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What is Copeptin?
Copeptin (or CT-proAVP), a 39-amino acid glycopeptide, is the C-terminal part of the prohormone of arginine vasopressin (AVP) or antidiuretic hormone (ADH).
The pre-pro-vasopressin precursor is synthesized and processed into its three components – AVP, Neurophysin II and Copeptin – within the hypothalamus; afterwards these products are transported along the neuronal axons in the granules of the posterior hypophysis (pituitary gland), where they are stored and released under appropriate stimulus.
Pathophysiology of Copeptin release
Pro-AVP, the precursor peptide of AVP and Copeptin, is produced and released by two endocrine mechanisms, which are distinct, but may have some anatomical interaction at the neuronal level.
Figure 1: AVP and Copeptin release in hypothalamus and pituitary gland and its effects
AVP/Copeptin release from posterior pituitary gland
When released by the posterior pituitary gland, the precursor peptide pro-AVP is produced in the magnocellular neurons of the supraoptic and paraventricular hypothalamic nuclei. During axonal transport through the infundibulum to the posterior lobe of the pituitary gland, AVP, Neurophysin II, and Copeptin are processed from the precursor peptide (see Figure 2).
Pro-AVP is subjected to a four-enzyme cascade to reach the bioactive conformation of mature AVP.Ref-1 During this process, Copeptin and Neurophysin II seem to help in the correct folding of AVP.Ref-1 Processing is usually complete at the level of the neurohypophysis.Ref-2 All three peptides are subsequently secreted from the neurohypophysis upon hemodynamic or osmotic stimuli; once released into circulation, AVP exerts its peripheral effects by binding to tissue-specific G-protein-coupled receptors (GPCR). The V1 receptor, which mediates arteriolar vasoconstriction and the V2 receptor, which is responsible for the antidiuretic effect of AVP in the kidney.
Figure 2: Arginine vasopressin (AVP) precursor peptide (numbers indicate the amino acid positions of the pre-pro-hormone)
AVP/Copeptin release from anterior pituitary gland
When released by the anterior pituitary gland, the precursor peptide is synthesized and processed in the parvocellular neurons of the hypothalamus, an area where releasing hormones, such as corticotropin-releasing hormone (CRH), are also produced. AVP produced by this mechanism is subsequently released into the pituitary portal system at the eminentia mediana and acts immediately on the endocrine cells of the adenohypophysis, by binding to its V3 (V1b)-receptor. The complex stimulation of the humoral stress response, resulting in adrenocorticotropic hormone (ACTH) and cortisol release, has been attributed to a synergistic effect of CRH and AVPRef-3-6 This redundant or “backup” system of two hormones from the hypothalamus for the release of ACTH underlines the physiologic importance of the endocrine stress response.
Copeptin - The stable surrogate marker of vasopressin (ADH)
AVP is a key hormone, with important physiological functions, including vascular tonus, the homeostasis of fluid balance, and regulation of the endocrine stress response.7 However, due to the inherent instability of AVP and technical limitations, measurements of vasopressin concentrations have proven difficult.
Copeptin is more stable and can be easily measured, making it a very reliable surrogate marker for vasopressin.
Figure 3: Copeptin’s stability at room temperature8
citrate plasma cannot be measured with KRYPTOR, data shown are LIA data
Advantages: overcome AVP limitations with Copeptin measurements
Stable
Extremely high stability ex vivo
<20% loss of analyte has been shown for at least 7 days at room temperature.8
Reliable
Not significantly bound to platelets
Helps to avoid falsely elevated or varying measurements of free plasma AVP8
Easy to measure
Sensitive automated immunoassay
Thermo Scientific B·R·A·H·M·S Copeptin proAVP KRYPTOR Assay is available on our fully automated bench-top analyzers
Precise
Correlates better with serum osmolality than vasopressin itself
Copeptin helps to better evaluate response to osmotic and hemodynamic changes. 9
Convenient
Increased ease and speed
B·R·A·H·M·S Copeptin proAVP KRYPTOR helps to improve the diagnosis of AVP-dependent fluid disorders. 10-12
Quick
Fast turnaround time
Results are available in less than 30 minutes
Product specification
Features |
B·R·A·H·M·S Copeptin proAVP KRYPTOR |
Assay format |
Automated immunofluorescence assay (KRYPTOR) |
Technology |
Time Resolved Amplified Cryptate Emission (TRACE) |
Direct measurement |
2.7-500 pmol/L |
Measuring range with automatic dilution |
2.7-2,000 pmol/L |
Functional assay sensitivity (FAS) |
<1.08 pmol/L |
Detection limit |
0.88 pmol/L |
Incubation time |
14 minutes |
Sample volume |
50 µL |
Sample type |
Serum, plasma (EDTA, heparin) |
Determinations |
50 |
B·R·A·H·M·S Copeptin proAVP KRYPTOR kit and accessories
Article number |
Description |
857050N |
B·R·A·H·M·S Copeptin proAVP KRYPTOR |
085791N |
B·R·A·H·M·S Copeptin proAVP |
085792N |
B·R·A·H·M·S Copeptin proAVP |
Diverse clinical uses for the Copeptin lab test
Early rule-out of Acute Myocardial Infarction (AMI)
Safe and early rule-out of chest pain patients with suspected AMI using Copeptin in combination with troponin
Diabetes insipidus (AVP deficiency) after neurosurgery
Early goal-direct management of patients undergoing pituitary surgery using Copeptin
Polyuria-polydipsia syndrome
Differential diagnosis of AVP resistance, AVP deficiency and primary polydipsia using Copeptin
High-quality B·R·A·H·M·S KRYPTOR immunoassays help provide exceptional intra-and interassay precision due to homogenous assay design without any washing or separation step. This extraordinary precision supports confident decision making on clinical status and further diagnostic measures for optimal patient management.
References:
- Acher R et al. J Mol Neurosci. 2002;18:223–228.
- Repaske DR et al. J Clin Endocrinol Metab. 1997;82:51–56.
- Gillies GE et al. Nature. 1982;299:355–357.
- Rivier C et al. Nature. 1983;305:325–327.
- Rivier C et al. Endocrinology. 1983;113:939–942.
- Milsom SR et al. Clin Endocrinol (Oxf). 1985;22:623–629.
- Morgenthaler et al. UNI-MED. 2015. Copeptin – Biochemistry and Clinical Diagnostics.
- Morgenthaler et al. Clin Chem. 2006.
- Balanescu et al. J Clin Endocrinol Metab. 2011.
- Fenske et al. J Clin Endocrinol Metab. 2011.
- Timper et al. J Clin Endocrinol Metab. 2015.
- Christ-Crain & Fenske. Nat Rev Endocrinol. 2016.
*data shown are LIA data
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