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C-Peptide*

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

 

C-Peptide, urine*

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

 

Calcitonin
(Thyrocalcitonin)*

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

 

Cholecystokinin (CCK)

Clinical Significance
Cholecystokinin is a 33 amino acid peptide having a very similar structure to Gastrin.  Cholecystokinin is present in several different sized forms including a 58 peptide Pro-CCK and 22, 12, and 8 peptide metabolites.  The octapeptide retains full activity of the 33 peptide molecule.  Cholecystokinin has an important physiological role in the regulation of pancreatic secretion, gall bladder contraction and intestinal motility.  Cholecystokinin levels are elevated by dietary fat especially in diabetics.  Elevated levels are seen in hepatic cirrhosis patients.  Cholecystokinin is found in high levels in the gut, in the brain and throughout the central nervous system.

Reference Range
Up to 80 pg/mL

Procedure
CCK is measured by direct radioimmunoassay.

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

Specimen Collection
Collect 10 mL EDTA plasma in a special tube containing the GI Preservative and
separate as soon as possible. Freeze plasma immediately after separation. Special GI
Preservative tubes are available from ISI. Minimum specimen size is 1 mL.

Important Precaution
CCK specimens must be collected using the GI 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. Nakano I, Funakoshi A, Shinozaki H, et al. Plasma cholecystokinin and pancreatic polypeptide responses after ingestion of a
liquid test meal rich in medium-chain fatty acids in patients with chronic pancreatitis. Am J Clin Nutr. Feb;49(2):247-51,
1989.
2. Chang T, Chey WY. Radioimmunoassay of cholecystokinin. Dig Dis Sci. May;28(5):456-68, 1983.
3. Rehfeld JF. Clinical endocrinology and metabolism. Cholecystokinin. Best Pract Res Clin Endocrinol Metab. 18(4):569-86,
2004.

CPT Code: 
Unspecified
Quantitative
Immunoassay  83519

 

Chromogranin A (CGA)*

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

Corticosterone*
(Compound B)

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

 

Corticosterone, urine*
(Compound B)

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

 

Corticotropin Releasing Factor
(CRF, CRH)

Clinical Significance
Corticotropin Releasing Factor is a 41 amino acid peptide produced in the hypothalamus.  It stimulates the release of ACTH from the pituitary which in turn releases Cortisol from the adrenal gland.  The Cortisol produced rapidly shuts off CRF secretion acting as a negative feedback control.  CRF also releases b-Endorphin, b-Lipotropin and other related proopiomelanocortin peptides.  Ectopic tumors producing ACTH also frequently produce CRF.  In these patients ACTH usually does not respond to Dexamethasone suppression. CRF is markedly elevated in third trimester pregnancy.  Most of it is produced by the placenta and is bound to CRF-Binding Protein and is biologically inactive.  The CRF stimulation test is the most effective method of differentiating primary from secondary adrenal insufficiency and in differentiating hypothalamic from pituitary causes.

Reference Range
Up to 10 pg/ml

Procedure
Corticotropin Releasing Factor is measured by direct radioimmunoassay.

Patient Preparation
Patient should be fasting 10 - 12 hours and should not be on any corticosteroid, ACTH, or estrogen medications, if possible, for at least 48 hours prior to collection of specimen.  An am specimen is preferred.

Specimen Collection
3 ml EDTA plasma should be collected and separated as soon as possible.  Plasma should be frozen 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. Jones SA, Brooks AN, and Challis JRG.  Steroids Modulate Corticotropin-Releasing Hormone Production in Human Fetal Membranes and Placenta.  J Clin Endocrinol and Metab 68: 825-830, 1989

2. Vigh S, Merchenthaler I, Torre-Aleman I, et al. Corticotropin Releasing Factor (CRF): Immunocytochemical Localization and Radioimmunoassay (RIA).  Life Sci 31: 2441, 1982.

CPT Code: 
Corticosterone  82528

 

Cortisol
(Compound F, Hydrocortisone)

Clinical Significance
Cortisol is the major corticosteroid produced by the adrenal gland by hydroxylation of 11-Deoxycortisol.  It is reversibly converted to Cortisone and is excreted in the urine as its Sulfate and Glucuronide, free (unconjugated) and as TetrahydroCortisol.  Cortisol production is controlled by ACTH.  Cortisol exerts a dual negative feedback control of ACTH by decreasing Corticotropin Releasing Hormone release and blocking pituitary release of ACTH.  Cortisol is strongly bound to Corticosteroid Binding Globulin, loosely bound to Albumin, and a small amount is "Free" non-protein bound.  Cortisol exhibits a wide diurnal variation with highest levels in the morning hours and decreasing by the late afternoon.  Absence of the diurnal variation is a good indicator for Cushing's syndrome.  Cortisol levels are stimulated by Estrogens, Hyperthyroidism, ACTH and Corticotropin Releasing Hormone.  Cortisol is suppressed by chronic renal failure, nephrotic syndrome, starvation, Dexamethasone and Metapyrone.

Reference Ranges
8:00 am:                                    8 - 24 ug/dl
4:00 pm:                                    4 - 10 ug/dl

Procedure
Cortisol is measured by direct radioimmunoassay.

Patient Preparation
Patient should not be on any Corticosteroid, ACTH, Thyroid 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.  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 at room temperature or frozen in dry ice.

References
1. Meulenberg PMM and Hofman JA. Differences between Concentrations of Salivary Cortisol and Cortisone and of Free Cortisol and Cortisone in Plasma during Pregnancy and Postpartum.  Clin Chem 36:70-75, 1990.

2. Oka K, Noguchi M, Kitamura T, and Shima S. Liquid Chromatography and Radioimmunoassay Compared for Determination of Cortisol and Corticosterone in Plasma after a Dexamethasone Suppression Test.  Clin Chem 33:1639-1642, 1987.

CPT Code: 
Cortisol  82533

 

Cortisol, Saliva
(Compound F, Hydrocortisone)

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

 

Cortisol, urine*
(Compound F, Hydrocortisone)

* Test will be discontinued as of July 1, 2013 and specimens will not be accepted after June 15th, 2013. Contact ISI for details.

 

Cortisone, urine*
(Compound E)

* Test will be discontinued as of July 1, 2013 and specimens will not be accepted after June 15th, 2013. Contact ISI for details.

 

Cortisol Binding Globulin*
(CBG, Transcortin)

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

 

Cortisol Binding Globulin Index *
(CBG-I)

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

 

Cortisone*
(Compound E)

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

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