Vasopressin in chronic psychiatric patients with primary polydipsia

The many faces of oxytocin: implications for psychiatry

Oxytocin is known as the 'love hormone' due its role in promoting mother-child and pair bonding. More recent research indicates that oxytocin may have broader pro-social effects on behavior and cognition, which points towards oxytocin's potential as an agent to help improve social cognition and functioning in psychiatric disorders such as schizophrenia and autism. However, new research on oxytocin has also uncovered a 'darker side', including oxytocin's possible role in social out-grouping and envy. Instead of a simple view of oxytocin as 'good' or 'bad', a more accurate depiction of oxytocin's role in social processing likely involves the presence of moderating factors. We review moderation effects in oxytocin and their implications for psychiatry. One implication is that, across diagnostic categories, oxytocin administration may have positive effects for patients with social cognitive deficits but negative effects for patients with social cognitive bias. We conclude that future intervention studies should use methods such as signal detection to measure both deficit and bias parameters of social cognition and to evaluate potential individual and contextual moderators both within and between psychiatric diagnoses in order to determine for whom oxytocin treatment may be beneficial and for whom it may actually be harmful.

Brain circuit dysfunction in a distinct subset of chronic psychotic patients

OBJECTIVE

To identify the mechanism of unexplained hyponatremia and primary polydipsia in schizophrenia and its relationship to the underlying psychiatric illness.

METHODS

Briefly review previous studies that led to the conclusion the hyponatremia reflects altered hippocampal inhibition of peripheral neuroendocrine secretion. In greater detail, present the evidence supporting the hypothesis that circuit dysfunction associated with the hyponatremia and the polydipsia contributes to the underlying mental disorder.

RESULTS

Polydipsic patients with and without hyponatremia exhibit enhanced neuroendocrine responses to psychological stress in proportion to structural deformations on their anterior hippocampus, amygdala and anterior hypothalamus. Nonpolydipsic patients exhibit blunted responses and deformations on other hippocampal and amygdala surfaces. The deformations in polydipsic patients are also proportional to diminished peripheral oxytocin levels and impaired facial affect recognition that is reversed by intranasal oxytocin. The anterior hippocampus is at the hub of a circuit that modulates neuroendocrine and other responses to psychological stress and is implicated in schizophrenia. Preliminary data indicate that other measures of stress reactivity are also enhanced in polydipsics and that the functional connectivity of the hippocampus with the other structures in this circuitry differs in schizophrenia patients with and without polydipsia.

CONCLUSION

Polydipsia may identify a subset of schizophrenia patients whose enhanced stress reactivity contributes to their mental illness. Stress reactivity may be a symptom dimension of chronic psychosis that arises from circuit dysfunction that can be modeled in animals. Hence polydipsia could be a biomarker that helps to clarify the pathophysiology and heterogeneity of psychosis as well as identify novel therapies. Clinical investigators should consider obtaining indices of water balance, as these may help them unravel and more concisely interpret their findings. Basic researchers should assess if the polydipsic subset is a patient group particularly suitable to test hypotheses arising from their translational studies.

A systematic review of the ability of urine concentration to distinguish antipsychotic- from psychosis-induced hyponatremia

Life-threatening hyponatremia in psychotic patients is common and typically is attributable to either antipsychotic medication or to acute psychosis in those with the polydipsia-hyponatremia syndrome. The preferred treatment for one situation may worsen the hyponatremia if caused by the other situation. Hence it is critical to distinguish between these two possibilities. Case reports and series were identified through electronic databases. Fifty-four cases of hyponatremia without recognized causes in psychotic patients were divided into those with dilute (<plasma osmolality) or concentrated (>plasma osmolality) urine. The distribution of urine concentration and measures likely to be associated with psychotic illness and its treatment were compared in both groups. Naranjo׳s scale was utilized to determine the probability hyponatremia was drug-induced. Urine osmolality fit a bimodal distribution (intersection 219mOsm/kg) better than a unimodal distribution. 'Probable' drug-induced cases occurred 6.8 (95%CI=1.6-28.9) times more often in those with concentrated urine. Acute psychotic exacerbations occurred 4.5 (95%CI=0.4-54.1) times more often in those with dilute urine. These findings, as well as several other trends in the data, indicate that measures of urine concentration can help distinguish between antipsychotic-induced and psychosis-induced hyponatremia.

Effect of COMT Val108/158Met genotype on risk for polydipsia in chronic patients with schizophrenia

Polydipsia is a serious condition often seen among patients with schizophrenia (SCZ). The cause of polydipsia is unknown; hence, it is hard to treat or manage. Animal studies showed that the drinking behavior is regulated by central dopaminergic neurotransmission at the hypothalamus. Meanwhile, the existence of a genetic predisposition to polydipsia in patients with SCZ has been suggested. The purpose of this study was to assess whether a functional polymorphism, Val(108/158)Met in the gene for catechol-O-methyltransferase (COMT), is associated with susceptibility to polydipsia using a Japanese sample of SCZ. Our sample includes 330 chronic patients with SCZ (83 polydipsic patients and 247 non-polydipsic controls). The common COMT Val(108/158)Met polymorphism was genotyped, and the differences in genotype distribution and allele frequency between cases and controls were evaluated using the χ(2) test. A significant association between the COMT Val(108/158)Met polymorphism and polydipsia was found (genotype distribution: χ(2) = 13.0, df = 2, p = 0.001; allele frequency: χ(2) = 7.50, df = 1, p = 0.006). The high-COMT activity group (Val/Val) was more frequent among patients with polydipsia compared with the low-COMT activity group (Val/Met + Met/Met) [odds ratio (OR) = 2.46]. The association survived after controlling for other possible confounding factors, including gender, age, age of onset, current antipsychotic dose, and smoking status. Our results suggest that the COMT Val(108/158)Met genotype may confer susceptibility to polydipsia in SCZ. To our knowledge, this is the first association study between the COMT gene and polydipsia in SCZ. Further studies with larger sample sizes are warranted to confirm present findings.

Modulation of parvalbumin interneuron number by developmentally transient neocortical vasopressin receptor 1a (V1aR)

Arginine-vasopressin (AVP) and the vasopressin 1a receptor (V1aR) modulate social behavior and learning and memory in adult animals. Both functions depend upon the normal emergence of the balance of excitation and inhibition (E/I balance) in the neocortex. Here, we tested the hypothesis that V1aR signaling and E/I balance converge through the influence of the neuropeptide on interneuron number achieved in the neocortex. Postnatal mapping of forebrain V1aR binding in male and female mice revealed a transient expression of high levels of receptor in the neocortex and hippocampus in the second and third post-natal weeks. Receptor binding levels in these cortical structures fell dramatically in the adult, maintaining high levels of expression subcortically. Surprisingly, we observed sex differences in the number of calbindin interneurons, and a contribution of V1aR to the number of parvalbumin-immunoreactive neurons in the adult mouse neocortex. These data suggest that individual differences in developmentally transient V1aR signaling and even sex may alter the development of E/I balance in the neocortex, with long-lasting influence on information processing.

Tolvaptan: a new tool for the effective treatment of hyponatremia in psychotic disorders

IMPORTANCE OF THE FIELD

Hyponatremia (serum sodium concentration < 136 mEq/liter) is a common and potentially life-threatening medical comorbidity seen in patients with psychotic disorders. Tolvaptan, a selective antagonist of the V(2)-receptor, is FDA-approved for the treatment of clinically significant hypervolemic and euvolemic hyponatremia. This represents a major development in the care of psychotic individuals with hyponatremia.

AREAS COVERED IN THE REVIEW

This review provides an overview of the existing literature on prevalence rates and risk factors associated with hyponatremia in psychotic patients (1923 - present). Tolvaptan is discussed as a potential advance in the treatment of hyponatremia in patients with psychotic disorders, and preliminary data are reviewed.

WHAT THE READER WILL GAIN

The reader will gain an appreciation of the prevalence of hyponatremia among psychotic individuals, an understanding of the distinctions between acute and chronic hyponatremia in this population, and awareness that effective treatments are becoming available.

TAKE HOME MESSAGE

A modest literature exists regarding prevalence rates and risk factors associated with hyponatremia in psychotic populations. Hyponatremia is common and serious enough to merit clinical concern. Perhaps, now that tolvaptan has been FDA-approved, progress will accelerate and new insights will develop that begin to bring relief from this medical comorbidity among psychotic patients.

Type d syndrome of inappropriate antidiuretic hormone secretion in a schizophrenia patient with polydipsia

A 55-year-old man with schizophrenia developed water intoxication due to primary polydipsia. His manner of antidiuretic hormone secretion was investigated by water loading and infusion of hypertonic saline to clarify the form of the syndrome of inappropriate antidiuretic hormone secretion. The plasma antidiuretic hormone level, which may be involved in the occurrence of water intoxication, was consistently low in this patient, and linked to type D syndrome of inappropriate antidiuretic hormone secretion, designated “hypovasopressinemic antidiuresis”. Although this type is not common, it should be considered as a pathophysiology for water intoxication in schizophrenia patients.

Involvement of neuropeptide systems in schizophrenia: human studies

Neuropeptides are heterogeneously distributed throughout the digestive, circulatory, and nervous systems and serve as neurotransmitters, neuromodulators, and hormones. Neuropeptides are phylogenetically conserved and have been demonstrated to regulate numerous behaviors. They have been hypothesized to be pathologically involved in several psychiatric disorders, including schizophrenia. On the basis of preclinical data, numerous studies have sought to examine the role of neuropeptide systems in schizophrenia. This chapter reviews the clinical data, linking alterations in neuropeptide systems to the etiology, pathophysiology, and treatment of schizophrenia. Data for the following neuropeptide systems are included: arginine-vasopressin, cholecystokinin (CCK), corticotropin-releasing factor (CRF), interleukins, neuregulin 1 (NRG1), neurotensin (NT), neuropeptide Y (NPY), opioids, secretin, somatostatin, tachykinins, thyrotropin-releasing hormone (TRH), and vasoactive intestinal peptide (VIP). Data from cerebrospinal fluid (CSF), postmortem and genetic studies, as well as clinical trials are described. Despite the inherent difficulties associated with human studies (including small sample size, variable duration of illness, medication status, the presence of comorbid psychiatric disorders, and diagnostic heterogeneity), several findings are noteworthy. Postmortem studies support disease-related alterations in several neuropeptide systems in the frontal and temporal cortices. The strongest genetic evidence supporting a role for neuropeptides in schizophrenia are those studies linking polymorphisms in NRG1 and the CCKA receptor with schizophrenia. Finally, the only compounds that act directly on neuropeptide systems that have demonstrated therapeutic efficacy in schizophrenia are neurokinin receptor antagonists. Clearly, additional investigation into the role of neuropeptide systems in the etiology, pathophysiology, and treatment of schizophrenia is warranted.

Roles of arginine vasopressin and atrial natriuretic peptide in polydipsia-hyponatremia of schizophrenic patients

Respective contributions of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) to the urinary sodium concentration were evaluated in 23 naturalistic incidents of polydipsia-hyponatremia observed in 11 hospitalized schizophrenics (10 males and 1 female). The sodium concentration of the spontaneously excreted urine was examined before and after the forced water restriction. Before the water restriction, mean (+/-S.D.) plasma ANP was 52.8 +/- 33.9 pg/ml (range = 6.9-137). Plasma AVP levels were below 0.3 pg/ml in 15 episodes; relatively high levels (> or = 0.3) were noted in eight episodes. Means of urinary sodium concentration (mEq/l) were significantly higher in episodes with high AVP (> or = 0.3) alone (25.0 +/- 8.2, n=4), with high ANP (> 43) alone (21.3+/-7.4, n = 9), and with high AVP and ANP (26.8 +/- 6.4, n = 4) as compared to that of the low AVP (< 0.3) and ANP (< or = 43) group (13.5 +/- 3.7, n = 6). The data indicate that the elevated urinary sodium in polydipsic patients is possibly due to the AVP-induced antidiuresis and/or the ANP-induced natriuresis. In addition, we observed a close relationship between elevated plasma AVP and vomiting, suggesting that vomiting is one of the causal factors responsible for AVP elevations in this syndrome.

Cerebrospinal fluid angiotensin-converting enzyme (ACE) correlates with length of illness in schizophrenia

The aim of the study was to evaluate a possible progression with time of cerebrospinal fluid (CSF) angiotensin-converting enzyme (ACE) levels in treated schizophrenia patients. CSF ACE was determined in duplicate by a sensitive inhibitor-binding assay (IBA) from morning CSF samples of 56 acute and chronic in-patients with schizophrenic psychoses diagnosed according to DSM-IV. CSF ACE correlated significantly with length of schizophrenic psychosis (r=0.39, p=0.003). There was also a positive significant correlation between CSF ACE and duration of current psychotic episode (r=0.39, p=0.003) as well as duration of current hospitalization (r=0.66, p<0.001). These significances were maintained even when patients who were not treated with antipsychotics at the time of sampling were excluded. The correlations also remained significant when controlling for current neuroleptic dose in chlorpromazine equivalents. Serum ACE did not correlate with any clinical variable. No significant correlations between serum or CSF ACE and age, diagnostic subgroup, gender, serum ACE, CSF to serum albumin ratios, or neuroleptic dose in chlorpromazine equivalents were detected. The elevation of CSF ACE seemed to be confined to a subgroup of chronic patients with few positive symptoms. Elevated CSF ACE may reflect an increased solubilization of ACE from cell membranes in the central nervous system or constitute an increased expression of the ACE gene in response to some stimuli. This may be a function of treatment or a result of the deteriorating schizophrenic process.

A demographic study of polydipsia in an institution for the intellectually disabled

OBJECTIVE

To measure the prevalence of primary polydipsia in an Ontario institution for residents with developmental disabilities and to explore the associations of polydipsia with age, sex and level of mental retardation.

METHOD

All 798 residents were screened for polydipsia using a behavioural questionnaire completed by caregivers.

RESULTS

Thirty-three cases were detected: the prevalence among the mobile resident population (n = 660) was 5%. We found no association of polydipsia with age, sex, or level of mental retardation.

CONCLUSIONS

Physicians should be aware of polydipsia because it is common among residents with moderate, severe, and profound mental disability. Unless screened for specifically, polydipsia may go unrecognized and may place the residents with mental handicap at risk for serious acute and chronic complications.

Patients With Disordered Water Balance: Innovative Psychiatric Nursing Intervention Strategies

1. Patients with disordered water balance (DWB) have difficulty with fluid intake/output and osmoregulation. These difficulties are characterized by polydipsia, polyuria, significant variation in pattern of excretion, abnormal diurnal weight gain, and behavioral changes. 2. Therapeutic milieu-management strategies for patients experiencing acute and chronic phases of DWB are the cornerstone of long-term management of these patients. 3. Implementation of the intervention and milieu-management strategies described in this article resulted in a reduction of patients requiring acute medical treatment subsequent to an acute phase of DWB.

A "biofeedback" approach to the treatment of chronic polydipsia

A novel behavioral method is described for the treatment of psychogenic polydipsia in a patient suffering from chronic schizophrenia. The patient was given feedback on serum sodium concentration, likely physical consequences, and the value of reducing fluid intake. An ABAB single-case design was used, with changes in sodium concentration (charted by the patient during the treatment phases) as the dependent variable. The patient showed substantially increased sodium concentration, which was maintained despite the withdrawal of feedback. This behavioral method appears promising in settings where restriction of fluid intake is not practical or ethical.

Atrial natriuretic peptide and arginine vasopressin secretion in schizophrenic patients

Plasma levels of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) were measured in 15 patients with schizophrenic or schizoaffective disorders and 15 healthy volunteers during oral water loading at 20 ml/kg. In the patient group, plasma AVP was secreted even when plasma osmolality was below 270 mosmol/kg, although the sensitivity of AVP secretion response to osmolality was lower than in the controls. The ANP level was higher in the group of patients than in the controls. There was a negative correlation between plasma ANP and osmolality in the patients. We speculate that the volume expansion caused by inappropriate AVP secretion stimulated plasma ANP release and that the natriuresis resulting from the elevated plasma ANP level might contribute to hyponatremia.

Elevated angiotensin-converting enzyme (kininase II) in the cerebrospinal fluid of neuroleptic-treated schizophrenic patients

Disturbances of water homeostasis have frequently been reported in schizophrenia. Water homeostasis is regulated by arginine vasopressin (AVP), the renin-angiotensin system and natriuretic hormones. The aim of this study was to determine the activity of the central renin-angiotensin system in schizophrenia by measuring levels of angiotensin-converting enzyme (ACE) in the cerebrospinal fluid (CSF) and blood in 14 in-patients with schizophrenia on neuroleptic medication and in 9 healthy volunteers. The levels of CSF ACE were significantly higher in the schizophrenia group. There were no correlations between CSF ACE and gender, age, age at first episode, duration of illness, term of hospitalization or neuroleptic dosage. No correlations between CSF ACE and serum ACE were found in either group. The authors suggest an activated central renin-angiotensin system in schizophrenia at least during antipsychotic drug treatment, which may cause 'psychogenic' polydipsia in some patients. ACE and the brain renin-angiotensin system may also play a role in the regulation of neuron growth and differentiation in schizophrenia.

An epidemiological study on hyponatremia in psychiatric patients in mental hospitals in Nara Prefecture

Hyponatremia occurs often in mental illness. The frequency was not noticed because of the uncharacteristic symptoms of mild hyponatremia. Of the 1,114 psychiatric inpatients retrospectively surveyed, 10.5% had hyponatremia. Not only patients with schizophrenia, but also patients with other mental illness, especially with epilepsy, having hyponatremia were confirmed. An early onset, a long duration of psychiatric disorder and a prolonged admission were statistically significant factors. Nicotine abuse was not a significant factor. It was suggested that the pathogenesis of hyponatremia in psychiatric patients might be involved in a chronic course of psychiatric disorders and poor response to psychopharmacotherapy.

Drinking, thirst and water intoxication

Drinking is an activity determined partly by oropharyngeal stimulation and gastrointestinal sensations as well as biochemical changes, and thirst need not be involved. It is sometimes disturbed in mania or depression. Overdrinking (polydipsia) is common in long-stay in-patients, but only gives rise to water intoxication when there is a variable functional renal abnormality such as SIADH causing water retention. In contrast, in affective disorders, disturbance of sodium retention may be seen, possibly representing failure of nervous vascular control as part of the mental illness.