Copeptin and its role in the diagnosis of diabetes insipidus and the syndrome of inappropriate antidiuresis

Challenging case of hypernatraemia in infancy

A 1-month-old male infant presented unwell with a fever and shock. Blood tests showed hypernatraemia, hyperchloraemia and raised urea and creatinine. Initially, he was treated for dehydration secondary to sepsis. However, high urine output combined with low urine osmolality and high plasma osmolality was suggestive of a disorder of arginine vasopressin (AVP), previously called diabetes insipidus (DI). On further endocrine testing, thyroxine (T4) level was low with an inappropriately normal thyroid-stimulating hormone level with no other anterior pituitary hormone abnormalities, a normal MRI head and ophthalmological assessment. Desmopressin, a synthetic form of AVP, was commenced, however, there was an inadequate response despite dose escalation, leading to a diagnosis of AVP resistance (previously nephrogenic DI) rather than AVP deficiency (previously cranial DI). Copeptin, an AVP precursor peptide and surrogate marker, was significantly elevated. A renal tubulopathy genetic screen demonstrated a likely pathogenic hemizygous variant in the AVP receptor 2 gene, which has previously been associated with X-linked vasopressin resistance. This case demonstrates the challenge of differentiating between AVP deficiency and resistance in infancy and the value of copeptin and genetic testing in confirming diagnosis. We outline an approach to fluid management in AVP disorders.

Disease activity score is associated with vertebral fragility fractures in patients with rheumatoid arthritis: a cross-sectional multidisciplinary study

Rheumatoid Arthritis (RA) is associated with osteometabolic alterations. This study aims to estimate the prevalence of osteometabolic complications and to explore the potential association with disease parameters in patients with RA. This cross-sectional study enrolled consecutive patients with diagnosis of RA, admitted to Rheumatology Unit of our Hospital and referred to the Endocrinology Unit for the assessment of osteometabolic health. Anamnestic, anthropometric, biochemical and instrumental data were collected for each subject. The prevalence of osteometabolic alterations was 35% for sarcopenia, 41% for osteoporosis and 28% for vertebral fragility fractures in a population of 110 RA patients. At multivariable analysis, copeptin showed direct association (β-coeff 0.006; p = 0.015) with lower lumbar bone mineral density (BMD) values on dual-energy X-ray absorptiometry (DXA). Disease Activity Score for 28 joints with C-Reactive Protein (DAS28-CRP) (OR 1.632; p = 0.031) proved to be associated with vertebral fragility fractures, correcting for age, sex, body mass index (BMI) and disease parameters. Furthermore, DAS28-CRP (β-coeff 0.584; p = 0.001), steroid therapy (β-coeff 0.993; p = 0.013), and old age (β-coeff 0.040; p = 0.013) were directly associated with sarcopenia score (SARC-F), while male sex showed indirect association (β-coeff - 1.027; p = 0.036), correcting for autoantibody positivity and BMI. In the last model, copeptin resulted indirectly associated with fat mass index on DXA (β-coeff - 0.236, p = 0.049), using age and disease parameters, as covariates. RA is characterized by a high prevalence of osteometabolic complications, caused by a complex interplay between autoimmune and metabolic pathways. Management of osteometabolic health in RA patients should be a shared decision making between rheumatologist and endocrinologist.

A post-hoc internal validation of arginine-stimulated copeptin cut-offs for diagnosing AVP deficiency (central diabetes insipidus)

BACKGROUND

Distinguishing arginine vasopressin (AVP) deficiency (central diabetes insipidus) from primary polydipsia is challenging. While hypertonic saline-stimulated copeptin testing provides the highest diagnostic accuracy, it is often restricted to specialised centres, requiring close monitoring and potentially causing patient discomfort. Initially, arginine-stimulated copeptin was proposed as a simpler alternative, but a head-to-head comparison study found it less precise than hypertonic saline stimulation. However, the same study identified two new high sensitivity and specificity cut-offs for arginine-stimulated copeptin, though these cut-offs have yet to be validated.

METHODS

This is a secondary post-hoc analysis of the initial prospective multicentre study, including adult patients with confirmed AVP deficiency or primary polydipsia. Participants underwent the arginine stimulation test, with plasma copeptin measured at baseline and 60- and 90 min after arginine infusion. The primary objective was to revisit the original study to internally validate the proposed arginine-stimulated copeptin cut-offs of > 5.2pmol/L (high specificity cut-off with > 90% specificity for primary polydipsia) and ≤ 3.0 pmol/L (high specificity cut-off with > 90% specificity for AVP deficiency).

FINDINGS

In total, 96 patients were included between May 2013 and June 2018: n = 38 [40%] with AVP deficiency and n = 58 [60%] with primary polydipsia. At 60 min after arginine infusion, a copeptin level ≤ 3.0 pmol/L showed a specificity of 95% (95% CI: 0.88-1.00) for AVP deficiency, while a copeptin level > 5.2 pmol/L demonstrated a specificity of 97% (95% CI: 0.92-1.00) for primary polydipsia. The ≤ 3.0 pmol/L cut-off accurately identified 71% (n = 27/38) of patients with AVP deficiency, and the > 5.2 pmol/L cut-off correctly identified 69% (n = 40/58) of patients with primary polydipsia.

INTERPRETATION

This analysis validates two new copeptin cut-offs of the arginine stimulation test to distinguish AVP deficiency from primary polydipsia: >5.2 pmol/L for high specificity in diagnosing primary polydipsia and ≤ 3.0 pmol/L for high specificity in diagnosing AVP deficiency. These thresholds might offer a practical initial alternative to hypertonic saline testing.

REGISTRATION

Clinicaltrials.gov (NCT00757276).

Copeptin Hormone Concentrations in Dogs with Heart Disease and Relationship with Antidiuretic Hormone

Antidiuretic hormone (ADH) is upregulated in dogs with cardiac disease. However, measurement of ADH is impractical in a clinical setting. Copeptin is co-secreted with ADH, making it a potential biomarker of ADH secretion. We hypothesized that dogs with cardiac disease would upregulate copeptin concentrations and that copeptin would positively correlate with ADH, serum chloride ([Cl-]), and degree of mathematical [Cl-] correction. The study population comprised 19 healthy, 20 preclinical (Stage B), and 20 congestive heart failure (CHF, Stage C or D) dogs. Groups were compared with Kruskal-Wallis tests. The agreement between ADH and copeptin was assessed with Bland-Altman analysis. Relationships between copeptin and clinical variables were explored using multivariable linear regression. There were no significant differences in copeptin concentrations among healthy (median 54.9 pg/mL; range 0.5-196.1), preclinical (median 43.6 pg/mL; range 0.5-131.4), and CHF (median 60.5 pg/mL; range 0.5-997.8) dogs (p = 0.76). Relative to ADH, copeptin showed a negative proportional bias of -87.8 pg/mL with wide limits of agreement (-421.8 to 246.2). Linear regression showed a significant influence of age on copeptin concentration. Copeptin measured by ELISA does not reflect the ADH concentration in healthy dogs or in dogs with cardiac disease. Copeptin concentrations are, however, inversely associated with age.

Urinary oxytocin secretion after pituitary surgery, early arginine vasopressin deficiency and syndrome of inappropriate antidiuresis

PURPOSE

Transient arginine vasopressin deficiency (AVP-D), previously called diabetes insipidus, is a well-known complication of transsphenoidal pituitary surgery (TPS) with no definite predictive biomarker to date making it difficult to anticipate. While oxytocin (OXT) was previously suggested as a possible biomarker to predict syndrome of inappropriate diuresis (SIAD)-related hyponatraemia after TPS, its secretion in patients presenting with AVP-D remains poorly understood. We therefore hypothesized that OXT might present a different secretion in the case of AVP-D which would support its potential as an early biomarker of AVP-D. Moreover, we hypothesized that abnormal secretion of OXT might occur later on, notably with SIAD.

METHODS

We measured the urinary output of OXT in 67 consecutive patients subjected to TPS and compared the values of oxytocin between time-points and OXT ratio between groups. The primary endpoint of our study was to identify a difference in urinary OXT excretion in patients suffering from AVP-D compared to patients remaining normonatraemic. As a secondary endpoint, we compared the evolution of OXT secretion after the diagnosis of AVP-D in both groups, comparing the patients that later developed SIAD with the ones that did not.

RESULTS

Patients developing AVP-D showed a delay in the increase of OXT secretion after TPS as shown by a significantly lower ratio of OXT between the first postoperative day and the day of surgery (0.88 VS 1.68, p = 0.0162, IC:0.2979-0.2642) but a significantly higher ratio of OXT between the fourth and the first postoperative days (1.17 VS 0.53, p = 0.0006, IC:-2.109-0.6092). Moreover, normonatraemic patients that did not show normalization of OXT levels at day 4 after surgery tended to develop SIAD later on.

CONCLUSION

Taken together, these results show for the first time that OXT release might help predict AVP-D after TPS and differentiate it from other pathologies of water-sodium balance.

Copeptin as a diagnostic and prognostic biomarker in pediatric diseases

Arginine vasopressin (AVP) plays a main role in maintaining the homeostasis of fluid balance and vascular tone and in regulating the endocrine stress response in response to osmotic, hemodynamic and stress stimuli. However, the difficulty in measuring AVP limits its clinical application. Copeptin, the C-terminal part of the AVP precursor, is released in an equimolar concentration mode with AVP from the pituitary but is more stable and simple to measure. Therefore, copeptin has emerged as a promising surrogate marker of AVP with excellent potential for the diagnosis, differentiation and prognosis of various diseases in recent decades. However, its application requires further validation, especially in the pediatric population. This review focuses on the clinical value of copeptin in different pediatric diseases and the prospects for its application as a potential biomarker.

CANDID Study: Clinical and Molecular Characterization of Congenital Arginine Vasopressin-Resistance and the Use of a Novel Diagnostic Biomarker in Indian Children

OBJECTIVES

To present authors' experience with congenital arginine vasopressin resistance (AVP-R) in children up to 12-y-old at a tertiary care center in Northern India.

METHODS

An ambispective analysis was conducted, focusing on clinical, biochemical, genetic evaluations, treatments, renal and neurological outcomes.

RESULTS

Data from 11 patients (two females) were included, with an average delay of 18 mo between symptom onset and diagnosis. The majority of children presented with failure to thrive (90.9%), polyuria (90.9%), and hyperosmolality (63.6%) at the time of diagnosis. Nearly one-fourth of the cohort experienced acute kidney injury. Random copeptin levels (340.7 ± 59.56 pmol/L) were significantly higher than the diagnostic cutoff suggested in the literature, and molecular diagnosis confirmed AVPR2 mutations in 90% of the cases. The subjects were followed for a median of 2.1 y (range: 1-4.7 y). During this period, there was a median increase of + 0.79 in BMI/weight-for-height SDS and a 30.55% reduction in urine output. However, 63.63% of the children continued to experience failure to thrive. None of the subjects developed renal structural abnormalities or chronic kidney disease (CKD) ≥ stage 2 by the final follow-up. Neurological evaluation revealed attention deficit hyperactivity disorder and gross developmental delay in two children and one child respectively.

CONCLUSIONS

This study provides the first comprehensive analysis of congenital AVP-R in a low-middle-income setting.

Pathophysiology, symptoms, outcomes, and evaluation of hyponatremia: comprehension and best clinical practice

This review article series on water and electrolyte disorders is based on the 'Electrolyte Winter Seminar' held annually for young nephrologists in Japan. The seminar includes lively discussions based on cases, which are also partly included in this series as self-assessment questions. The first article in this series focuses on pathophysiology, symptoms, outcomes, and evaluation of hyponatremia, a common water and electrolyte disorder in clinical practice. Diagnosing the root cause(s) of hyponatremia can be challenging due to various etiologies and co-morbidities that affect water and electrolyte homeostasis, which can result in inappropriate management and worse outcomes in acute and chronic hyponatremia. This review provides an overview of pathophysiology, symptoms, outcomes, and evaluation of hyponatremia for better comprehension and improved clinical practice.

Diagnosis of arginine vasopressin deficiency in a patient with 10 years of polyuria and polydipsia following an Epstein-Barr virus infection

Polyuria-polydipsia syndrome is composed of arginine vasopressin deficiency, arginine vasopressin resistance and primary polydipsia and are characterised by severe polyuria with hypotonic urine. The water deprivation test is commonly used to indirectly assess the vasopressin response to water deprivation. We report a woman in her 20s who demonstrated severe polyuria (11-12 L/day) on submitting a 24-hour urine sample for analysis. She subsequently mentioned having had polyuria and polydipsia for 10 years after an Epstein-Barr virus infection. A water deprivation test with copeptin measurement confirmed arginine vasopressin deficiency. Treatment with desmopressin transformed her life. Further investigation revealed possible concurrent subclinical mixed connective tissue disease. We suspect Epstein-Barr virus infection to be the cause of the arginine vasopressin deficiency and possibly the trigger for the subclinical mixed connective tissue disease. This case also highlights the utility of copeptin measurements in differentiating the various polyuria-polydipsia syndromes.

Circadian copeptin and oxytocin profiles in anorexia nervosa: Exploring the interplay with neurohypophysis opioid tone

CONTEXT

Neurohypophysis (NH) function in eating disorders (ED) remains poorly elucidated. Studies on vasopressin and oxytocin display inconclusive findings regarding their levels and associations with psychological complications in ED. The profile of opioid tone, a crucial NH activity regulator, is also unknown.

OBJECTIVE

To characterise the circadian profile of NH hormones and NH opioid tone using positron emission tomography/MRI (PET/MRI) imaging in patients with ED compared to healthy controls.

METHODS

Twelve-point plasma circadian profiles of copeptin and oxytocin, alongside nutritional and psychological scores, were assessed in age-matched female participants: 13 patients with anorexia nervosa restrictive-type (ANR), 12 patients recovered from AN (ANrec), 14 patients with bulimia nervosa and 12 controls. Neurohypophysis PET/MRI [11C] diprenorphin binding potential (BPND) was evaluated in AN, ANrec and controls.

RESULTS

Results revealed lower copeptin circadian levels in both ANR and ANrec compared to controls, with no oxytocin differences. Bulimia nervosa exhibited elevated copeptin and low oxytocin levels. [11C] diprenorphin pituitary binding was fully localised in NH. Anorexia nervosa restrictive-type displayed lower NH [11C] diprenorphin BPND (indicating higher opioid tone) and volume than controls. In ANR, copeptin inversely correlated with osmolarity. Neurohypophysis [11C] diprenorphin BPND did not correlated with copeptin or oxytocin.

CONCLUSION

Copeptin demonstrated significant group differences, highlighting its potential diagnostic and prognostic value. Oxytocin levels exhibited conflicting results, questioning the reliability of peripheral blood assessment. Increased NH opioid tone in anorexia nervosa may influence the vasopressin or oxytocin release, suggesting potential therapeutic applications.

Idiopathic Arginine Vasopressin Deficiency With Mild and Reversible Hypercalcemia

Background

Arginine vasopressin deficiency (central diabetes insipidus) results from impaired hypothalamic-neurohypophyseal secretion of arginine vasopressin and leads to hypotonic polyuria and polydipsia. Common causes of arginine vasopressin deficiency include head trauma, pituitary surgery, neoplasms, and inflammatory stalk lesions; however, 25% to 50% of cases are idiopathic. Hypercalcemia can result in arginine vasopressin resistance (nephrogenic diabetes insipidus) and is an important differential in the evaluation of patients with hypotonic polyuria-polydipsia syndrome.

Case Report

A 32-year-old male presented with polyuria (24-hour urine output of 144 mL/kg), polydipsia (24-hour fluid intake of 130 mL/kg), and nocturia of 6 months' duration. Baseline investigations revealed normal liver, renal, serum potassium, and blood glucose levels. After overnight dehydration, serum osmolality increased to 317 mOsm/kg, while urine osmolality remained inappropriately low at 156 mOsm/kg. Mild hypercalcemia (serum calcium of 11.1 mg/dL) was noted. Upon arginine vasopressin challenge, urine osmolality increased by nearly 300%, suggesting complete arginine vasopressin deficiency. Evaluation for secondary causes was unremarkable. Magnetic resonance imaging of the pituitary revealed a normal anterior pituitary and pituitary stalk with an absent posterior pituitary bright spot. Idiopathic arginine vasopressin deficiency was diagnosed. The patient responded to oral desmopressin replacement, and normocalcemia was documented in multiple samples repeated when the patient was in a hydrated state.

Conclusion

Patients with arginine vasopressin deficiency can manifest concomitant mild and reversible dehydration-related hypercalcemia. A brisk increase in urine osmolality following subcutaneous arginine vasopressin injection and normal serum calcium levels after desmopressin therapy can establish that hypercalcemia is the effect and not the cause of the primary disorder.

Extreme hypernatremia after a laparoscopic hysterectomy and bilateral salpingo-oophorectomy: a case report and literature review

Congenital nephrogenic diabetes insipidus (NDI) primarily arises from an X-linked recessive inheritance caused by mutations in the AVPR2 gene, which is responsible for approximately 90% of cases. This condition has an incidence rate of 4-8 per million male live births, with females being much less frequently affected. Symptoms typically manifest shortly after birth, predominantly in males. The key clinical features of NDI include excessive urination (polyuria), compensatory excessive thirst (polydipsia), cognitive impairment, consistently low urine specific gravity, dehydration, and imbalances in electrolyte levels. This case study highlights an unusual occurrence of NDI in a 50-year-old Chinese woman attributed to a mutation in the AVPR2 gene. For more than a year, she had been suffering from excessive urination and severe thirst. The patient, who had undergone surgery for cervical cancer, developed polyuria and hypernatremia postoperatively. Initial laboratory analyses revealed normal blood sodium and chloride levels but reduced urine osmolality and specific gravity. Imaging assessments revealed no irregularities. To validate the diagnosis of NDI, she participated in a water deprivation and vasopressin test. Subsequent genetic tests revealed a thymine (T) to adenine (A) mutation, leading to a missense mutation in the AVPR2 gene. As part of her treatment, she was placed on a low-sodium diet and prescribed oral hydrochlorothiazide and indomethacin for 1 month, resulting in a marked improvement in her symptoms. To the best of our knowledge, this is the first documented case of NDI diagnosed postoperatively in an older female patient with AVPR2 heterozygosity. This case highlights an unusual instance of an X-linked recessive clinical presentation of NDI in an elderly female patient. This study also underscores the importance of conducting water deprivation, vasopressin tests, and genetic testing in establishing the underlying cause for individuals diagnosed with NDI.

Pituitary Disorders

In this article, we will review common pituitary disorders. There are 6 hormones secreted by the anterior pituitary gland: thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, growth hormone, and prolactin. The posterior pituitary gland stores and releases the hormones made in the hypothalamus, oxytocin and antidiuretic hormone, based on the body's needs. This article will discuss the role of these hormones, conditions and symptoms that occur with elevated or reduced hormone levels, as well as the evaluation and treatment of these pituitary disorders.

Role of Copeptin in Predicting Postoperative Hyponatremia and Hypernatremia in Patients Undergoing Endoscopic Pituitary Adenoma Surgery

BACKGROUND AND OBJECTIVES

Arginine vasopressin (AVP) is an important hormone responsible for maintaining sodium homeostasis after pituitary surgery. The measurement of AVP levels is difficult because of its short half-life (t 1/2 ). Copeptin is a preprohormone of AVP, and it is a more stable peptide, which can be used as surrogate marker for AVP. This study aims to assess the role of copeptin as a predictor of postoperative hyponatremia and hypernatremia in patients undergoing endoscopic pituitary adenoma surgery.

METHODS

This prospective study included 50 patients who underwent endoscopic pituitary adenoma surgery. Serum copeptin levels of these patients were assessed (1) preoperatively (C1), (2) at extubation (C2), and (3) postoperative day 4 (C3). Perioperative data regarding fluid and sodium balance were collected from patients. Statistical analysis was done using the above data.

RESULTS

The copeptin values were assessed against the sodium disturbances. 100% of patients who developed transient diabetes insipidus had a relative decrease in C2 from C1 ( P - .0002). 88% of patients who developed early hyponatremia had a relative increase in C2 as compared with C1 ( P < .01). 75% of patients who developed delayed hyponatremia had a relative increase in C3 as compared with C1 ( P = .003).

CONCLUSION

A relative increase or decrease in early change in copeptin (C2-C1) can predict development of early hyponatremia or transient central diabetes insipidus, respectively. A relative increase in delayed change in copeptin (C3-C1) can predict development of delayed hyponatremia.

Central Diabetes Insipidus in Children as a Diagnostic Challenge

Central diabetes insipidus (CDI) is a disorder in the pediatric population resulting from antidiuretic hormone deficiency. The excessive production of dilute urine characterizes it and manifests with polyuria, nocturia, and polydipsia. The diagnostics of CDI is often challenging, especially concerning the underlying condition of the disease. This article highlights the diverse clinical presentation of children with CDI and diagnostic difficulties among patients with polyuria and polydipsia. The article also reviews the etiology, symptoms, diagnostic workup, and management of CDI. We present 4 pediatric patients (aged 3-13.5 years) diagnosed with CDI of different etiology: 1 due to septo-optic dysplasia/optic nerve hypoplasia and 3 due to acquired processes such as Langerhans cell histiocytosis and germ cell tumor in 2 patients. Central diabetes insipidus was the first manifestation of a tumor or granuloma in all presented patients with acquired pathology. The patients sometimes need long-term follow-up to establish the proper final diagnosis.

Biomarkers That Seem to Have the Greatest Impact on Promoting the Formation of Atherosclerotic Plaque in Current Scientific Research

Atherosclerosis is a chronic inflammatory disease that causes degenerative and productive changes in the arteries. The resulting atherosclerotic plaques restrict the vessel lumen, causing blood flow disturbances. Plaques are formed mainly in large- and medium-sized arteries, usually at bends and forks where there is turbulence in blood flow. Depending on their location, they can lead to various disease states such as myocardial infarction, stroke, renal failure, peripheral vascular diseases, or sudden cardiac death. In this work, we reviewed the literature on the early detection of atherosclerosis markers in the application of photodynamic therapy to atherosclerosis-related diseases. Herein, we described the roles of C-reactive protein, insulin, osteopontin, osteoprotegerin, copeptin, the TGF-β cytokine family, and the amino acid homocysteine. Also, we discuss the role of microelements such as iron, copper, zinc, and Vitamin D in promoting the formation of atherosclerotic plaque. Dysregulation of the administered compounds is associated with an increased risk of atherosclerosis. Additionally, taking into account the pathophysiology of atherosclerotic plaque formation, we believe that maintaining homeostasis in the range of biomarkers mentioned in this article is crucial for slowing down the process of atherosclerotic plaque development and the stability of plaque that is already formed.

Association of Preoperative Copeptin Levels with Risk of All-Cause Mortality in a Prospective Cohort of Adult Cardiac Surgery Patients

We aimed to investigate the association of preoperative copeptin, a new cardiovascular biomarker, with short- and long-term mortality in a cohort of adult patients undergoing cardiac surgery, including its potential as a prognostic marker for clinical outcome. Preoperative blood samples of the Bern Perioperative Biobank, a prospective cohort of adults undergoing cardiac surgery during 2019, were analyzed. The primary and secondary outcome measures were 30-day and 1-year all-cause mortality. Optimal copeptin thresholds were calculated with the Youden Index. Associations of copeptin levels with the two outcomes were examined with multivariable logistic regression models; their discriminatory capacity was assessed with the area under the receiver operating characteristic (AUROC). A total of 519 patients (78.4% male, median age 67 y (IQR: 60-73 y)) were included, with a median preoperative copeptin level of 7.6 pmol/L (IQR: 4.7-13.2 pmol/L). We identified an optimal threshold of 15.9 pmol/l (95%-CI: 7.7 to 46.5 pmol/L) for 30-day mortality and 15.9 pmol/L (95%-CI: 9.0 to 21.3 pmol/L) for 1-year all-cause mortality. Regression models featured an AUROC of 0.79 (95%-CI: 0.56 to 0.95) for adjusted log-transformed preoperative copeptin for 30-day mortality and an AUROC of 0.76 (95%-CI: 0.64 to 0.88) for 1-year mortality. In patients undergoing cardiac surgery, the baseline levels of copeptin emerged as a strong marker for 1-year all-cause death. Preoperative copeptin levels might possibly identify patients at risk for a complicated, long-term postoperative course, and therefore requiring a more rigorous postoperative observation and follow-up.

Hyponatremia in the emergency department: an overview of diagnostic and therapeutic approach

INTRODUCTION

Hyponatremia, defined as a serum sodium concentration <135 mmol/l, is a frequent electrolyte disorder in patients presenting to an emergency department (ED). In this context, appropriate diagnostic and therapeutic management is rarely performed and challenging due to complex pathophysiologic mechanisms and a variety of underlying diseases.

OBJECTIVE

To implement a feasible pathway of central diagnostic and therapeutic steps in the setting of an ED.

METHODS

We conducted a narrative review of the literature, considering current practice guidelines on diagnosis and treatment of hyponatremia. Underlying pathophysiologic mechanisms and management of adverse treatment effects are outlined. We also report four cases observed in our ED.

RESULTS

Symptoms associated with hyponatremia may appear unspecific and range from mild cognitive deficits to seizures and coma. The severity of hyponatremia-induced neurological manifestation and the risk of poor outcome is mainly driven by the rapidity of serum sodium decrease. Therefore, emergency treatment of hyponatremia should be guided by symptom severity and the assumed onset of hyponatremia development, distinguishing acute (<48 hours) versus chronic hyponatremia (>48 hours).

CONCLUSIONS

Especially in moderately or severely symptomatic patients presenting to an ED, the application of a standard management approach appears to be critical to improve overall outcome. Furthermore, an adequate work-up in the ED enables further diagnostic and therapeutic evaluation during hospitalization.

Imaging and quantification of neuropeptides in mouse pituitary tissue by atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry

RATIONALE

Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) mass spectrometry has enabled the untargeted analysis and imaging of neuropeptides and proteins in biological tissues under ambient conditions. Sensitivity in AP-MALDI can be improved by using sample-specific preparation methods.

METHODS

A comprehensive and detailed optimization strategy including instrument parameters, matrix spraying and sample tissue washing pretreatment was implemented to enhance the sensitivity and coverage of neuropeptides in mouse pituitary tissues by commercial AP-MALDI mass spectrometry imaging (MSI).

RESULTS

The sensitivity of a commercial AP-MALDI system for endogenous neuropeptides in mouse pituitary was enhanced by up to 15.2-fold by shortening the transmission gap from the sample plate to the inlet, attaching copper adhesive tape to an indium tin oxide-coated glass slide, optimizing the matrix spray solvent and using sample tissue washing pretreatment. Following careful optimization, the distributions of nine endogenous neuropeptides were successfully visualized in the pituitary. Furthermore, the quantitative capability of AP-MALDI for neuropeptides was evaluated and the concentrations of neuropeptides oxytocin and vasopressin in the pituitary posterior lobe were increased approximately twofold under hypertonic saline stress.

CONCLUSION

Mouse pituitary neuropeptides have emerged as important signaling molecules due to their role in stress response. This work indicates the potential of modified AP-MALDI as a promising AP MSI method for in situ visualization and quantification of neuropeptides in complex biological tissues.

Chronic Hyponatremia: The Role of Reset Osmostat in Patients with Suspected SIAD

Background: Hyponatremia is common, particularly among the elderly. Reset osmostat (RO) serves as an alternative diagnosis to the syndrome of inappropriate antidiuresis (SIAD). There is limited information available regarding the prevalence of RO in outpatient clinics and hospital wards. The water-diluting test is considered the gold standard for the diagnosis of RO. The recent identification of copeptin provides an additional diagnostic marker alongside the utilization of fractional uric acid excretion. Methods: This single-center, prospective, observational study involved eight patients undergoing a water-diluting test over a study period of 2 years. Results: Reset osmostat was diagnosed in 50% of cases, while SIAD was confirmed in one patient. The tests were inconclusive for the remaining three patients. Conclusions: Our findings suggest that reset osmostat, despite its rarity, is a plausible diagnosis in chronic hyponatremia. The relevance of copeptin could not be confirmed in this study. Moreover, fractional uric acid excretion might be as effective as the water-diluting test in diagnosing reset osmostat.

Construction of a 3-year risk prediction model for developing diabetes in patients with pre-diabetes

Introduction

To analyze the influencing factors for progression from newly diagnosed prediabetes (PreDM) to diabetes within 3 years and establish a prediction model to assess the 3-year risk of developing diabetes in patients with PreDM.

Methods

Subjects who were diagnosed with new-onset PreDM at the Physical Examination Center of the First Affiliated Hospital of Soochow University from October 1, 2015 to May 31, 2023 and completed the 3-year follow-up were selected as the study population. Data on gender, age, body mass index (BMI), waist circumference, etc. were collected. After 3 years of follow-up, subjects were divided into a diabetes group and a non-diabetes group. Baseline data between the two groups were compared. A prediction model based on logistic regression was established with nomogram drawn. The calibration was also depicted.

Results

Comparison between diabetes group and non-diabetes group: Differences in 24 indicators including gender, age, history of hypertension, fatty liver, BMI, waist circumference, systolic blood pressure, diastolic blood pressure, fasting blood glucose, HbA1c, etc. were statistically significant between the two groups (P<0.05). Differences in smoking, creatinine and platelet count were not statistically significant between the two groups (P>0.05). Logistic regression analysis showed that ageing, elevated BMI, male gender, high fasting blood glucose, increased LDL-C, fatty liver, liver dysfunction were risk factors for progression from PreDM to diabetes within 3 years (P<0.05), while HDL-C was a protective factor (P<0.05). The derived formula was: In(p/1-p)=0.181×age (40-54 years old)/0.973×age (55-74 years old)/1.868×age (≥75 years old)-0.192×gender (male)+0.151×blood glucose-0.538×BMI (24-28)-0.538×BMI (≥28)-0.109×HDL-C+0.021×LDL-C+0.365×fatty liver (yes)+0.444×liver dysfunction (yes)-10.038. The AUC of the model for predicting progression from PreDM to diabetes within 3 years was 0.787, indicating good predictive ability of the model.

Conclusions

The risk prediction model for developing diabetes within 3 years in patients with PreDM constructed based on 8 influencing factors including age, BMI, gender, fasting blood glucose, LDL-C, HDL-C, fatty liver and liver dysfunction showed good discrimination and calibration.

Cannabinoid receptor type 1 activation causes a water diuresis by inducing an acute central diabetes insipidus in mice

Cannabis and synthetic cannabinoid consumption are increasing worldwide. Cannabis contains numerous phytocannabinoids that act on the G protein-coupled cannabinoid receptor type 1 (CB1R) and cannabinoid receptor type 2 expressed throughout the body, including the kidney. Essentially every organ, including the kidney, produces endocannabinoids, which are endogenous ligands to these receptors. Cannabinoids acutely increase urine output in rodents and humans, thus potentially influencing total body water and electrolyte homeostasis. As the kidney collecting duct (CD) regulates total body water, acid/base, and electrolyte balance through specific functions of principal cells (PCs) and intercalated cells (ICs), we examined the cell-specific immunolocalization of CB1R in the mouse CD. Antibodies against either the C-terminus or N-terminus of CB1R consistently labeled aquaporin 2 (AQP2)-negative cells in the cortical and medullary CD and thus presumably ICs. Given the well-established role of ICs in urinary acidification, we used a clearance approach in mice that were acid loaded with 280 mM NH4Cl for 7 days and nonacid-loaded mice treated with the cannabinoid receptor agonist WIN55,212-2 (WIN) or a vehicle control. Although WIN had no effect on urinary acidification, these WIN-treated mice had less apical + subapical AQP2 expression in PCs compared with controls and developed acute diabetes insipidus associated with the excretion of large volumes of dilute urine. Mice maximally concentrated their urine when WIN and 1-desamino-8-d-arginine vasopressin [desmopressin (DDAVP)] were coadministered, consistent with central rather than nephrogenic diabetes insipidus. Although ICs express CB1R, the physiological role of CB1R in this cell type remains to be determined.NEW & NOTEWORTHY The CB1R agonist WIN55,212-2 induces central diabetes insipidus in mice. This research integrates existing knowledge regarding the diuretic effects of cannabinoids and the influence of CB1R on vasopressin secretion while adding new mechanistic insights about total body water homeostasis. Our findings provide a deeper understanding about the potential clinical impact of cannabinoids on human physiology and may help identify targets for novel therapeutics to treat water and electrolyte disorders such as hyponatremia and volume overload.

Anterior and Posterior Pituitary Function in Patients with Sheehan Syndrome - Combining the use of Insulin Tolerance Test and Copeptin Assay

Introduction

Sheehan syndrome (SS) typically involves the loss of anterior pituitary cells and rarely affects the posterior pituitary. The water deprivation test (WDT) is the gold standard for diagnosing central diabetes insipidus (CDI), but it is cumbersome. Serum copeptin measurements are an alternative for CDI diagnosis. In this study, we measured hypoglycaemia-stimulated serum copeptin in SS patients to assess posterior pituitary function alongside anterior pituitary hormone levels.

Methods

This study recruited 43 patients with SS on stable hormonal replacement except for growth hormone (GH), 18 patients with CDI, and 19 body mass index (BMI) and parity-matched controls. All patients with SS and four patients with CDI underwent an insulin tolerance test (ITT), and hypoglycaemia-stimulated copeptin levels were measured at 0, 30, 45, and 90 minutes after insulin injection.

Results

The mean serum copeptin level among patients with SS (26.01 ± 12.41 pmol/L) was significantly lower than that in healthy controls (31.92 ± 7.85 pmol/L) and higher than that in patients with CDI (1.81 ± 0.14 pmol/L). Using pre-defined cut-offs for CDI, basal serum copeptin <2.69 pmol/L and stimulated levels <4.92 pmol/L for complete central DI, and basal copeptin levels >2.69 pmol/L and stimulated copeptin <4.92 pmol/L for partial central DI, 9.2% (n = 4) of patients with SS had CDI, of which half had complete CDI and half had partial CDI.

Conclusion

A significant number of patients with SS who are on hormone replacement therapy show involvement of the posterior pituitary, despite not displaying symptoms.

A Comprehensive Review of Empty Sella and Empty Sella Syndrome

OBJECTIVE

Incidental radiographic findings of an empty sella are prevalent in up to 35% of the general population. While empty sella was initially considered clinically insignificant, a subset of patients exhibits endocrine or neuro-ophthalmologic manifestations which are diagnostic of empty sella syndrome (ESS). Recent studies suggest that more patients are affected by ESS than previously recognized, necessitating a deeper understanding of this condition. This comprehensive review describes a practical approach to evaluating and managing ESS.

METHODS

Literature review was conducted on etiologies and risk factors associated with primary and secondary empty sella, the radiologic features that differentiate empty sella from other sellar lesions, and the role of clinical history and hormone testing in identifying patients with ESS, as well as treatment modalities.

RESULTS

Pituitary function testing for somatotroph, lactotroph, gonadotroph, corticotroph, and thyrotroph abnormalities is necessary when suspecting ESS. While an isolated empty sella finding does not require treatment, ESS may require pharmacologic or surgical interventions to address hormone deficits or intracranial hypertension. Targeted hormone replacement as directed by the endocrinologist should align with guidelines and patient-specific needs. Treatment may involve a multidisciplinary collaboration with neurology, neurosurgery, or ophthalmology to address patient symptoms.

CONCLUSION

This review underscores the evolving understanding of ESS, stressing the significance of accurate diagnosis and tailored management to mitigate potential neurologic and endocrine complications in affected individuals.

A Case of Hypernatremia in a Newly Diagnosed Patient With Acute Myeloid Leukemia: Lessons for Nephrologists

Arginine vasopressin deficiency (AVP-D), formerly known as central diabetes insipidus, is a disease characterized by polyuria, polydipsia, and hypernatremia. The concomitant diagnosis of acute myeloid leukemia (AML) is an underappreciated event that requires prompt recognition and treatment by practicing nephrologists and hematologists. This report highlights this importance by describing the case of a 39-year-old patient newly diagnosed with AML who developed severe hypernatremia. The role of diagnostic testing through desmopressin (DDAVP) challenge and copeptin testing to confirm the diagnosis of AVP-D in this context and the use of DDVAP for treatment are discussed. Practicing nephrologists and primary care providers taking care of patients with similar symptoms will benefit from understanding the pathophysiology of AVP-D, its relationship with AML, and the prognosis in this patient cohort.

Importance of Intraoperative Factors in Postoperative Arginine Vasopressin Deficiency After Pituitary Adenoma Surgery

OBJECTIVE

Pituitary adenoma (PA) is the most frequent tumor in the sellar region. Arginine vasopressin deficiency (AVP-D), formerly known as central diabetes insipidus, is a common complication after pituitary surgeries. In this study, we reviewed patients with PAs after endoscopic transsphenoidal surgery, evaluated the incidence of postoperative AVP-D, and determined associated risk factors.

METHODS

We retrospectively studied 520 patients who underwent endoscopic transsphenoidal surgery for PAs and evaluated perioperative risk factors and their associations with postoperative AVP-D. Patients who developed AVP-D were categorized in 3 groups: (1) early AVP-D, (2) transient AVP-D, and (3) permanent AVP-D.

RESULTS

Of the 520 patients, 24.8% experienced early AVP-D, and 1.9% (n = 10) had transient AVP-D. Permanent AVP-D was observed in only 6 patients (1.1%). Gross total resection, hormonal remission, pituitary stalk manipulation, and intraoperative cerebrospinal fluid leak were significantly associated with a higher incidence of AVP-D (P = .027, P = .002, P < .001 and P < .001, respectively). All patients who developed permanent AVP-D had somatotroph adenomas. AVP-D was not found to be related with tumor size. The length of hospital stay was prolonged by AVP-D on average by 1.5 days (P = .018).

CONCLUSION

The reported incidence of AVP-D has a considerably wide range. A consistent definition and grading for AVP-D will increase consistency and comparability among studies. Nonetheless, most patients experience AVP-D on a temporary basis, and only a few require long-term treatment. Cerebrospinal fluid leak, gross total resection, and hormonal remission were identified as risk factors for postoperative AVP-D. We believe that the intraoperative risk factors play the main role in postoperative AVP-D. The course of surgery and operative findings help us plan selective postoperative patient monitoring and care.

[Dysnatremias - concepts and clinical work-up]

Osmotic gradients over cell membranes lead to water movement into or out of cells. An intact osmoregulation prevents osmotic gradients, thereby protecting cells from swelling or shrinking. Na+ is the major cation in the extracellular fluid (ECF) and the major determinant of the osmolarity in the ECF, including plasma. Therefore, the plasma-Na+ concentration needs to be tightly regulated. An excess of electrolyte-free water decreases the concentration of osmolytes leading to hyponatremia. In contrast, a free water deficit increases the osmolyte concentration leading to hypernatremia. Pathophysiology-oriented approaches to dysnatremic patients help both clinicians and patients. Therapeutic interventions depend on the differentiation between acute and chronic, asymptomatic, and symptomatic dysnatremia, and on the patient's extracellular volume status. The therapeutic armamentarium for hyponatremia consists of water restriction, hypertonic infusions, urea, V2 receptor-blockers, and sodium-glucose cotransporter 2 (SGLT2) inhibitors. Patients with hypernatremia are treated with electrolyte-free water or hypotonic sodium-containing solutions depending on their volume status. Basic concepts in the management of dysnatremic patients are discussed.

[Consensus recommendations on the diagnosis and treatment of hyponatremia from the Austrian Society for Nephrology 2024]

Hyponatremia is a disorder of water homeostasis. Water balance is maintained by the collaboration of renal function and cerebral structures, which regulate thirst mechanisms and secretion of the antidiuretic hormone. Measurement of serum-osmolality, urine osmolality and urine-sodium concentration help to diagnose the different reasons for hyponatremia. Hyponatremia induces cerebral edema and might lead to severe neurological symptoms, which need acute therapy. Also, mild forms of hyponatremia should be treated causally, or at least symptomatically. An inadequate fast increase of the serum sodium level should be avoided, because it raises the risk of cerebral osmotic demyelination. Basic pathophysiological knowledge is necessary to identify the different reasons for hyponatremia which need different therapeutic procedures.

The laboratory investigation of diabetes insipidus: A review

Diabetes insipidus (DI) is a group of disorders that lead to inappropriate production of large volumes of dilute urine. The three main forms are central DI (CDI), nephrogenic DI (NDI) and primary polydipsia (PP). Differentiating CDI/NDI from PP is important as patients with true DI are at risk of severe dehydration without treatment. Biochemical testing is key in the diagnosis of DI. The indirect water deprivation test (WDT) is commonly used in the investigation of DI but has drawbacks including being cumbersome and sometimes producing equivocal results. Direct measurement of AVP has theoretical advantages but has generally only been used in specialist centres. Disadvantages include the requirement to measure AVP under hypertonic stimulation and pre-analytical/analytical challenges. Copeptin (CT-proAVP) is a proxy marker for AVP that is more stable, easier to measure and has been studied more widely in recent years. Historically, the evidence supporting the diagnostic performance of these tests has been relatively poor, being based on a few small, usually single-centre studies. However more recent, well-designed prospective studies are improving the evidence base for investigation of DI. These studies have focused on the utility of copeptin measurements during stimulation tests. There is evidence that measurement of copeptin under stimulation offers improved diagnostic performance compared to the WDT. There is currently a lack of systematic, evidence-based guidelines on the diagnosis of DI, but as the quality of the evidence defining the diagnostic performance of tests for DI continues to improve, a clearer consensus on the optimal approach should become achievable.

Severe hypernatremia during postoperative care in patients with craniopharyngioma

Purpose

We aimed to describe and predict the risk of severe hypernatremia after surgical resection of craniopharyngioma and to identify the association of water intake, urine output, and sodium level change in the patients.

Method

The outcome was postoperative severe hypernatremia. We identified risk factors associated with hypernatremia using multivariable regression. We trained machine learning models to predict the outcome. We compared serum sodium change, intravenous input, oral input, total input, urine output, and net fluid balance according to different nurse shifts.

Results

Among 234 included patients, 125 developed severe hypernatremia after surgery. The peak incidence occurred during day 0 and day 6 after surgery. The risk was increased in patients with gross total resection (odds ratio (OR) 2.41, P < 0.001), high Puget classification (OR 4.44, P = 0.026), preoperative adrenal insufficiency (OR 2.01, P = 0.040), and preoperative hypernatremia (OR 5.55, P < 0.001). The random forest algorithm had the highest area under the receiver operating characteristic curve (0.770, 95% CI, 0.727-0.813) in predicting the outcome and was validated in the prospective validation cohort. Overnight shifts were associated with the highest serum sodium increase (P = 0.010), less intravenous input (P < 0.001), and less desmopressin use (P < 0.001).

Conclusion

The overall incidence of severe hypernatremia after surgical resection of craniopharyngioma was significant, especially in patients with gross total resection, hypothalamus distortion, preoperative adrenal insufficiency, and preoperative severe hypernatremia. Less intravenous input and less desmopressin use were associated with serum sodium increases, especially during overnight shifts.

Neuroendocrine adaptations to starvation

Famine and starvation have punctuated the evolutionary past of the human species. As such, we have developed hormonal responses to undernutrition that minimize energy expenditure on processes that are not critical for the survival of the individual, such as reproduction. In this review, we discuss neuroendocrine adaptations to starvation including hypogonadotropic hypogonadism, growth hormone resistance, hypercortisolemia, and the downregulation of the hypothalamic-pituitary-thyroid axis. We review the time-course of these adaptations by describing studies involving the short-term fasting of healthy individuals as well as studies describing the hormonal changes in states of chronic undernutrition, using individuals with anorexia nervosa as a model of chronic starvation. Lastly, we review representative clinical effects of chronic undernutrition.

Copeptin analysis in endocrine disorders

Copeptin is cleaved from the same precursor as arginine vasopressin and is released in equimolar amounts with arginine vasopressin from the posterior pituitary in response to the same stimuli. Its level of stability in the blood, quick and simple analysis, and ease of automation make it much easier to analyze than arginine vasopressin, thereby offering a suitable alternative to measuring arginine vasopressin in endocrine disorders. Research has demonstrated the suitability of copeptin in adults for the differentiation of arginine vasopressin resistance and arginine vasopressin deficiency from primary polydipsia, in addition to the early identification of arginine vasopressin deficiency following pituitary surgery; however, further research is still required in the Syndrome of Inappropriate Antidiuretic Hormone (SIADH) and the pediatric population.

Novel Biomarkers and Their Role in the Diagnosis and Prognosis of Acute Coronary Syndrome

The burden of cardiovascular diseases and the critical role of acute coronary syndrome (ACS) in their progression underscore the need for effective diagnostic and prognostic tools. Biomarkers have emerged as crucial instruments for ACS diagnosis, risk stratification, and prognosis assessment. Among these, high-sensitivity troponin (hs-cTn) has revolutionized ACS diagnosis due to its superior sensitivity and negative predictive value. However, challenges regarding specificity, standardization, and interpretation persist. Beyond troponins, various biomarkers reflecting myocardial injury, neurohormonal activation, inflammation, thrombosis, and other pathways are being explored to refine ACS management. This review article comprehensively explores the landscape of clinically used biomarkers intricately involved in the pathophysiology, diagnosis, and prognosis of ACS (i.e., troponins, creatine kinase MB (CK-MB), B-type natriuretic peptides (BNP), copeptin, C-reactive protein (CRP), interleukin-6 (IL-6), d-dimers, fibrinogen), especially focusing on the prognostic role of natriuretic peptides and of inflammatory indices. Research data on novel biomarkers (i.e., endocan, galectin, soluble suppression of tumorigenicity (sST2), microRNAs (miRNAs), soluble oxidized low-density lipoprotein receptor-1 (sLOX-1), F2 isoprostanes, and growth differentiation factor 15 (GDF-15)) are further analyzed, aiming to shed light on the multiplicity of pathophysiologic mechanisms implicated in the evolution of ACS. By elucidating the complex interplay of these biomarkers in ACS pathophysiology, diagnosis, and outcomes, this review aims to enhance our understanding of the evolving trajectory and advancements in ACS management. However, further research is necessary to establish the clinical utility and integration of these biomarkers into routine practice to improve patient outcomes.

Syndrome of inappropriate secretion of anti-diuretic hormone due to hypothalamic hamartoma: use of tolvaptan

OBJECTIVES

Hypothalamic hamartoma (HH) typically presents with gonadotrophin-dependent precocious puberty and/or seizures. Other endocrine disturbances are rare. We describe an infant with syndrome of inappropriate secretion of anti-diuretic hormone (SIADH) and a HH.

CASE PRESENTATION

A 6-week-old infant presented with seizures and life-threatening hyponatremia. A HH was identified on magnetic resonance imaging. Clinical examination and biochemistry were consistent with SIADH, and serum copeptin was high during hyponatremia, further supporting this diagnosis. Tolvaptan was effective in normalizing plasma sodium and enabling liberalization of fluids to ensure sufficient nutritional intake and weight gain and manage hunger.

CONCLUSIONS

Hyponatremia due to SIADH is novel at presentation of a HH, and can be challenging to diagnose and manage. Successful management of hyponatremia in this case was achieved using tolvaptan.

Metabolic effects of vasopressin in pathophysiology of diabetic kidney disease

The diabetic kidney disease (DKD) is the major cause of the chronic kidney disease (CKD). Enhanced plasma vasopressin (VP) levels have been associated with the pathophysiology of DKD and CKD. Stimulation of VP release in DKD is caused by glucose-dependent reset of the osmostat leading to secondary pathophysiologic effects mediated by distinct VP receptor types. VP is a stress hormone exhibiting the antidiuretic action in the kidney along with broad adaptive effects in other organs. Excessive activation of the vasopressin type 2 (V2) receptor in the kidney leads to glomerular hyperfiltration and nephron loss, whereas stimulation of vasopressin V1a or V1b receptors in the liver, pancreas, and adrenal glands promotes catabolic metabolism for energy mobilization, enhancing glucose production and aggravating DKD. Increasing availability of selective VP receptor antagonists opens new therapeutic windows separating the renal and extra-renal VP effects for the concrete applications. Improved understanding of these paradigms is mandatory for further drug design and translational implementation. The present concise review focuses on metabolic effects of VP affecting DKD pathophysiology.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Relapsing Syndrome of Inappropriate Antidiuretic Hormone Production Responding to Tolvaptan Treatment in a Patient With a Micronodular Formation of the Posterior Pituitary Gland

The syndrome of inappropriate ADH-secretion (SIADH) is a common cause of low sodium levels with diverse aetiology. Here, we report a case of a 41 years old male patient diagnosed with SIADH and a good response to Tolvaptan therapy. Of interest, as a potential unique cause, magnetic resonance imaging revealed a micronodular structure in the posterior pituitary, while no other common cause of SIADH could be identified. Hence, to the best of our knowledge, this is the first case of a Tolvaptan-responsive SIADH associated with a pituitary micronodular structure.

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.

Osmoadaptive GLP-1R signalling in hypothalamic neurones inhibits antidiuretic hormone synthesis and release

OBJECTIVES

The excessive release of the antidiuretic hormone vasopressin is implicated in many diseases including cardiovascular disease, diabetes, obesity, and metabolic syndrome. Once thought to be elevated as a consequence of diseases, data now supports a more causative role. We have previously identified CREB3L1 as a transcription factor that co-ordinates vasopressin synthesis and release in the hypothalamus. The objective here was to identify mechanisms orchestrated by CREB3L1 that co-ordinate vasopressin release.

METHODS

We mined Creb3l1 knockdown SON RNA-seq data to identify downstream target genes. We proceeded to investigate the expression of these genes and associated pathways in the supraoptic nucleus of the hypothalamus in response to physiological and pharmacological stimulation. We used viruses to selectively knockdown gene expression in the supraoptic nucleus and assessed physiological and metabolic parameters. We adopted a phosphoproteomics strategy to investigate mechanisms that facilitate hormone release by the pituitary gland.

RESULTS

We discovered glucagon like peptide 1 receptor (Glp1r) as a downstream target gene and found increased expression in stimulated vasopressin neurones. Selective knockdown of supraoptic nucleus Glp1rs resulted in decreased food intake and body weight. Treatment with GLP-1R agonist liraglutide decreased vasopressin synthesis and release. Quantitative phosphoproteomics of the pituitary neurointermediate lobe revealed that liraglutide initiates hyperphosphorylation of presynapse active zone proteins that control vasopressin exocytosis.

CONCLUSION

In summary, we show that GLP-1R signalling inhibits the vasopressin system. Our data advises that hydration status may influence the pharmacodynamics of GLP-1R agonists so should be considered in current therapeutic strategies.

Idiopathic partial central diabetes insipidus

Diabetes insipidus is a rare disorder characterized by the inability to concentrate urine, which results in hypotonic urine and increased urinary volume. It may occur because of antidiuretic hormone deficiency or resistance to its action in the renal tubules. When there is a deficiency in the synthesis of antidiuretic hormones, diabetes insipidus is called central; when there is resistance to its action in the renal tubules, it is said to be nephrogenic. We report a case of idiopathic partial central diabetes insipidus and highlight the management and treatment of the disease.

Severe hyponatraemia with cerebral oedema after Pfizer BNT162b2 mRNA vaccination against COVID-19

Background

Severe hyponatraemia can lead to serious neurological complications including coma, seizure and death. Hyponatraemia and the Syndrome of Inappropriate Antidiuretic Hormone (SIADH) has been previously described in cases of COVID-19, however there have been few reports post vaccination. We describe a case of severe hyponatraemia post second Pfizer BNT162b2 mRNA vaccination against COVID-19.

Case presentation

A 48-year-old previously well woman presented to the emergency department with severe headaches and confusion one day after she received her second Pfizer COVID-19 vaccination. She reported no more than 2.5 L fluid intake. Vital signs were normal. Laboratory investigation revealed serum sodium 113 mmol/L, potassium 3.4 mmol/L, urea 3.5 mmol/L and serum osmolality 266 mmol/kg. TSH, random cortisol and C-reactive protein levels were normal. She was found to be in urinary retention and developed marked polyuria post in dwelling catheter insertion. Following this she underwent spontaneous and rapid correction of serum sodium without intervention. Retrospective analysis showed an inappropriately high copeptin of 4.4 pmol/L.

Conclusions

It is important to be cautioned and aware of hyponatraemia as an immediate side effect of COVID-19 vaccination. The exact mechanism is unknown and further research is required to understand the acute endocrine effects which may arise in response to COVID-19 vaccination.

New developments and concepts in the diagnosis and management of diabetes insipidus (AVP-deficiency and resistance)

Diabetes insipidus (DI) is a disorder characterised by the excretion of large amounts of hypotonic urine, with a prevalence of 1 per 25,000 population. Central DI (CDI), better now referred to as arginine vasopressin (AVP)-deficiency, is the most common form of DI resulting from deficiency of the hormone AVP from the pituitary. The less common nephrogenic DI (NDI) or AVP-resistance develops secondary to AVP resistance in the kidneys. The majority of causes of DI are acquired, with CDI developing when more than 80% of AVP-secreting neurons are damaged. Inherited/familial CDI causes account for approximately 1% of cases. Although the pathogenesis of NDI is unclear, more than 280 disease-causing mutations affecting the AVP2 protein or AVP V2 receptor, as well as in aquaporin 2 (AQP2), have been described. Although the cAMP/protein kinase A pathway remains the major regulatory pathway of AVP/AQP2 action, in vitro data have also revealed additional cAMP independent pathways of NDI pathogenesis. Diagnosing partial forms of DI, and distinguishing them from primary polydipsia, can be challenging, previously necessitating the use of the water deprivation test. However, measurements of circulating copeptin levels, especially after stimulation, are increasingly replacing the classical tests in clinical practice because of their ease of use and high sensitivity and specificity. The treatment of CDI relies on desmopressin administration, whereas NDI requires the management of any underlying diseases, removal of offending drugs and, in some cases, administration of diuretics. A better understanding of the pathophysiology of DI has led to novel evolving therapeutic agents that are under clinical trial.

Evaluation and management of hypernatremia in adults: clinical perspectives

Hypernatremia is an occasionally encountered electrolyte disorder, which may lead to fatal consequences under improper management. Hypernatremia is a disorder of the homeostatic status regarding body water and sodium contents. This imbalance is the basis for the diagnostic approach to hypernatremia. We summarize the eight diagnostic steps of the traditional approach and introduce new biomarkers: exclude pseudohypernatremia, confirm glucose-corrected sodium concentrations, determine the extracellular volume status, measure urine sodium levels, measure urine volume and osmolality, check ongoing urinary electrolyte free water clearance, determine arginine vasopressin/copeptin levels, and assess other electrolyte disorders. Moreover, we suggest six steps to manage hypernatremia by replacing water deficits, ongoing water losses, and insensible water losses: identify underlying causes, distinguish between acute and chronic hypernatremia, determine the amount and rate of water administration, select the type of replacement solution, adjust the treatment schedule, and consider additional therapy for diabetes insipidus. Physicians may apply some of these steps to all patients with hypernatremia, and can also adapt the regimens for specific causes or situations.

Norepinephrine innervation of the supraoptic nucleus contributes to increased copeptin and dilutional hyponatremia in male rats

Dilutional hyponatremia associated with liver cirrhosis is due to inappropriate release of arginine vasopressin (AVP). Elevated plasma AVP causes water retention resulting in a decrease in plasma osmolality. Cirrhosis, in this study caused by ligation of the common bile duct (BDL), leads to a decrease in central vascular blood volume and hypotension, stimuli for nonosmotic AVP release. The A1/A2 neurons stimulate the release of AVP from the supraoptic nucleus (SON) in response to nonosmotic stimuli. We hypothesize that the A1/A2 noradrenergic neurons support chronic release of AVP in cirrhosis leading to dilutional hyponatremia. Adult, male rats were anesthetized with 2-3% isoflurane (mixed with 95% O2/5% CO2) and injected in the SON with anti-dopamine β-hydroxylase (DBH) saporin (DSAP) or vehicle followed by either BDL or sham surgery. Plasma copeptin, osmolality, and hematocrit were measured. Brains were processed for ΔFosB, dopamine β-hydroxylase (DBH), and AVP immunohistochemistry. DSAP injection: 1) significantly reduced the number of DBH immunoreactive A1/A2 neurons (A1, P < 0.0001; A2, P = 0.0014), 2) significantly reduced the number of A1/A2 neurons immunoreactive to both DBH and ΔFosB positive neurons (A1, P = 0.0015; A2, P < 0.0001), 3) reduced the number of SON neurons immunoreactive to both AVP and ΔFosB (P < 0.0001), 4) prevented the increase in plasma copeptin observed in vehicle-injected BDL rats (P = 0.0011), and 5) normalized plasma osmolality and hematocrit (plasma osmolality, P = 0.0475; hematocrit, P = 0.0051) as compared with vehicle injection. Our data suggest that A1/A2 neurons contribute to increased plasma copeptin and hypoosmolality in male BDL rats.

Copeptin in Growth Hormone-Treated Patients

Growth hormone (GH) changes body composition, including increasing body water. GH is known to have an anti-natriuretic effect in the kidney, but little is known of its effect on arginine-vasopressin (AVP) release. We studied the effect of GH on AVP release by measurement of copeptin, a fragment from the same precursor protein, in GH-treated patients with GH deficiency. The study was designed as a retrospective cohort study of biobank samples from 34 patients substituted with GH between 1999 and 2004. Copeptin and insulin-like growth factor 1 (IGF-1) results were compared with previously obtained data. An increase in IGF-1 and copeptin was seen at 3 and 6 months’ treatment compared to baseline. Between the 3 and 6 months follow up, copeptin levels were stable. There was a difference in HbA1c between 3 and 6 months (p < 0.01) and between baseline and 6 months (p = 0.042), with higher levels at 6 months. In addition, LDL levels were lower at the 6 months follow up (p = 0.046). The waist circumference at 3 months was lower (p = 0.02). To conclude, three months of GH treatment increased the levels of copeptin and the increase remained at 6 months. This could be a compensatory mechanism balancing the anti-natriuretic effect of GH treatment seen in previous studies.

Approach to the Patient: Hyponatremia and the Syndrome of Inappropriate Antidiuresis (SIAD)

Hyponatremia is the most common electrolyte disturbance seen in clinical practice, affecting up to 30% of acute hospital admissions, and is associated with significant adverse clinical outcomes. Acute or severe symptomatic hyponatremia carries a high risk of neurological morbidity and mortality. In contrast, chronic hyponatremia is associated with significant morbidity including increased risk of falls, osteoporosis, fractures, gait instability, and cognitive decline; prolonged hospital admissions; and etiology-specific increase in mortality. In this Approach to the Patient, we review and compare the current recommendations, guidelines, and literature for diagnosis and treatment options for both acute and chronic hyponatremia, illustrated by 2 case studies. Particular focus is concentrated on the diagnosis and management of the syndrome of inappropriate antidiuresis. An understanding of the pathophysiology of hyponatremia, along with a synthesis of the duration of hyponatremia, biochemical severity, symptomatology, and blood volume status, forms the structure to guide the appropriate and timely management of hyponatremia. We present 2 illustrative cases that represent common presentations with hyponatremia and discuss the approach to management of these and other causes of hyponatremia.

Syndrome of inappropriate antidiuretic hormone secretion

Hyponatremia is the most frequent electrolytic disorder in hospitalized patients, and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), the most frequent cause of hiponatremia with clinically normal extracellular volume. It consists of a disorder of the regulation of body water that obeys to different causes, mainly cancer, pulmonary illnesses, disorders of the central nervous system and diverse drugs. As in any hiponatremia it a physiological knowledge of the regulation of body water and sodium is essential as well as the application of precise diagnostic criteria in order to manage the problem with an effective treatment. The available data until the moment show that the clinical diagnosis of SIADH made by professionals is mainly not supported on the established criteria drawn by experts and this lack of accuracy probably hits in the therapeutic result. The basis of the treatment of the SIADH is to correct its cause, water restriction, solutes (sodium chloride) and the use of vaptans in case of failure of the previous measures.