Somatostatin 

Updated: Mar 03, 2014
  • Author: Cory Wilczynski, MD; Chief Editor: Eric B Staros, MD  more...
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Reference Range

Somatostatin is a polypeptide that is released in the gastrointestinal tract by delta cells and the hypothalamus. It functions as a key regulatory peptide that has many physiologic effects as an inhibitor for many other hormones, including gastrin, cholecystokinin, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide, vasoactive intestinal peptide, 5-HT, and some anterior pituitary hormones.

The reference range for plasma somatostatin in adults is 10-22 pg/mL, the conversion factor is 0.426, and the SI units are 4.26-9.37 pmol/L. Draw in prechilled tube, separate plasma, and freeze immediately. [1]

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Background/Interpretation

Serum and cerebrospinal fluid (CSF) somatostatin values less than 100 pg/mL are within normal limits for healthy individuals. Decreased levels have been found to be seen in CSF in autopsy samples of people with Alzheimer disease. [2] No change was found in normal, younger subjects to suggest that this could be a predisposing laboratory screen for dementia patients. CSF values were also found to be elevated in young patients with febrile seizures. [3] Elevations in serum somatostatin are seen in somatostatinomas and neuroendocrine tumors. The levels are found to be on the scale of nanograms per milliliter, which is nearly 1000-fold greater than the standard unit. These tumors are very rare and slow-growing, but most patients are symptomatic. The following is the classic pentad of symptoms seen in a somatostatinoma syndrome: [4]

  • Cholelithiasis
  • Weight loss
  • Steatorrhea and diarrhea
  • Hypochlorhydria and achlorhydria
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Collection and Panels

Serum somatostatin

See the list below:

  • Specimen: Plasma
  • Condition: Fasting
  • Container: Lavender (EDTA; see image below) or pink (K 2 EDTA) pre-chilled tube
    Lavender-top tube. Lavender-top tube.
  • Collection method: Routine venipuncture
  • Processing: Separate plasma from cells within 2 hours of collection in lab; an adequate sample requires a minimum of 0.6-1.8 mL. If multiple samples need to be analyzed, the specimen should be kept frozen. Ambient temperatures and exposure to room air will make sample unacceptable for analysis. [5]

Cerebrospinal fluid somatostatin

See the list below:

  • Specimen: CSF
  • Collection method: Lumbar puncture
  • Typically part of same panel as CSF cell count, gram stain, albumin, glucose
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Background

Somatostatin is a polypeptide that is released in the gastrointestinal tract by delta cells and the hypothalamus. It functions as a key regulatory peptide that has many physiologic effects as an inhibitor for many other hormones, including gastrin, cholecystokinin, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide, vasoactive intestinal peptide, 5-HT, and some anterior pituitary hormones.

“The clinical usefulness of somatostatin is limited by its short half-life in the circulation (3 minutes) when it is administered by intravenous injection.” [6] Therefore, a synthetic preparation, octreotide, is used that mimics the properties of somatostatin. Octreotide is an octapeptide that can be given intravenously (30 min), subcutaneously (6-12 hours), or intramuscularly (monthly) for various applications. The most common indications for use include imaging for somatostatinomas, other neuroendocrine tumors, variceal bleeding, refractory diarrhea, and hypoglycemia. [6]

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