Copeptin

Copeptin
Diagram of the pre-pro-vasopressin precursor showing position and size in amino acids of AVP, neurophysin II and copeptin
Identifiers
Symbol	CT-proAVP
Alt. symbols	copeptine
OMIM	192340
UniProt	P01185
Other data
Locus	Chr. 20 p13

Copeptin (also known as CT-proAVP) is a 39-amino acid-long peptide derived from a pre-pro-hormone consisting of vasopressin, neurophysin II and copeptin. Arginine vasopressin (AVP), also known as the antidiuretic hormone (ADH), is involved in multiple cardiovascular and renal pathways and functions. However, vasopressin measurements are not commonly used in clinical practice because of the biochemical features of the molecule: its small size and very short half-life make vasopressin testing quite complicated and labor-intensive. On the other hand, copeptin can be immunologically tested with ease and therefore be used as a vasopressin surrogate.

Copeptin is a 39-amino acid-long, glycosylated peptide. It is synthesized mainly in the paraventricular neurons of the hypothalamus and in the supraoptical nucleus. During axonal transport, pre-pro-AVP is proteolytically cleaved into vasopressin, neurophysin II and copeptin. These molecules are then stored in secretory granules in the posterior pituitary and released upon osmotic or non-osmotic (hemodynamical; stress-related) stimuli.

Once secreted into the bloodstream, there is no known biological role for copeptin. However, when pre-pro-vasopressin is processed during the axonal transport, copeptin may contribute to the 3D folding of vasopressin.

The size and half-life of copeptin permit an easier immunological testing, compared to vasopressin, and hence copeptin is proposed as a reliable AVP surrogate. The clinical interest in copeptin testing is closely linked to the pathophysiological pathways in which vasopressin is involved : polydipsia-polyuria syndrome, hyponatremia, syndrome of inappropriate antidiuretic hormone secretion (SIADH) as well as heart failure and acute coronary syndrome.