A of metabolic illnesses known as diabetes includes polyuria, polydipsia, and weight loss. Diabetes mellitus (DM) is a metabolic disorder marked by impaired glucose homeostasis that causes blood sugar to rise owing to insufficient insulin production, insulin action defects, or both (1). Two etiopathogenetic types account for the majority of diabetes cases. The first is type 1 diabetes, which is brought on by a complete lack of insulin secretion. The second is type 2 diabetes mellitus, which has both insulin action resistance and inadequate compensatory insulin production as its causes. Even before obvious fasting hyperglycemia manifests in type 2 diabetes, pathologic and functional alterations in several tissues may already be present in the early stages of aberrant glucose metabolism (2).

Another type of diabetes is diabetes insipidus characterized by inadequate arginine vasopressin (AVP) synthesis or efficacy, resulting in hypotonic polyuria that is accompanied by compensatory polydipsia. The role of AVP has been reported among the causes of type 2 diabetes (3).

Copeptin and AVP are both descended from the same progenitor molecule. Copeptin and AVP have a very significant correlation; it reacts to osmotic, hemodynamic, and general stressful stimuli just as quickly as AVP. The physiological functions of homeostasis of fluid balance, regulation of vascular tone, and control of endocrine stress are roles of AVP, whereas the purpose of copeptin is yet uncertain (4).

The 39-amino acid copeptin is created from the C-terminal of the precursor arginine vasopressin (AVP). AVP, neurophysin II, and copeptin are all produced in equimolar levels from the AVP precursor. Additionally, a strong connection between the release of AVP and copeptin was observed (5). Measurement of AVP concentration remains complicated since AVP is an unstable peptide and, additionally, it is bound by platelets. Compared with AVP, copeptin is more stable because it remains stable in serum or plasma for several days and has greater testability since copeptin findings are accessible in 1 h (6) and at room temperature (4) (Figure 1). Consequently, the quantity of copeptin might serve as a perfect replacement to reflect the level of AVP (7).

The first section of this review will be devoted to the structure, physiology, and role of copeptin. Second, the main focus will be on how copeptin may be used as a diagnostic and prognostic marker for various disorders associated with diabetes.

Vasopressin is generated from the same precursor peptide (pre-pro-vasopressin) as arginine copeptin and vasopressin (AVP). Physiological factors induce both peptide changes that are comparable to conditions, such as osmotic stimulation, hypovolemia, or stress (8).

Conditions, median Copeptin plasma levels in healthy volunteers at baseline were found to be 4.2 pmol/L, with a wide range of 1–13.8 pmol/L and slightly higher values in men than women. Copeptin levels do not vary with time of day or with age. Consumption of meals and the menstrual cycle do not appear to have any impact on copeptin release. (9).

Copeptin is rapidly removed from the circulation by bioactive peptides rather than accumulating there, and this fast clearance no longer takes place ex vivo. Copeptin appears to be either broken down by tissue-bound proteases or quickly excreted by the liver or kidneys. However, no specific copeptin receptor or copeptin removal mechanisms are currently understood (10).

While the precise physiological role of copeptin per se is largely unclear, the physiological functions of AVP include controlling vascular tone, fluid balance, and the endocrine stress response (11). However, it was asserted that the chaperone-like molecule copeptin is crucial for the structural development of pro-AVP and may play a role in the proper folding of the precursor molecule pre-pro-AVP by acting on the glycosylation pattern (5).

Copeptin’s clinical significance as an AVP marker is based on the fact that both AVP and copeptin are released simultaneously after being transported from the hypothalamus to the posterior pituitary.

According to data obtained from Google Scholar and the PubMed database, the measurement of copeptin in sera might serve as an important marker for assessing the risk of complications as well as outcomes in several diseases in general medicine, where vasopressinergic disturbances may play a role in the pathogenesis (4).

Polyuria polydipsia syndrome is a term used to describe several illnesses, and hypotonic polyuria is eventually either a result of inadequate AVP production effectiveness or is frequently accompanied by compensatory polydipsia. That syndrome falls into one of three categories: First, because of inadequate AVP production in response to osmotic stimulation, central diabetes insipidus (CDI) develops. Second, renal insensitivity to typical AVP secretion is the cause of nephrogenic diabetes insipidus (NDI). Third, primary polydipsia persists despite intact AVP secretion and a favorable renal response (PP) involving excessive fluid intake per se that can produce polyuria (3).

The water deprivation test, which has since been supplanted by the hypertonic saline test plus copeptin measurement or arginine-stimulated copeptin measures, was the commonly acknowledged test for decades as a possible differential diagnosis for polyuria and polydipsia. To differentiate between nephrogenic and central diabetes insipidus, copeptin levels may be simply assessed. Copeptin dependably differentiates several entities of polyuria polydipsia syndrome; baseline levels >20 pmol/L without preceding fluid deprivation classify patients with nephrogenic diabetes insipidus, whereas levels measured upon osmotic stimulation with hypertonic saline or upon non-osmotic stimulation with arginine differentiate primary polydipsia from central diabetes insipidus (10). (Figure 2 Copeptin as a marker in metabolic disorders.)

Copeptin regularly reflects blood AVP concentrations and is released at equimolar levels to AVP. Since copeptin is stable ex vivo, is simple to test, and yields findings in an hour, copeptin measurement offers a number of benefits over AVP. Recently, copeptin has been suggested as a potential marker for the differential diagnosis of polyuria-polydipsia syndrome. Copeptin may be useful to serve as a marker for the development of metabolic disorders such as metabolic syndrome, diabetes, and liver conditions.