Test Overview
Direct RIA
Somatostatin is a cyclic peptide originally isolated from sheep hypothalami and shown to inhibit the release of Growth Hormone. Somatostatin is present primarily in three main forms: a 14 amino acid peptide, a 28 amino acid peptide ("Big" Somatostatin), and a 12,000 molecular weight ProSomatostatin. This assay measures only the 14 amino acid form of Somatostatin. All three forms of Somatostatin have similar biological properties and overall potencies. Somatostatin is a physiological regulator of Islet Cell and gastrointestinal functions, and is a suppressor of many pituitary hormones including Growth Hormone, Prolactin, and Thyrotropin (TSH). Somatostatin levels are often elevated in diabetics, but the levels return to normal upon correction of the hormonal and metabolic deficiencies present. In many cases of APUDomas including VIPoma, Insulinoma, Glucagonoma, and Gastrinoma, elevated levels of Somatostatin are found.
< 25 pg/mL
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
Test Details
9 - 11 days
- Somatotropin Release Inhibiting Factor
Specimen Requirements
Either EDTA lavender top tube, or GI Preservative tube are acceptable.
Collect specimen in EDTA lav top tube. For baseline determination collect specimen following an overnight (10-12 hour) fast. Following collection, centrifuge, aliquot plasma into a plastic vial, and freeze. If possible, discontinue insulin medication prior to collection.
Fasting specimen. EDTA lavender top tube is now preferred, but special "G.I. Preservative" tube is acceptable. (Stored in the refrigerator in Sendouts)
Additional Information
Test sent to Mayo Medical Laboratories; performed by Interscience Institute.