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Galanin*

* Test available on a research basis only. Contact ISI for details.

 

Gastric Inhibitory Polypeptide*
(Glucose-Dependent Insulinotropic Peptide, GIP)

* Test available on a research basis only. Contact ISI for details.

 

Gastrin

Clinical Significance:
Gastrin is a peptide secreted in many molecular forms.  Gastrin is found in its main form (G-17) a smaller form G-14, "Big" Gastrin (G-34), and a larger "Big, Big" Gastrin.  This assay measures the G-17 and the G-14 forms of Gastrin.  The biological activity of Gastrin is contained in its last four amino acids. It is synthesized primarily in endocrine cells of the mucosa of the gastrin antrum and upper small intestine.  Gastrin stimulates secretion of acid by parietal cells of the gastric fundus and longer-term growth of the mucosa.  It increases contractility of smooth muscle of the lower esophagus and stomach.  Gastrin is released after a meal due to the action of specific amino acids.  Its release is inhibited by low gastric pH which sets up a negative feedback control system. In Atrophic Gastritis and Zollinger-Ellison's Syndrome, very high Gastrin levels are found.

Reference Range:
Up to 75 pg/ml

Procedure:
Gastrin is measured by direct radioimmunoassay.

Patient Preparation:
Patient should be fasting 10 - 12 hours prior to collection of specimen.  Antacid medications should be discontinued, if possible, for at least 48 hours prior to collection.

Specimen Collection:
3 ml serum should be collected and separated as soon as possible.  Freeze specimens immediately after separation.  Minimum specimen size is 1 ml.

Special Specimens:
For tumor/tissue and various fluids (i.e. CSF, peritoneal, synovial, etc.) contact the Institute for requirements and special handling.

Shipping Instructions:
Ship specimens frozen in dry ice.

References:
1. DG Bostwick and KG Bensch.  Gastrin Releasing Peptide in Human Neuroendocrine Tumors.  Journal of Pathology 146:  237, 1986.

2. JH Walsh, JI Isenberg, J Ansfield, and V Maxwell.  Clearance and Acid-Stimulating Action of Human Big and Little Gastrins in Duodenal Ulcer Subjects.  Journal of Clinical Investigation 57:  1125, 1976.

 

Gastrin Releasing Peptide*
(GRP)

* Test available on a research basis only. Contact ISI for details.

 

Ghrelin, Total
(Plasma)

Sensitivity:
Sensitivity is determined as the least amount of Ghrelin that can be distinguished from zero. The lower and upper limits of detection are 85 - 2400 pg/ml.

Patient Preparation:
Patient should be fasting for 10 - 12 hours prior to collection of specimen. Patient should not be on any medications or supplements that may influence: Cholecystokinin (CCK), Glucose, Growth Hormone, Insulin and/or Somatostatin levels, if possible, for at least 48 hours prior to collection.

Specimen Collection:
Collect 10mL blood in special ISI GI Preservative tube yielding special GI plasma and separate in refrigerated centrifuge as soon as possible. Transfer 3-5mL immediately into non-glass shipping vial. Minimum specimen size is 1mL. Freeze specimen at -20°C. Variance from these instructions must be disclosed to ISI prior to specimen analysis.

Shipping Instructions:
Ship specimens frozen in dry ice.

Reference Range:
By report.

References:
1. T Shiiya, M Nakazato, M Mizuta, Y Date, MS Mondal, M Tanaka, S Nozoe, H Hosoda, K Kangawa, S Matsukura. Plasma Ghrelin Levels in Lean and Obese Humans and the Effect of Glucose on Ghrelin Secretion. J Clin Endo Metab 2002; 87(1): 240-244.

2. DE Cumings, DS Weigle, RS Frayo, PA Breen, MK Ma, EP Dellinger, JQ Purnell. Plasma Ghrelin Levels After Diet-Induced Weight Loss or Gastric Bypass Surgery. N Engl J Med 2002; 346 (21): 1623-1630.

 

Glucagon

* Test available on a research basis only. Contact ISI for details.

 

Glucagon-Like Peptide 1 (GLP-1)

Reference Ranges:
Reference range is listed on individual patient test reports.

Procedure:
GLP-1 is measured by direct radioimmunoassay.

Patient Preparation:
The patient should be fasting for 10 to 12 hours prior to collection of specimen. Antacid medications and medications that affect intestinal motility or insulin secretion should be discontinued, if possible, for at least 48 hours prior to collection of specimen.

Specimen Collection:
Requirements: GLP-1(Total)*
Collect 10 mL blood in special tube containing the GI Preservative tube* available from ISI yielding plasma for GLP-1, (Total) and separate in refrigerated centrifuge as soon as possible. Transfer 3mL immediately to non-glass shipping vial and freeze plasma immediately after separation. Minimum specimen size is 1mL. Freeze specimen at -20°C. Special GI Preservative tubes are available from ISI.

Important Precaution:
GLP-1 specimens must be collected using ISI's G.I. preservative tube. No other specimens are acceptable.

Special Specimens:
For tumor/tissue and various fluids (e.g., CSF, peritoneal fluid, synovial fluid) contact ISI for requirements and special handling instructions.

Shipping Instructions:
Specimens should be shipped frozen in dry ice.

References:
1. Philippe J, Mojsov S, Drucker DJ, et al. Proglucagon processing in a rat islet cell line resembles phenotype of intestine rather than pancreas. Endocrinology. Dec;119(6):2833-9, 1986.

2. Weir GC, Mojsov S, Hendrick GK, et al. Glucagonlike peptide I (7-37) actions on endocrine pancreas. Diabetes. Mar;38(3):338-42, 1989.

3. Meier JJ, Nauck MA. Clinical endocrinology and metabolism. Glucose-dependent insulinotropic polypeptide/gastric inhibitory polypeptide. Best Pract Res Clin Endocrinol Metab. 18(4):587-606, 2004.

4. Nauck MA, Baller B, Meier JJ. Gastric inhibitory polypeptide and glucagon-like peptide-1 in the pathogenesis of type 2 diabetes. Diabetes. 53(Suppl 3):S190-6, 2004.

5. Drucker DJ. Glucagon-like peptides. Diabetes. 47(2):159-69, 1998.

6. Drucker DJ. Biological actions and therapeutic potential of the glucagon-like peptides. Gastroenterology. 122(2):531-44, 2002.

7. Lovshin J, Drucker DJ. Synthesis, secretion and biological actions of the glucagon-like peptides. Pediatr Diabetes. 1(1):49-57, 2000.

 


Gonadotropin Releasing Hormone
(Gn-RH, Luteinizing Hormone-Releasing Hormone LH-RH)

Clinical Significance:
Gonadotropin-Releasing Hormone (Gn-RH), also known as Luteinizing Hormone-Releasing Hormone (LH-RH), is a decapeptide secreted pulsatily from the hypothalamus.  It stimulates the release of the Gonadotropins - Luteinizing Hormone and Follicle Stimulating Hormone - exerting a stronger effect on Luteinizing Hormone.  Testosterone and Estradiol, whose release is stimulated by the Gonadotropins, exert a negative feedback control on LH-RH both at the hypothalamic site and by decreasing pituitary receptor binding.  LH-RH levels are low in patients with hypothalamic hypogonadism differentiating them from the high levels usually found in primary hypopituitary hypogonadism.  Accentuation of the LH-RH pulse occurs at the onset of puberty triggering the release of LH and FSH required in pubertal development.  LH-RH is stimulated by Epinephrine and suppressed by Dopamine and opiates.  LH-RH and some of its agonists are frequently used to induce ovulation.

Reference Range:
Male:                                  4.0 -   8.0 pg/ml
Female:                               2.0 - 10.0 pg/ml

Procedure:
Luteinizing Hormone-Releasing Hormone is measured by direct radioimmuno-assay.

Patient Preparation:
Patient should not be on any Steroid, ACTH, Gonadotropin, or Estrogen medications, if possible, for at least 48 hours prior to collection of specimen.

Specimen Collection:
3 ml serum or EDTA plasma should be collected and separated as soon as possible.  Freeze specimen immediately after separation.  Minimum specimen size is 1 ml.

Special Specimens:
For tumor/tissue and various fluids (i.e. CSF, peritoneal, synovial, etc.) contact the Institute for requirements and special handling.

Shipping Instructions:
Ship specimens frozen in dry ice.

References:
J Schopohl, G Mehltretter, R von Zumbusch, T Eversmann, and L von Werder.  Comparison of Gonadotropin-Releasing Hormone and Gonadotropin Therapy in Male Patients with Idiopathic Hypogonadism.  Fertility and Sterility 56: 1143-1150, 1991.

2. CB Lambalk, J Schoemaker, GP van Rees, J de Koning, and HAMJ van Dieten.  Exogenous versus Endogenous Pulses of Luteinizing Hormone-Releasing Hormone and Secretory Patterns of Gonadotropins.  Fertility and Sterility 56: 446-452, 1991.

 

Growth Hormone
(HGH, Somatotropin) *

* Test available on a research basis only. Contact ISI for details.

 

Growth Hormone Releasing Hormone (GH-RH)

Clinical Significance:
Growth Hormone Releasing Hormone is a 44 amino acid peptide produced primarily by the hypothalamus. It is a neurohumoral control for adenohypophyseal secretion of Growth Hormone.  Other hypothalamic hormones have a stimulatory effect on pituitary hormones, but Growth Hormone Releasing Hormone has no known effect on other pituitary hormones.  Somatostatin is the inhibitory counterpart of Growth Hormone Releasing Hormone.  Growth Hormone Releasing Hormone has structural similarities with the Secretin-Glucagon family of gastrointestinal hormones.  Growth Hormone Releasing Hormone has been isolated from pancreatic Islet Cells and various cancer tumor cells.

Reference Range:
5 - 18 pg/ml

Procedure:
Growth Hormone Releasing Hormone is measured by direct radioimmunoassay.

Patient Preparation:
Patient should not be on any medications that may influence pituitary secretion.

Specimen Collection:
3 ml serum or EDTA plasma should be collected and separated as soon as possible.  Freeze the plasma immediately after separation.  Minimum specimen size is 1 ml.

Special Specimens:
For tumor/tissue and various fluids (i.e. CSF, peritoneal, synovial, etc.) contact the Institute for requirements and special handling.

Shipping Instructions:
Ship specimens  frozen in dry ice.

References:
1. ML Vance.  Growth-Hormone-Releasing Hormone.  Clinical Chemistry  36: 415-420, 1990.

2, AM Sopwith, ES Penny, A Grossman, MO Savage, GM Besser, and LH Rees.  Normal Circulating Growth Hormone Releasing Factor (hGRF) Concentrations in Patients with Functional Hypothalamic hGRF Deficiency.  Clinical Endocrinology 24:   395-400, 1986

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