copeptin

Copeptin is a 39-amino-acid peptide that comprises the C-terminal portion of provasopressin, the precursor to the neurohypophysial hormone vasopressin (antidiuretic hormone). It is produced and released from the posterior pituitary in equimolar amounts with vasopressin in response to the same physiological stimuli, such as increased plasma osmolality or decreased blood volume. Unlike vasopressin, copeptin is chemically stable in blood, making it a practical surrogate biomarker for vasopressin release.

Because copeptin mirrors vasopressin secretion but is far more stable and easier to measure, it is routinely assessed by immunoassays in plasma or serum. This stability facilitates sample handling and storage, and copeptin testing can provide rapid information in acute settings.

In clinical practice, copeptin is used primarily as a prognostic and diagnostic aid in acute illness. In suspected myocardial infarction, copeptin measured at presentation alongside cardiac troponin can improve early risk stratification and aid in rule-out decisions. In sepsis and septic shock, elevated copeptin levels correlate with severity and can help predict outcomes. High copeptin has also been associated with worse prognosis after stroke or acute kidney injury. Because copeptin is not disease-specific, its interpretation depends on the clinical context and other diagnostic data.

Limitations include its elevation in a wide range of acute stress states, which can limit specificity. Standardized reference ranges and assay-specific cutoffs vary, so results should be interpreted with awareness of the testing method and patient factors.

Related topics include vasopressin and provasopressin.