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

Enhancing diagnostic tools for vasopressin deficiency: insights from a single-center cohort study

CONTEXT

A recent multicenter trial confirmed that hypertonic saline-stimulated copeptin is superior to the arginine stimulation test (AST) for diagnosing vasopressin deficiency (AVP-D). The latter, though less accurate, is cheaper, better tolerated, and easier to perform. We aimed to improve AST diagnostic accuracy by incorporating additional parameters alongside copeptin.

METHODS

We retrospectively analysed ASTs from patients evaluated for suspected AVP-D. Final diagnosis was defined based on clinical, biochemical, radiological and follow-up data. We evaluated the test diagnostic accuracy based on either literature reported or ROC-based thresholds of several variables even in combination.

RESULTS

Nineteen patients were included and 8 were diagnosed with AVP-D. Copeptin response to AST was flat in AVP-D compared to primary polydipsia (PP) but showed limited discriminatory power with the maximal accuracy for copeptin-based parameters reaching 73.7%. AVP-D patients had lower urinary osmolarity (UOsm) and higher plasma osmolarity and serum sodium (Na) at AST end. Na at AST end was the best predictor of AVP-D (≥ 141 mmol/L: sensitivity 87.5%, specificity 100%, accuracy 94.7%, AUC 0.989). A multistep approach initially assessing Na at AST end and, in dubious cases (140-142 mmol/l), also either copeptin peak (≤ 4.1 pmol/L), UOsm (≤ 428 mOsm/kg), or absent posterior pituitary hyperintense signal achieved 100% diagnostic accuracy. Logistic regression using Na at AST end values combined with any of these aforementioned additional variables also reached complete discrimination between AVP-D and PP.

DISCUSSION

Combining multiple parameters after AST improved diagnostic accuracy, even without measuring copeptin. Despite the study's retrospective design, small sample, and absence of hypertonic saline testing, findings support the potential utility of a multivariable approach to AST interpretation.

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.

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.

Paediatric perspectives in the diagnosis of polyuria-polydipsia syndrome

The elucidation of the underlying cause of polyuria-polydipsia syndrome (PPS) is a challenging-especially in the differentiation of partial defects of arginine vasopressin (AVP) secretion or action from primary polydipsia. The water deprivation test has been utilized for many decades, and its application in the paediatric population has been applied using parameters predominantly established in adult cohorts. In more recent times, the development of automated commercial assays for copeptin, a surrogate marker for AVP, has represented a significant advancement in the diagnostic approach to PPS. Measurement of copeptin concentrations has major advantages and has essentially superseded measurement of AVP in diagnostic protocols for PPS. Additionally, stimulated-copeptin protocols utilizing hypertonic saline infusion, arginine, and glucagon have been investigated, and are promising. However, further studies are required in the population-incorporating the differences in physiological regulation of water homeostasis, and safety requirements-before there is widespread adoption into clinical practice.

Comparison of central diabetes insipidus (antidiuretic hormone deficiency) and stalk effect in patients with adamantinomatous and papillary craniopharyngioma

Craniopharyngioma (CP), a rare benign intracranial tumor, is still a major clinical challenge. There are two major histologic phenotypes: papillary CP (PCP) and adamantinomatous CP (ACP). This research aimed to assess the occurrence of central diabetes insipidus (antidiuretic hormone deficiency), the level of prolactin, and the stalk effect between PCP and ACP subtypes prior to and after surgery. Clinical data of CP patients before and after surgical resection of the tumor were analyzed retrospectively. These patients were divided into PCP and ACP groups, in accordance with the pathologic classification. The data of prolactin level, 24-h urinary volume, urine specific gravity and electrolyte status before and after surgery were evaluated in these two CP subtypes. A total of 86 CP patients were included, among which 28 patients were PCP and 58 were ACP. Compared to those prior to surgery, 24-h urine volume, serum sodium and serum chlorine concentrations were obviously increased, while prolactin and urine specific gravity were remarkably decreased in all the CP patients after surgery. Compared to those before operation, prolactin level and urine specific gravity were decreased, and 24-h urine volume, serum sodium and serum chlorine were elevated after operation in ACP patients. Moreover, after surgery, 24-h urine volume in PCP patients was higher than that in ACP group. The central diabetes insipidus in patients with CP was aggravated after surgical resection, especially in ACP patients. Moreover, the central diabetes insipidus of PCP subtype was more serious than that of ACP subtype.

Arginine vasopressin: Critical regulator of circadian homeostasis

Circadian rhythms optimally regulate numerous physiological processes in an organism and synchronize them with the external environment. The suprachiasmatic nucleus (SCN), the center of the circadian clock in mammals, is composed of multiple cell types that form a network that provides the basis for the remarkable stability of the circadian clock. Among the neuropeptides expressed in the SCN, arginine vasopressin (AVP) has attracted much attention because of its deep involvement in the function of circadian rhythms, as elucidated in particular by studies using genetically engineered mice. This review briefly summarizes the current knowledge on the peptidergic distribution and topographic neuronal organization in the SCN, the molecular mechanisms of the clock genes, and the relationship between the SCN and peripheral clocks. With respect to the physiological roles of AVP and AVP-expressing neurons, in addition to a sex-dependent action of AVP in the SCN, studies using AVP receptor knockout mice and mice genetically manipulated to alter the clock properties of AVP neurons are summarized here, highlighting its importance in maintaining circadian homeostasis and its potential as a target for therapeutic interventions.

Diabetes insipidus: Vasopressin deficiency…

Diabetes insipidus is a disorder characterized by hypo-osmotic polyuria secondary to abnormal synthesis, regulation, or renal action of antidiuretic hormone. Recently, an expert group, with the support of patient associations, proposed that diabetes insipidus be renamed to avoid confusion with diabetes mellitus. The most common form of diabetes insipidus is secondary to a dysfunction of the neurohypophysis (central diabetes insipidus) and would be therefore named 'vasopressin deficiency'. The rarer form, which is linked to renal vasopressin resistance (nephrogenic diabetes insipidus), would then be named 'vasopressin resistance'. The etiology of diabetes insipidus is sometimes clear, in the case of a neurohypophyseal cause (tumoral or infiltrative damage) or a renal origin, but in some cases diabetes insipidus can be difficult to distinguish from primary polydipsia, which is characterized by consumption of excessive quantities of water without any abnormality in regulation or action of antidiuretic hormone. Apart from patients' medical history, physical examination, and imaging of the hypothalamic-pituitary region, functional tests such as water deprivation or stimulation of copeptin by hyperosmolarity (induced by infusion of hypertonic saline) can be proposed in order to distinguish between these different etiologies. The treatment of diabetes insipidus depends on the underlying etiology, and in the case of a central etiology, is based on the administration of desmopressin which improves patient symptoms but does not always result in an optimal quality of life. The cause of this altered quality of life may be oxytocin deficiency, oxytocin being also secreted from the neurohypophysis, though this has not been fully established. The possibility of a new test using stimulation of oxytocin to identify alterations in oxytocin synthesis is of interest and would allow confirmation of a deficiency in those patients presenting with diabetes insipidus linked to neurohypophyseal dysfunction.

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.