Copeptin in the differential diagnosis of hypotonic polyuria

Oral Levodopa Stimulates Copeptin Secretion in Children and Adolescents with Intact Posterior Pituitary Function

BACKGROUND

Copeptin stimulation tests can be used in the differential diagnosis of polyuria polydipsia syndrome. Current stimulation methods rely on intravenous or subcutaneous administration. Oral stimulus can further simplify the diagnostic approach. The levodopa stimulation test is widely used in the evaluation of growth hormone deficiency (GHD), and the dopamine pathway was reported to be associated with arginine vasopressin secretion. The study aimed to investigate the effect of oral levodopa on copeptin secretion.

METHODS

The study was a prospective observational single-center cohort study. Patients < 18 years old with short stature and no symptoms of polyuria or polydipsia undergoing levodopa stimulation test for suspected GHD were recruited from May 2023 to Nov 2023. Copeptin and growth hormone (GH) were measured at 0, 30, 60, 90, and 120min in the levodopa test. The insulin tolerance test with copeptin and GH measured at the same time points was conducted in part of patients.

RESULTS

Forty-four participants were included in the final analysis. In the levodopa stimulation test, the median (interquartile range, IQR) copeptin concentration increased from 5.20 (3.51, 8.25) pmol/L to maximum 19.36 (8.97, 108.08) pmol/L (P < 0.001), 3.94 (1.41, 13.88) times of the baseline (P < 0.001). Compared with insulin tolerance test, peak copeptin in the levodopa test was significantly higher (34.61 (13.67, 98.96) vs 8.88 (7.14, 15.42) pmol/L, P = 0.009). Higher copeptin was associated with larger dose of levodopa.

CONCLUSIONS

Oral levodopa could be used to stimulate copeptin.

Arginine-Stimulated Copeptin-Based Diagnosis of Central Diabetes Insipidus in Children and Adolescents

INTRODUCTION

Diagnosis of central diabetes insipidus (CDI) remains challenging. Water deprivation testing and hypertonic saline infusion, as established diagnostic tests, are mentally and physically demanding for patients. Arginine-stimulated copeptin has been shown as a putative parameter for the differential diagnosis of CDI in adults.

METHODS

In this single-centre retrospective study, we identified paediatric patients with suspected pituitary disorders who underwent standard arginine testing. Patients with CDI, matched controls, and primary polydipsia (PP) were identified. Diagnoses were confirmed retrospectively using comprehensive clinical and diagnostic characteristics. Serum copeptin concentrations were measured using a commercially available automated immunofluorescence assay (B.R.A.H.M.S Copeptin-proAVP KRYPTOR®) in samples stored for a median of 4.6 years (1.3-10.84) and collected before and 60 min after arginine infusion. Cut-off analyses were performed using ROC curves.

RESULTS

Serum samples from 32 patients with CDI, 32 matched controls, and 5 patients with PP (n = 69; 51 males, 18 females) were available for analysis. Median copeptin concentrations increased from 4.47 pmol/L (interquartile range [IQR]: 3.47-8.36) to 6.96 pmol/L (IQR: 4.51-12.89; p < 0.001) in controls, from 1.46 pmol/L (IQR: 1.21-2.12) to 1.44 (IQR: 1.10-1.87; p = 0.645, ns) in CDI, and from 4.40 pmol/L (3.95-6.33) to 9.58 pmol/L (8.19-11.42; p < 0.001) in PP. The published cut-off value of 3.8 pmol/L revealed a sensitivity of 100% and a specificity of 86.5% in confirming CDI.

CONCLUSION

Our results suggest that arginine-stimulated serum copeptin concentrations are a sensitive and specific diagnostic tool for CDI in paediatric patients, which may replace and simplify the conventional diagnostic pathway of water deprivation testing and hypertonic saline infusion.

Copeptin levels in hospitalized infants and children with suspected vasopressin-dependent disorders: a case series

OBJECTIVES

There have been recent advances assessing copeptin levels in adults with suspected disorders of vasopressin release. Very limited data exits on copeptin levels in children and infants, especially in a critically-ill hospitalized population where hyper- and hypo-natremia are very common. Our objective is to describe the institutional experience assessing copeptin levels in hospitalized infants and children with hyper- or hypo-natremia.

METHODS

We performed a single-center retrospective case series of all infants, children, and adolescents who had an ultrasensitive plasma copeptin level obtained between 2019-2021.

RESULTS

A total of 29 critically ill patients (6 infants) were identified with 38 % of patients having copeptin levels after neurosurgical procedures for tumors or trauma. Approximately 13/17 children with hypernatremia had CDI to diagnose CDI, A copeptin level ≤ 4.9 pmol/L resulted in an 88 % sensitivity (95 % CI 47-99 %), and 66 % specificity (95 % CI 30-93 %). Amongst those with hyponatremia levels were more variable, 8/12 children had SIAD with copeptin levels ranging 4.7-72.6 pmol/L.

CONCLUSIONS

While difficult to conclude due to multiple limitations, this case series highlights that typical copeptin cutoffs used to diagnose DI in adults in an ambulatory setting may also translate to a critically-ill pediatric population. Large prospective studies are needed to confirm this observation. In addition, postoperative copeptin levels could potentially be utilized as an additional marker to predict permanent from transient DI, but much larger studies are needed. Further work is needed to establish normative copeptin levels in infants and patients with SIAD.

Severe hyponatremia due to water intoxication in a child with sickle cell disease: A case report

Water intoxication is a potentially fatal hypo-osmolar syndrome with brain function impairment. Isolated symptomatic excessive ingestion of free water is very rare in childhood. We report a case of acute hyponatremia due to water intoxication without Antidiuretic Hormone (ADH) excess in a child with sickle cell disease. The boy was admitted to our Emergency Department because of new-onset prolonged generalized seizures. Blood test showed hyponatremia, and elevated creatine kinase value; neuroimaging was negative. His recent medical history revealed that on the day before he had drunk about 4 liters of water in 2 hours to prevent sickling, because of back pain. He was treated with mild i.v. hydration with normal saline solution and showed progressive clinical improvement and normalization of laboratory test. Rhabdomyolysis is a rare complication of hyponatremia whose underlying mechanism is still unclear.

Copeptin: a neuroendocrine biomarker of COVID-19 severity

Aim: To investigate the change in a serum level of copeptin, a neuroendocrine biomarker, in differentiating grades of COVID-19 severity on admission time and to find its diagnostic potential. Materials & Methods: 160 COVID-19 patients were classified according to disease severity into 80 mild to moderate and 80 severe patients. Serum copeptin level was assessed by ELISA on their admission time. Besides, serum CRP, ferritin and D-dimer were estimated. Results: Severe COVID-19 patients showed higher serum copeptin level in comparison to mild to moderate cases, with diagnostic potential to distinguish disease severity with 93.33% sensitivity and 100% specificity at cutoff value >18.5 Pmol/l. Conclusion: Serum copeptin was remarkably increased with COVID-19 severity with reasonable differentiation potential for recently admitted patients.

Nephrogenic diabetes insipidus: a comprehensive overview

Nephrogenic diabetes insipidus (NDI) is characterized by the inability to concentrate urine that results in polyuria and polydipsia, despite having normal or elevated plasma concentrations of arginine vasopressin (AVP). In this study, we review the clinical aspects and diagnosis of NDI, the various etiologies, current treatment options and potential future developments. NDI has different clinical manifestations and approaches according to the etiology. Hereditary forms of NDI are mainly caused by mutations in the genes that encode key proteins in the AVP signaling pathway, while acquired causes are normally associated with specific drug exposure, especially lithium, and hydroelectrolytic disorders. Clinical manifestations of the disease vary according to the degree of dehydration and hyperosmolality, being worse when renal water losses cannot be properly compensated by fluid intake. Regarding the diagnosis of NDI, it is important to consider the symptoms of the patient and the diagnostic tests, including the water deprivation test and the baseline plasma copeptin measurement, a stable surrogate biomarker of AVP release. Without proper treatment, patients may developcomplications leading to high morbidity and mortality, such as severe dehydration and hypernatremia. In that sense, the treatment of NDI consists in decreasing the urine output, while allowing appropriate fluid balance, normonatremia, and ensuring an acceptable quality of life. Therefore, therapeutic options include nonpharmacological interventions, including sufficient water intake and a low-sodium diet, and pharmacological treatment. The main medications used for NDI are thiazide diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), and amiloride, used isolated or in combination.

The usefulness of copeptin for the diagnosis of nephrogenic diabetes insipidus in infancy: a case report

OBJECTIVES

We report a case of an infant with nephrogenic diabetes insipidus (NDI) diagnosed by the measurement of serum copeptin. There is only one study that previously evaluated the use of copeptin measurement in a pediatric patient.

CASE PRESENTATION

We present a 10-month-old child with polyuria-polydipsia syndrome (PPS) and hypernatremia that could not support water restriction due to increased risk of dehydration and worsening of his condition. Therefore, plasma measurement of copeptin allowed the diagnosis of NDI.

CONCLUSIONS

The water deprivation test (WDT) is considered the gold standard for diagnosis in PPS. However, WDT has serious limitations regarding its interpretation. Furthermore, the WDT can cause dehydration and hypernatremia, especially in young children. Therefore, the measurement of plasma copeptin seems to be a promising method to perform an earlier, safer, and accurate investigation of PPS. Up to now, our study is the second to report the usefulness of copeptin in children.

Vasopressin-Dependent Disorders: What Is New in Children?

Arginine vasopressin (AVP)-mediated osmoregulatory disorders, such as diabetes insipidus (DI) and syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are common in the differential diagnosis for children with hypo- and hypernatremia and require timely recognition and treatment. DI is caused by a failure to concentrate urine secondary to impaired production of or response to AVP, resulting in hypernatremia. Newer methods of diagnosing DI include measuring copeptin levels; copeptin is AVP's chaperone protein and serves as a surrogate biomarker of AVP secretion. Intraoperative copeptin levels may also help predict the risk for developing DI after neurosurgical procedures. Copeptin levels hold diagnostic promise in other pediatric conditions, too. Recently, expanded genotype and phenotype correlations in inherited DI disorders have been described and may better predict the clinical course in affected children and infants. Similarly, newer formulations of synthetic AVP may improve pediatric DI treatment. In contrast to DI, SIADH, characterized by inappropriate AVP secretion, commonly leads to severe hyponatremia. Contemporary methods aid clinicians in distinguishing SIADH from other hyponatremic conditions, particularly cerebral salt wasting. Further research on the efficacy of therapies for pediatric SIADH is needed, although some adult treatments hold promise for pediatrics. Lastly, expansion of home point-of-care sodium testing may transform management of SIADH and DI in children. In this article, we review recent developments in the understanding of pathophysiology, diagnostic workup, and treatment of better outcomes and quality of life for children with these challenging disorders.

Copeptin is increased by nausea and vomiting during hypertonic saline infusion in healthy individuals

OBJECTIVE

Measurement of hypertonic saline-stimulated copeptin has recently been described for the differentiation of polyuria-polydipsia syndrome. This study aims to determine the copeptin response to intravenous 3% hypertonic saline, including evaluation of adverse effects, in a local cohort of healthy adults >18 years in Australia.

DESIGN

Prospective clinical study.

METHODS

Twenty healthy volunteers (10 males and 10 females) were recruited. Participants underwent infusion of 3% hypertonic saline via a previously described standardized protocol, until the plasma sodium was ≥150 mmol/L, with measurement of plasma copeptin.

RESULTS

Mean peak sodium was 152 mmol/L ± SD 1.4 with osmolality 315 mmol/kg ± SD 3.9. Median volume of hypertonic saline infused to reach target sodium ≥ 150 mmol/L was 1536 mL (IQR 1362, 1992). Mean rate of plasma sodium rise was 5.9 mmol/L/hour ± SD 1.5. Hypertonic saline-stimulated copeptin had non-parametrical distribution with median of 33.8 pmol/L (IQR 27.6, 63.6). Overall median symptom burden was 6/10 (range 3/10-9/10). Copeptin was significantly higher for those who experienced nausea and/or vomiting (n = 13) (median 39.0 pmol/L; IQR 32.5, 90), compared to those participants who did not experience either (median 20.0 pmol/L; IQR 13.0, 31.0) (P = 0.003). There were no serious adverse events.

CONCLUSION

Hypertonic saline-stimulated copeptin measurements were similar in our population compared with previously reported reference intervals in healthy volunteers. There is a wide range of stimulated copeptin measurements in the healthy population. Nausea and vomiting are common adverse effects which enhance the copeptin response.

Novel molecular markers of cardiovascular disease risk in type 2 diabetes mellitus

Diabetes represents the leading risk factor for the development of cardiovascular disease (CVD). Chronic hyperglycemia and/or acute post-prandial changes in blood glucose determine an increase in reactive oxygen species (ROS), which play a fundamental role in endothelial dysfunction and in the nuclear transport of pro-atherogenic transcription factors that activate the "inflammasome". In addition, the glycemic alteration favors the formation and stabilization of atherosclerotic plaque through the mechanism of non-enzymatic glycation of different molecules, with the establishment of the so-called "advanced glycosylation end products" (AGE). Laboratory information provided by the level of biomarkers could make a quantitative and qualitative contribution to the clinical process of screening, prediction, prevention, diagnosis, prognosis and monitoring of cardiovascular (CV) risk linked to diabetes. This review describes the importance of specific biomarkers, with particular focus on novel ones, for stratifying and management of diabetes CV risk.