterior pituitary gland The anterior pituitary (also called the adenohypophysis or pars anterior) is a major organ of the endocrine system. The anterior pituitary is the glandular, anterior lobe that together with the posterior pituitary (or neurohypophysis) makes up ...

, the effects of somatostatin are: ::* Inhibit the release of

growth hormone Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in ...

, thus opposing the effects of growth hormone-releasing hormone (GHRH) ::* Inhibit the release of thyroid-stimulating hormone (TSH) :*Somatostatin suppresses the release of gastrointestinal hormones ::*

Gastrin Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility. It is released by G cells in the pyloric antrum of the stomach, duodenum, and the pancreas. ...

::* Cholecystokinin (CCK) ::* Secretin ::* Motilin ::*

Vasoactive intestinal peptide Vasoactive intestinal peptide, also known as vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is a peptide of 28 amino acid residue (chemistry), residues that belongs to a Secretin family, glu ...

(VIP) ::* Gastric inhibitory polypeptide (GIP) ::* Enteroglucagon :* Lowers the rate of gastric emptying, and reduces smooth muscle contractions and blood flow within the intestine :* Suppresses the release of pancreatic hormones ::* Inhibits the release of

::* Inhibits the release of

glucagon Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises the concentration of glucose and fatty acids in the bloodstream and is considered to be the main catabolic hormone of the body. It is also used as a Glucagon (medic ...

:* Suppresses the exocrine secretory action of

pancreas The pancreas (plural pancreases, or pancreata) is an Organ (anatomy), organ of the Digestion, digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a ...

. This explains how abnormally elevated

can cause

, by inhibiting

secretion, steatorrhoea by inhibiting cholecystokinin and secretin, gall stones by inhibiting cholecystokinin which normally induce

gallbladder In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow Organ (anatomy), organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath t ...

myocytes to contract, and hypochlorhydria caused by inhibiting

, which normally stimulate acid secretion. Somatostatinomas are associated with calcium deposits called psammoma bodies.

Diagnosis

Fasting plasma somatostatin greater than 30 pg/mL. SRS (Somatostatin Receptor Scintigraphy) – It is a radio-nucleotide scan by giving Octreotide tagged with , which shows an increase in uptake by the tumour cells.

Treatment

Treatment is by

chemotherapy Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...

with streptozocin, dacarbazine, doxorubicin or by 'watchful waiting' and surgical debulking via Whipple procedure and other resections of the gastrointestinal organs affected.

References

:6. Soga J, Yakuwa Y. Somatostatinoma/inhibitory syndrome: a statistical evaluation of 173 reported cases as compared to other pancreatic endocrinomas. J Exp Clin Cancer Res, 1999; 18:13–22. MID: 10374671

External links

{{Endocrine gland neoplasia Endocrine neoplasia Rare cancers