Adrenocorticotropic Hormone
Label Mnemonic: ACTH
Epic Lab Code: LAB511
Downtime Form: A-1a General Laboratory Requisition
Chemistry
6240 RCP
356-3527
Specimen(s):
Plasma
Specimen Instructions:
Specimen must be delivered to laboratory within two hours of collection or alternatively have been frozen within two hours of collection.1 If shipping frozen samples, the plasma first needs to be separated from the cells, frozen immediately, and then shipped on dry ice. Frozen whole blood specimens are not acceptable.

Testing cannot be added on. Samples that have already gone through a freeze-thaw cycle prior to delivery to laboratory are also not acceptable.
Collection Medium:
Pink top tube 6 mL (K2-EDTA)
Alternate Collection Media:
Lavender top tube 3 mL (EDTA)
Minimum:
3 mL whole blood in pink tube or TWO Microtainer® devices.
Rejection Criteria:
Due to limited stability, add-on orders for ACTH are not accepted. Samples that have gone through a freeze-thaw cycle are also not acceptable.
Delivery Instructions:
Deliver to laboratory immediately after collection.
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
1 hour (upon receipt in laboratory)
Reference Range:
Serum/Plasma Normal Range
1 week - 9 years:    5-46 pg/mL
10-18 years:         6-55 pg/mL
19 years and older:  7-63 pg/mL
Interpretive Data:
The assay has minimal (< 2%) cross-reactivity with synthetic ACTH medications including Cosyntropin (Cortrosyn® or generic equivalent) which contains only the first 24 amino acids of ACTH.
Comments:
Adrenocorticotropic hormone (ACTH) or corticotropin is a peptide hormone consisting of 39 amino acids. It is produced in the anterior pituitary of the brain as part of the precursor molecule pro- opiomelanocortin (POMC). Tissue-specific cleavage results in ACTH and a range of related peptides.2,3 ACTH stimulates formation and secretion of glucocorticoids (especially cortisol) by the adrenal cortex. The glucocorticoid production is regulated by various factors.4 After stimulation (e.g. by physical effort or by the internal body clock), the hypothalamus secretes CRH (corticotropin releasing hormone). CRH acts on the pituitary, which in turn synthesizes and secretes ACTH. Finally, ACTH stimulates secretion of the glucocorticoids by the adrenals.

High concentrations of glucocorticoids in the blood inhibit secretion of CRH and ACTH via a negative feedback mechanism. ACTH concentrations show a diurnal variation with high levels in the morning and low levels in the evening. Therefore, as with cortisol, it is important to know the collection time of the plasma sample for interpretation of the results. Plasma ACTH measurements are useful in the differential diagnosis of pituitary Cushing's disease (ACTH hypersecretion), autonomous ACTH-producing pituitary tumors, hypopituitarism with ACTH deficiency and ectopic ACTH syndrome.5,6 In addition to cortisol measurements, ACTH determinations can be used together with functional or stimulation tests to diagnose the origin of glucocorticoid overproduction. Similarly, ACTH measurements can be employed to facilitate differential diagnosis of adrenocortical insufficiency (Addison's disease). ACTH not produced by the pituitary gland is known as ectopic ACTH. This is often associated with small cell carcinoma of the lung. In rare cases ectopic ACTH can be caused by thymic tumors, pancreatic adenocarcinomas, or bronchial carcinoids.

The Roche Diagnostics Elecsys ACTH assay employs two monoclonal antibodies specific for ACTH (9-12) and for the C-terminal region (ACTH 36-39). Due to common antigenic structure, the antibodies recognize intact biologically active ACTH 1-39 and the ACTH precursors POMC and pro-ACTH.3

References:
1. Reisch N, Reincke M, Bindlingmaier M.  Preanalytical stability of 
adrenocorticotropic hormone depends on time centrifugation rather than 
temperature.  Clin Chem 2007;53:358-359.

2. Cone RD. Anatomy and regulation of the central melanocortin system. 
Nature Neurosci 2005;8:571-578.

3. Talbot JA, Kane JW, White A. Analytical and clinical aspects of 
adrenocorticotrophin determination. Ann Clin Biochem 2003;40:453-471.

4. Jacobson L. Hypothalamic-pituitary-adrenocortical axis regulation. 
Endocrinol Metab Clin North Am 2005;34:271-292.

5. Beauregard C, Dickstein G, Lacroix A. Classic and recent etiologies 
of Cushing's syndrome: diagnosis and therapy. Treat Endocrinol 
2002;1:79-94.

6. Lindsay JR, Nieman LK. Differential diagnosis and imaging in 
Cushing's syndrome. Endocrinol Metab Clin North Am 2005;34:403-
421.
Test Limitations:
Icterus: No significant interference up to an icteric index of 25 (approximate conjugated and unconjugated bilirubin concentration: 25 mg/dL).

Hemolysis: No significant interference up to an hemolytic index of 400 (Hb is less than 400 mg/dL).

Lipemia: No significant interference up to an lipemic index of 1500.
Methodology:
Electrochemiluminescence Immunoassay
CPT Code:
82024
 
See Additional Information:
Specimens Requiring Immediate Delivery