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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

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

 

Gastrin Releasing Peptide*
(GRP)

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

 

Ghrelin, Total
(Plasma)

Clinical Significance:
Clinical Significance: Ghrelin is a novel 28 amino acid peptide derived by post-translational processes from a preproghrelin consisting of 117 residues, secreted by the stomach with specific receptors in the brain involved in appetite regulation. It conveys information to the brain thereby increasing appetite, food intake and body weight and influences the release of growth hormone. Ghrelin is a growth hormone-releasing peptide which acts as an endogenous ligand of the growth hormone secretagogue receptors (GHS-Rs). Ghrelin levels are inversely correlated with body weight and are higher during weight loss.

Reference Range:
By report.

Procedure:
Ghrelin is measured by EIA/ELISA following extraction of specimens.

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.

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.

Shipping Instructions:
Ship specimens frozen in dry ice.

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) *

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

 


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 EIA/ELISA.

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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