Clinical Chemistry Blog Notes 05

It is considered to be a hypothalamic hormone that inhibited growth secretion. It inhibits the pituitary (growth hormone and thyrotropin), gastrointestinal (gastrin, secretin, vasointestinal peptide) and pancreatic (insulin, glucagon) hormones as well as possesses nonendocrine functions (e.g., inhibition of gastric acid secretion, gastric emptying time and pancreatic enzyme release). It affects neurotransmission and cell proliferation by interacting with the G-protein-coupled somatostatin receptors and by inhibiting the release of numerous secondary hormones.

In the pancreatic islets, somatostatn is produced on the delta cells, which comprise 5-10% of the islet cells. Rare islet tumors, somatostinomas, secrete high levels of somatostastin. Elevated somatostatin levels can also be seen in small cell lung cancer, medullary thyroid cancer and pheochromocytoma.

Reasons why a test need to be performed:

• Detect growth deficiencies and abnormalities, including delayed puberty and small stature in adolescents
  
• Helps in the diagnosis of hyperpituitarism that is evident in gigantism or acromegaly
  
• Screen for inadequate or reduced pituitary gland function
  
• Assist in the diagnosis of pituitary tumors or tumors related to the hypothalamus
  
• Evaluate hGH therapy.

Test: Serum Somatostatin

Method: RIA (Radioimmunoassay)
RIA is a laboratory method that measures minute amounts of a substance, such as a hormone or drug, by quantitating the binding, or the inhibition of binding, of a radiolabeled substance to an antibody.

Use: to detect Somatostatinoma , detect growth deficiencies and abnormalities, diagnosis of hyperthyroidism, diagnosis of pituitary hormones

Somatostatinoma- It is a tumor of the delta cells of the endocrine pancreas that produces somatostatin. It is a rare gut neuroendocrine tumors. It is associated with diabetes mellitus , abnormal glucose tolerance and diarrhea with steatorrhea.

References:

-Henry's Clinical Diagnosis and Management by Laboratory Methods 21st Edition, Richard A. McPherson and Matthew R. Pincus

-http://findarticles.com/p/articles/mi_g2601/is_0006/ai_2601000608/

http://www.answers.com/topic/radioimmunoassay

Photo:

www.daviddarling.info/encyclopediaS/somatostatin.html

www.smj.org.uk/0508/soma%20cr4.htm