Somatostatinoma

　　Somatostatinomas are one of the rarest functional endocrine tumors. The etiology is still under study. The secretion of large amounts of somatostatin is the fundamental cause of the disease. Somatostatin has a wide range of biological effects: ① Inhibits smooth muscle contraction: stomach, intestines, biliary tract; ② Inhibits secretion: stomach (including gastric acid), pancreas (endocrine and exocrine), liver (bile), small intestine; ③ Inhibits the absorption of water, electrolytes, and nutrients (glucose, amino acids, triglycerides) in the small intestine; ④ Excites or inhibits enteric neurons; ⑤ Inhibits the proliferation of mucosal cells; ⑥ Reduces blood flow to the gastrointestinal tract; ⑦ Inhibits the secretion of gastrointestinal hormones: gastrin, CCK, insulin, glucagon, enterogastrone, secretin, motilin, GIP, VIP, PP, NT; ⑧ Inhibits the secretion of other hormones: growth hormone, thyroid-stimulating hormone, renin; ⑨ Other inhibitions: release of acetylcholine in the enteric plexus, platelet aggregation, etc. In pathological conditions, the large release of somatostatin produces the clinical symptoms of somatostatinomas.

　　Due to the release of large amounts of somatostatin by somatostatinomas, it causes a comprehensive syndrome including steatorrhea, diabetes, hypochlorhydria, and cholelithiasis. Somatostatin can inhibit the release of polypeptide hormones, which can cause widespread pathological and physiological changes in the body, mainly including the following aspects:

　　1. Central nervous system

　　Inhibits the release of trophic hormones by the pituitary, such as growth hormone, thyrotropin, adrenocorticotropic hormone, and prolactin, etc.

　　2, Gastrointestinal system

　　Gastrointestinal somatostatin can directly inhibit the secretion of gastric acid, gastric emptying, duodenal motility, bile duct and gallbladder motility, exocrine function of the pancreas, and absorption of glucose, amino acids, and triglycerides, etc. Somatostatin has paracrine effects locally in the gastrointestinal tract and plays a negative feedback regulatory role in the digestive and metabolic processes regulated by peptides.

　　3, Endocrine system

　　Somatostatin can significantly inhibit the release of endocrine hormones in the gastrointestinal system, especially in the pancreas, including insulin, glucagon, gastrin, motilin, somatostatin, cholecystokinin, somatostatin-like peptide, and vasoactive intestinal peptide, etc. Somatostatin can inhibit the release of the above peptide hormones through specific or receptor-mediated actions, whether in normal tissue or tumor tissue.

　　The complex and diverse clinical manifestations of somatostatinoma make diagnosis very difficult, especially early diagnosis. If the patient has a triad of symptoms such as diabetes, cholelithiasis, and steatorrhea, as well as symptoms such as dyspepsia, hypochlorhydria, weight loss, abdominal pain, or abdominal mass.

　　1, Diabetes

　　Most patients with this disease will develop diabetes or decreased glucose tolerance, the severity ranging from slight elevation of blood glucose to significant ketonemia. The cause of diabetes is the secretion of large amounts of somatostatin by the tumor tissue, which inhibits the release of insulin. Some patients may have their insulin synthesis ability greatly restricted due to the replacement of the pancreas by tumor tissue.

　　2, Hypochlorhydria

　　Due to the inhibition of gastrin secretion and gastric acid secretion by somatostatin, all patients experience hypochlorhydria, and some patients even have achlorhydria. Patients present with symptoms of dyspepsia and upper abdominal fullness after eating.

　　3, Cholelithiasis

　　26-65% of patients may develop cholelithiasis, among whom about 16% of patients have jaundice of the skin and sclera. The possible cause of gallstone formation may be that somatostatin inhibits the release of cholecystokinin, inhibits the motility of the bile duct and gallbladder, and impairs lipid metabolism.

　　4, Abdominal pain

　　The incidence of abdominal pain is about 35%, and the pathogenesis includes malabsorption of nutrients, delayed gastrointestinal motility, tumor compression, or secondary infection.

　　5, Diarrhea

　　26% of patients with this disease have diarrhea, the cause is due to the absorption disorder of sugar, fat, and amino acids, which leads to increased osmotic pressure in the feces. Some patients may have steatorrhea. About 19% of patients with somatostatinoma experience steatorrhea due to the decreased exocrine function of the pancreas, leading to poor digestion and absorption of fats, thus causing the disease.

　　The most distinctive feature of somatostatinoma is its ability to secrete hormones easily, the etiology is unknown, the pathogenesis is not yet clear, there are no specific preventive measures at present, and the focus is mainly on early diagnosis and early treatment, and attention should be paid to hygiene and diet.

　　Somatostatinoma is a tumor derived from D cells in the islets of Langerhans, and its diagnostic methods include laboratory tests and localization diagnosis.

　　Firstly, laboratory examination

　　1. Gastric juice analysis

　　Insufficient gastric acid or even no gastric acid.

　　2. Blood sugar measurement

　　Increased blood sugar or decreased glucose tolerance test.

　　3. Basal plasma somatostatin measurement

　　It is the main basis for the diagnosis of this disease. Any patient suspected of having somatostatinoma should be measured for their plasma somatostatin levels. In the morning fasting state, the normal somatostatin level of a person

　　4. Provocation test

　　For patients suspected of having somatostatinoma clinically, but whose plasma somatostatin levels do not increase, further diagnosis can be made through provocative tests.

　　Secondly, localization diagnosis

　　1. Ultrasound, CT or MRI examination

　　Since the tumor mass of this disease is usually large, it is often possible to find the primary pancreatic tumor and liver metastatic tumor, and the rate of localization diagnosis is high.

　　2. Selective celiac arteriography

　　It can show the hemangioma of the pancreas and its liver metastasis, which has the same significance as B-ultrasound, CT and MRI in the localization diagnosis of the disease, and the diagnostic rate is greater than 85%. However, these examinations can only determine the existence of the tumor, but cannot make a qualitative diagnosis.

　　3. Gastrointestinal barium meal or duodenal hypotension contrast examination

　　For tumors located in the descending segment of the duodenum or the head of the pancreas, changes such as filling defects, expansion of the duodenal loop, and pressure marks can be seen, but these changes are not helpful for tumors located in the body and tail of the pancreas.

　　Somatostatinoma patients have no special dietary requirements. Patients can consult doctors specifically for different symptoms and formulate different dietary standards for specific diseases. The principle is to achieve a balanced diet and rich nutrition.

　　Surgical operation is the first choice for the treatment of somatostatinoma. However, due to the high metastasis rate of patients with this disease, the rate of surgical resection is not very high. Moreover, because most patients have large tumors, they are often not suitable for tumor excision, so pancreatectomy is the main surgical treatment effect.

　　Firstly, for tumors located in the body and tail of the pancreas, pancreatectomy of the body and tail of the pancreas can be performed.

　　Secondly, for tumors located at the head of the pancreas, subtotal pancreatectomy or pancreatoduodenectomy should be performed.

　　For giant tumors or liver metastatic tumors that cannot be resected radically, palliative resection can often achieve the purpose of alleviating symptoms and extending life.