Changing the name of diabetes insipidus: a position statement of The Working Group for Renaming Diabetes Insipidus

"What's in a name? That which we call a rose/By any other name would smell as sweet." (Juliet, from Romeo and Juliet by William Shakespeare). Shakespeare's implication is that a name is nothing but a word and it therefore represents a convention with no intrinsic meaning. Whilst this may be relevant to romantic literature, disease names do have real meanings, and consequences, in medicine. Hence, there must be a very good rational for changing the name of a disease that has a centuries-old historical context. A working group of representatives from national and international endocrinology and pediatric endocrine societies now proposes changing the name of "diabetes insipidus" to "Arginine Vasopressin Deficiency (AVP-D)" for central etiologies, and "Arginine Vasopressin Resistance (AVP-R)" for nephrogenic etiologies. This editorial provides both the historical context and the rational for this proposed name change.

Changing the name of diabetes insipidus: a position statement of The Working Group for Renaming Diabetes Insipidus

'What's in a name? That which we call a rose/By any other name would smell as sweet.' (Juliet, from Romeo and Juliet by William Shakespeare). Shakespeare's implication is that a name is nothing but a word and it therefore represents a convention with no intrinsic meaning. Whilst this may be relevant to romantic literature, disease names do have real meanings, and consequences, in medicine. Hence, there must be a very good rationale for changing the name of a disease that has a centuries-old historical context. A working group of representatives from national and international endocrinology, nephrology and pediatric societies now proposes changing the name of 'diabetes insipidus' to 'arginine vasopressin deficiency (AVP-D)' for central etiologies and 'arginine vasopressin resistance (AVP-R)' for nephrogenic etiologies. This editorial provides both the historical context and the rationale for this proposed name change.

Changing the name of diabetes insipidus: a position statement of The Working Group for Renaming Diabetes Insipidus

'What's in a name? That which we call a rose/By any other name would smell as sweet' (Juliet, from Romeo and Juliet by William Shakespeare). Shakespeare's implication is that a name is nothing but a word, and it therefore represents a convention with no intrinsic meaning. While this may be relevant to romantic literature, disease names do have real meanings, and consequences, in medicine. Hence, there must be a very good rationale for changing the name of a disease that has a centuries-old historical context. A working group of representatives from national and international endocrinology, and pediatric endocrine societies now proposes changing the name of 'diabetes insipidus' to 'arginine vasopressin deficiency (AVP-D)' for central etiologies, and 'arginine vasopressin resistance (AVP-R)' for nephrogenic etiologies. This article provides both the historical context and the rationale for this proposed name change.

Lower Oxytocin Levels Are Associated with Lower Bone Mineral Density and Less Favorable Hip Geometry in Hypopituitary Men

INTRODUCTION

Hypopituitary patients are at risk for bone loss. Hypothalamic-posterior pituitary hormones oxytocin and vasopressin are anabolic and catabolic, respectively, to the skeleton. Patients with hypopituitarism may be at risk for oxytocin deficiency. Whether oxytocin and/or vasopressin contribute to impaired bone homeostasis in hypopituitarism is unknown.

OBJECTIVES

To determine the relationship between plasma oxytocin and vasopressin levels and bone characteristics (bone mineral density [BMD] and hip structural analysis [HSA]) in patients who have anterior pituitary deficiencies only (APD group) or with central diabetes insipidus (CDI group).

METHODS

This is a cross-sectional study. Subjects included 37 men (17 CDI and 20 APD), aged 20-60 years. Main outcome measures were fasting plasma oxytocin and vasopressin levels, and BMD and HSA using dual X-ray absorptiometry.

RESULTS

Mean BMD and HSA variables did not differ between the CDI and APD groups. Mean BMD Z-scores at most sites were lower in those participants who had fasting oxytocin levels below, rather than above, the median. There were positive associations between fasting oxytocin levels and (1) BMD Z-scores at the spine, femoral neck, total hip, and subtotal body and (2) favorable hip geometry and strength variables at the intertrochanteric region in CDI, but not APD, participants. No associations between vasopressin levels and bone variables were observed in the CDI or ADP groups.

CONCLUSIONS

This study provides evidence for a relationship between oxytocin levels and BMD and estimated hip geometry and strength in hypopituitarism with CDI. Future studies will be important to determine whether oxytocin could be used therapeutically to optimize bone health in patients with hypopituitarism.

Low Plasma Oxytocin Levels and Increased Psychopathology in Hypopituitary Men With Diabetes Insipidus

CONTEXT

Oxytocin (OT) and vasopressin share anatomical pathways of synthesis and secretion, and patients with central diabetes insipidus (CDI) presumably are at risk for OT deficiency. However, an OT-deficient state in hypopituitary patients has not been established.

OBJECTIVES

We hypothesized that men with CDI compared to patients with similar anterior pituitary deficiencies (APD) but no CDI and healthy controls (HC) of similar age and body mass index, would have lower plasma OT levels, associated with increased psychopathology.

DESIGN

Cross-sectional.

SETTING

Clinical research center.

PARTICIPANTS

Sixty-two men (20 CDI, 20 APD, 22 HC), age 18 to 60 years.

INTERVENTIONS

Frequent sampling of blood every 5 minutes for OT over 1 hour and validated questionnaires to assess psychopathology.

MAIN OUTCOMES

Pooled plasma OT levels; depressive, anxiety, and alexithymia symptoms; and quality of life.

RESULTS

The mean 1-hour pool of fasting OT levels was lower in CDI compared with APD and HC (P = 0.02 and P = 0.009, respectively), with no differences between APD and HC (P = 0.78). Symptoms of depression, anxiety, and alexithymia were more pronounced in CDI than in HC (P = 0.001, P = 0.004, and P = 0.02, respectively). Although CDI and APD reported worse physical health compared with HC (P = 0.001 and P = 0.005) with no differences between APD and CDI, only CDI reported worse mental health compared with HC (P = 0.009).

CONCLUSIONS

We have demonstrated low plasma OT levels and increased psychopathology in hypopituitary men with CDI, suggestive of a possible OT-deficient state. Larger studies of both sexes are required to confirm these findings and clinically characterize hypopituitary patients with OT deficiency.

MON-425 SIADH with Epistaxis: Rule out Esthesioneuroblastoma

Background: Esthesioneuroblastoma (ENB) is a rare cancer that arises from the olfactory epithelium. Paraneoplastic syndromes may develop from the tumor’s ectopic production of hormonally active substances such as adrenocorticotropic hormone (ACTH), parathyroid hormone-related peptide (PTHrP), and arginine vasopressin (AVP). Here we describe a case of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in a patient with ENB. Case Presentation: A 40-year-old male with a past history of acute lymphoblastic leukemia as a child presented to the ED after 4 wks of intermittent left-sided epistaxis and nasal obstruction. MRI showed an enhancing mass in the left upper nasal cavity with extension into the ethmoid and sphenoid sinuses. Initial labs revealed serum [Na⁺]=129 mmol/L and subsequent work-up was consistent with SIADH: plasma osmolality=281 mOsm/kg, urine osmolality=479 mOsm/kg, and urine [Na⁺]=46 mmol/L. A random serum cortisol was undetectable, raising concern of adrenal insufficiency (AI). An ACTH stimulation test showed a peak cortisol of 15.3 mcg/dL at 60 min; without other signs or symptoms of AI, we decided to monitor the patient off steroids. He was placed on a fluid restriction of 1.0 L/d with improvement of serum [Na⁺] into the normal range. A later repeat ACTH stimulation test revealed a peak cortisol of 19.1 mcg/dL at 60 min, and we determined that his undetectable serum cortisol was secondary to administration of high-dose dexamethasone prior to biopsy of the nasal mass. Biopsy of the mass revealed a malignancy that stained positive for synaptophysin, chromogranin, NSE, CD56, and MDM2 consistent with ENB. PET/CT revealed uptake in the primary tumor mass and bilateral cervical lymph nodes. The patient underwent tumor resection and bilateral neck dissection, followed by adjuvant radiation and chemotherapy for metastatic disease. Serum [Na⁺] levels normalized after resection of the ENB, and the patient remained eunatremic without fluid restriction throughout his treatment with radiation and chemotherapy. Conclusions: Nasopharyngeal carcinoma, including ENB, should be suspected in younger patients who present with SIADH, especially in the setting of epistaxis. Our patient was diagnosed soon after presentation via imaging of the sinuses. However, diagnosis may be delayed in patients who are otherwise asymptomatic. Other endocrinopathies such as AI should be ruled out as causes of hyponatremia, but in younger patients SIADH should be considered to be due to a tumor until proven otherwise. Head and neck tumors are the second most common tumors associated with SIADH after lung tumors. Fluid restriction is an appropriate initial treatment for patients with mild hyponatremia. As in our case, hyponatremia and SIADH usually resolve soon after tumor resection. Serum [Na⁺] should be monitored following tumor resection as a biomarker of possible recurrence of ENB.

Thiazide-Associated Hyponatremia, Report of the Hyponatremia Registry: An Observational Multicenter International Study

BACKGROUND

Hyponatremia is a frequent and potentially life-threatening adverse side effect of thiazide diuretics. This sub-analysis of the Hyponatremia Registry database focuses on current management practices of thiazide-associated hyponatremia (TAH) and compares differences between TAH and syndrome of inappropriate antidiuretic hormone secretion (SIADH).

METHODS

We analyzed 477 patients from 225 US and EU sites with euvolemic hyponatremia ([Na+] ≤130 mEq/L) who were receiving a thiazide diuretic. Of these, 118 met criteria for true thiazide-induced hyponatremia (TIH).

RESULTS

Thiazide was withdrawn immediately after hyponatremia was diagnosed only in 57% of TAH; in these patients, the median rate of [Na+] change (Δdaily[Na+]) was significantly higher than those with continued thiazide treatment (3.8 [interquartile range: 4.0] vs. 1.7 [3.8] mEq/L/day). The most frequently employed therapies were isotonic saline (29.6%), fluid restriction (19.9%), the combination of these two (8.2%), and hypertonic saline (5.2%). Hypertonic saline produced the greatest Δdaily[Na+] (8.0[6.4] mEq/L/day) followed by a combination of fluid restriction and normal saline (4.5 [3.8] mEq/L/day) and normal saline alone (3.6 [3.5] mEq/L/day). Fluid restriction was markedly less effective (2.7 [2.7] mEq/L/day). Overly rapid correction of hyponatremia occurred in 3.1% overall, but in up to 21.4% given hypertonic saline. Although there are highly significant differences in the biochemical profiles between TIH and SIADH, no predictive diagnostic test could be derived.

CONCLUSIONS

Despite its high incidence and potential risks, the management of TAH is often poor. Immediate withdrawal of the thiazide is crucial for treatment success. Hypertonic saline is most effective in correcting hyponatremia but associated with a high rate of overly rapid correction. We could not establish a diagnostic laboratory-based test to differentiate TIH from SIADH.

Euvolemic hyponatremia in cancer patients. Report of the Hyponatremia Registry: an observational multicenter international study

Purpose

Hyponatremia secondary to SIADH is frequent in cancer patients and potentially deleterious. The aim of this sub-analysis of the Hyponatremia Registry database is to analyze current diagnostic and therapeutic management practices in cancer patients with SIADH.

Methods

We analyzed 358 cancer patients who had serum sodium concentration ([Na⁺]) ≤ 130 mEq/L and a clinical diagnosis of SIADH from 225 sites in the USA and EU.

Results

Precise diagnostic testing was performed in only 46%. Almost 12% of all patients did not receive any hyponatremia treatment. The most frequent therapies were fluid restriction (20%), isotonic saline (14%), fluid restriction/isotonic saline (7%), tolvaptan (8%), and salt tablets (7%). Hypertonic saline was used in less than 3%. Tolvaptan produced the greatest median rate of [Na⁺] change (IQR) (3.0 (4.7) mEq/L/day), followed by hypertonic saline (2.0(7.0) mEq/L/day), and fluid restriction/isotonic saline (1.9(3.2) mEq/L/day). Both fluid restriction and isotonic saline monotherapies were significantly less effective (0.8(2.0) mEq/L/day and 1.3(3.0) mEq/L/day, respectively) and were associated with clinically relevant rates of treatment failure. Only 46% of patients were discharged with [Na⁺] ≥ 130 mEq/L. Overly rapid correction of hyponatremia occurred in 11.7%.

Conclusions

Although essential for successful hyponatremia management, appropriate diagnostic testing is not routinely performed in current practice. The most frequently employed monotherapies were often ineffective and sometimes even aggravated hyponatremia. Tolvaptan was used less often but showed significantly greater effectiveness. Despite clear evidence that hyponatremia is associated with poor outcome in oncology patients, most patients were discharged still hyponatremic. Further studies are needed to assess the beneficial impact of hyponatremia correction with effective therapies.

Electronic supplementary material

The online version of this article (doi:10.1007/s00520-017-3638-3) contains supplementary material, which is available to authorized users.

The effect of chronic mild hyponatremia on bone mineral loss evaluated by retrospective national Danish patient data

PURPOSE

To evaluate the effect of chronic mild hyponatremia ([Na+]=130-137mmol/L) on bone mineral content (BMC) and bone mineral density (BMD) loss through multiple, serial dual-energy X-ray absorptiometry (DXA) scans.

METHODS

Utilizing biochemical and DXA scan data from two Danish regions between 2004 and 2011, supplemented with national Danish patient diagnosis and prescription reimbursement databases, a retrospective cohort study was performed. All subjects with more than one DXA scan were included, then stratified into "normonatremia" ([Na(+)]=[137.00-147.00] mmol/L) and "mild hyponatremia" ([Na(+)]=[130.00-137.00[mmol/L) based on mean and confidence interval (CI) values calculated from all plasma sodium measurements between each subject's first and last DXA scan. Baseline, follow-up and delta values for hip and lumbar spine BMC and BMD were estimated between groups, then adjusted for comorbidity and medication use.

RESULTS

Hip and lumbar spine groups had 884 and 1069 patients with "normonatremia" versus 58 and 58 patients with "mild hyponatremia", respectively. Mild hyponatremia was associated with lower BMC and BMD in nearly all regions of the hip, and with worse losses in the trochanteric, femoral neck and total hip regions. Mild hyponatremia had limited effect on the lumbar spine.

CONCLUSIONS

Chronic mild hyponatremia seems to greatly affect bone in the hip, while the effect is limited in the lumbar spine. We suggest further retrospective study of patients with moderate (P-Na=120-130mmol/L) to severe hyponatremia (P-Na<120mmol/L) and prospective studies to further examine the association.

Administration of dehydroepiandrosterone (DHEA) enhances visual-spatial performance in postmenopausal women

The current article examines the effect of administering dehydroepiandrosterone (DHEA) on visual-spatial performance in postmenopausal women (N = 24, ages 55-80). The concurrent reduction of serum DHEA levels and visual-spatial performance in this population, coupled with the documented effects of DHEA's androgenic metabolites on visual-spatial performance, suggests that DHEA administration may enhance visual-spatial performance. The current experiment used a double-blind, placebo-controlled crossover design in which 50 mg of oral DHEA was administered daily in the drug condition to explore this hypothesis. Performance on the Mental Rotation, Subject-Ordered Pointing, Fragmented Picture Identification, Perceptual Identification, Same-Different Judgment, and Visual Search tasks and serum levels of DHEA, DHEAS, testosterone, estrone, and cortisol were measured in the DHEA and placebo conditions. In contrast to prior experiments using the current methodology that did not demonstrate effects of DHEA administration on episodic and short-term memory tasks, the current experiment demonstrated large beneficial effects of DHEA administration on Mental Rotation, Subject-Ordered Pointing, Fragmented Picture Identification, Perceptual Identification, and Same-Different Judgment. Moreover, DHEA administration enhanced serum levels of DHEA, DHEAS, testosterone, and estrone, and regression analyses demonstrated that levels of DHEA and its metabolites were positively related to cognitive performance on the visual-spatial tasks in the DHEA condition.

Preparedness of the CTSA's structural and scientific assets to support the mission of the National Center for Advancing Translational Sciences (NCATS)

The formation of the National Center for Advancing Translational Sciences (NCATS) brings new promise for moving basic science discoveries to clinical practice, ultimately improving the health of the nation. The Clinical and Translational Science Award (CTSA) sites, now housed with NCATS, are organized and prepared to support in this endeavor. The CTSAs provide a foundation for capitalizing on such promise through provision of a disease-agnostic infrastructure devoted to clinical and translational (C&T) science, maintenance of training programs designed for C&T investigators of the future, by incentivizing institutional reorganization and by cultivating institutional support.

micro-Opioid receptor stimulation in the medial subnucleus of the tractus solitarius inhibits gastric tone and motility by reducing local GABA activity

We examined the effects of altering mu-opioid receptor (MOR) activity in the medial subnucleus of the tractus solitarius (mNTS) on several gastric end points including intragastric pressure (IGP), fundus tone, and the receptive relaxation reflex (RRR). Microinjection of the MOR agonist [d-Ala(2),MePhe(4),Gly(ol)(5)]enkephalin (DAMGO; 1-10 fmol) into the mNTS produced dose-dependent decreases in IGP. Microinjection of the endogenous MOR agonists endomorphin-1 and endomorphin-2 (20 fmol) into the mNTS mimicked the effects of 10 fmol DAMGO. Microinjection of 1 and 100 pmol DAMGO into the mNTS produced a triphasic response consisting of an initial decrease, a transient increase, and a persistent decrease in IGP. The increase in IGP appeared to be due to diffusion to the dorsal motor nucleus of the vagus. The effects of 10 fmol DAMGO in the mNTS were blocked by vagotomy and by blockade of MORs, GABA(A) receptors, and ionotropic glutamate receptors in the mNTS. The RRR response was abolished by bilateral microinjection of the opioid receptor antagonist naltrexone into the mNTS and reduced by intravenous administration of naltrexone. Our data demonstrate that 1) activation of MORs in the mNTS with femtomole doses of agonist inhibits gastric motility, 2) the mechanism of MOR effects in the mNTS is through suppression of local GABA activity, and 3) blockade of MORs in the mNTS prevents the RRR response. These data suggest that opioids play an important role in mediating a vagovagal reflex through release of an endogenous opioid in the mNTS, which, in turn, inhibits ongoing local GABA activity and allows vagal sensory input to excite second-order mNTS neurons.

GABA signaling in the nucleus tractus solitarius sets the level of activity in dorsal motor nucleus of the vagus cholinergic neurons in the vagovagal circuit

It has been proposed that there is an "apparent monosynaptic" connection between gastric vagal afferent nerve terminals and inhibitory projection neurons in the nucleus tractus solitarius (NTS) and that two efferent parallel pathways from the dorsal motor nucleus of the vagus (DMV) influence peripheral organs associated with these reflexes (6). The purpose of our study was to verify the validity of these views as they relate to basal control of gastric motility. To test the validity of a direct connection of vagal afferent terminals (known to release l-glutamate) directly impacting second-order projection neurons, we evaluated the effect of GABA(A) receptor blockade in the area of the medial subnucleus of the tractus solitarius (mNTS) on gastric motility. Microinjection of bicuculline methiodide into the mNTS produced robust decreases in gastric motility (-1.6 +/- 0.2 mmHg, P < 0.05, n = 23), which were prevented by cervical vagotomy and by pretreatment with kynurenic acid microinjected into the mNTS. Kynurenic acid per se had no effect on gastric motility. However, after GABA(A) receptor blockade in the mNTS, kynurenic acid produced a robust increase in gastric motility. To test for the contribution of two parallel efferent DMV pathways, we assessed the effect of either intravenous atropine methylbromide or N(G)-nitro-l-arginine methyl ester on baseline motility and on decreases in gastric motility induced by GABA(A) receptor blockade in the mNTS. Only atropine methylbromide altered baseline motility and prevented the effects of GABA(A) receptor blockade on gastric motility. Our data demonstrate the presence of intra-NTS GABAergic signaling between the vagal afferent nerve terminals and inhibitory projection neurons in the NTS and that the cholinergic-cholinergic excitatory pathway comprises the functionally relevant efferent arm of the vagovagal circuit.

Differential kinetics of oxytocin and vasopressin heteronuclear RNA expression in the rat supraoptic nucleus in response to chronic salt loading in vivo

Previous studies have shown that the secretion of oxytocin and vasopressin from the posterior pituitary always accompanies systemic hyperosmotic stimuli in rats, and that oxytocin and vasopressin mRNAs consistently increase in response to prolonged hyperosmotic stimuli. Hence, it has been widely interpreted that oxytocin and vasopressin secretion and gene expression are closely coupled. In the present study, we used both vasopressin and oxytocin intron- specific probes to measure vasopressin and oxytocin heteronuclear RNA (hnRNA) levels, respectively, by in situ hybridisation in the rat supraoptic nucleus (SON) in conjunction with radioimmunoassays of vasopressin and oxytocin peptide levels in plasma and in the posterior pituitary in normally hydrated rats and after 1-5 days of salt loading. Increased oxytocin secretion in response to hyperosmotic stimuli exceeded vasopressin secretion at every time point studied. Vasopressin hnRNA in the SON increased to near maximal levels within minutes after the hyperosmotic stimulus, and was maintained throughout all 5 days of salt loading. By contrast, oxytocin hnRNA did not significantly change from control levels until approximately 2 days after hyperosmotic stimulation, and was not maximal until 3 days. In summary, increases in oxytocin gene transcription in response to osmotic stimuli are dramatically delayed compared to increases in vasopressin gene transcription under the same conditions. These data indicate that oxytocin gene transcription is not as closely correlated with pituitary peptide secretion as is vasopressin gene transcription, and suggests that there is a fundamental difference in excitation-secretion-transcription coupling mechanisms that regulate these two closely related genes in the rat magnocellular neurones in the SON.

Microarray analysis of gene expression in the supraoptic nucleus of normoosmotic and hypoosmotic rats

1. Hypoosmolality produces a dramatic inhibition of vasopressin (VP) and oxytocin (OT) gene expression in the supraoptic nucleus (SON). This study examines the effect of sustained hypoosmolality on global gene expression in the OT and VP magnocellular neurons (MCNs) of the hypothalamo-neurohypophysial system (HNS), in order to detect novel genes in this system that might be involved in osmoregulation in the MCNs. 2. For this purpose, we used Affymetrix oligonucleotide arrays to analyze the expression of specific genes in laser microdissected rat SONs, and their changes in expression during chronic hypoosmolality. We identified over 40 genes that had three-fold or more greater expression in the SON versus total hypothalamus, and that also changed more than two fold in expression as a result of the chronic hypoosmolar treatment. These genes contained both novel as well as genes previously known to be present in the SON. All of the raw data for the genes that are expressed in the SON and altered by hypoosmolality can be found on the following NINDS website URL address: http://data.ninds.nih.gov/Gainer/Publications.

Cytochrome P-450-dependent metabolism of arachidonic acid in the kidney of rats with diabetes insipidus

This study compared the renal metabolism of arachidonic acid in Brattleboro (BB) (vasopressin deficient) and Long-Evans (LE) control rats and the effects of a cytochrome P-450 (CYP) inhibitor 1-aminobenzotriazole (ABT) on renal function in these animals. The production of 20-hydroxyeicosatetraenoic acid (20-HETE) by renal cortical and outer medullary microsomes was significantly greater in BB than in LE rats (155 +/- 16 vs. 92 +/- 13 and 59 +/- 7 vs. 33 +/- 3 pmol.min(-1).mg protein(-1)). Renal cortical epoxygenase activity was not different in these strains. The expression of CYP4A proteins was 58 and 78% higher in the renal cortex and outer medulla of BB than in LE rats. Chronic treatment of BB rats with a vasopressin type 2 receptor agonist for 1 wk normalized the renal production of 20-HETE. Chronic blockade of the formation of 20-HETE and EETs with ABT had little effect on renal function in LE rats. However, urine flow increased by 54% and urine osmolarity decreased by 33% in BB rats treated with ABT. Plasma levels of oxytocin fell significantly from 7.2 +/- 1.3 to 3.9 +/- 1.0 pg/ml. The effects of ABT in BB rats were attenuated by chronic infusion of oxytocin (0.7 ng.min(-1).100 g(-1)) to maintain fixed high plasma levels of this hormone. These results indicate that the expression of CYP4A protein and the renal formation of 20-HETE are elevated in the kidney of BB rats due to a lack of vasopressin and that chronic blockade of the formation of 20-HETE and EETs with ABT promotes water excretion in vasopressin-deficient BB rats by reducing the circulating levels of oxytocin, which is a weak vasopressin agonist.

Presumed infundibuloneurohypophysitis: unusual presentation in a postpartum patient

We describe a case of presumed postpartum infundibuloneurohypophysitis, which is a rare inflammatory process involving the pituitary stalk and posterior pituitary. Only one case has been previously reported in a postpartum woman. Serial MR images obtained in our patient revealed spontaneous regression of inflammation. The critical position of the inflammation leads to hormonal deficiencies, mostly involving the posterior pituitary. Treatment options include hormone replacement; the role of pharmacological steroids is controversial.

Acute endotoxemia in rats induces down-regulation of V2 vasopressin receptors and aquaporin-2 content in the kidney medulla

BACKGROUND

Endotoxemia can lead to fluid metabolism alterations despite unchanged or elevated plasma vasopressin (VP) levels, suggesting a refractoriness of the kidney to the effect of the peptide. To test this hypothesis, we examined the effect of lipopolysaccharide (LPS) injection on the expression of V2 receptors and aquaporin-2 in the kidney.

METHODS

Plasma VP and urine osmolality, and binding of [3H]VP to kidney membranes, Western blot, and immunohistochemical analysis of aquaporin-2, in situ hybridization for V2 VP receptors and cytokines mRNAs were measured in the kidney 3 to 24 hours after LPS injection, 250 microg/100 g, intraperitoneally.

RESULTS

LPS injection caused prolonged decreases in urine osmolality (up to 24 hours) without significant changes in plasma levels of sodium or VP. This was associated with marked decreases in V2 VP receptor mRNA and VP receptor number in the kidney, which were evident for up to 12 hours after LPS injection. Aquaporin-2 in kidney inner medulla was also reduced by about 50%. LPS induced interleukin (IL)-1beta in the kidney medulla by 3 hours, reached maximum at 6 hours, and started to decline by 12 hours, while it increased IL-6 mRNA significantly only at 3 hours. Interleukin mRNA expression was absent in kidneys of control rats. In vitro incubation of kidney medulla slices with IL-1beta reduced VP binding.

CONCLUSION

The inflammatory response to acute endotoxemia down regulates V2 VP receptors and aquaporin-2 of the kidney inner medulla resulting in prolonged impairment of the renal capacity to concentrate urine.

The effect of the maze procedure on the secretion of arginine-vasopressin and aldosterone

BACKGROUND

Excessive fluid retention is a serious complication after the maze procedure that cannot be totally explained by changes in levels of atrial natriuretic peptide. We therefore measured circulating levels of arginine vasopressin and aldosterone in patients undergoing the maze procedure to study their possible role in this postoperative complication.

METHODS

Serial arginine vasopressin and aldosterone levels were monitored for 72 hours in 11 patients after coronary artery bypass grafting and in 13 patients after the maze procedure. Hemodynamic data, urine output, fluid balance, and complications were recorded prospectively during the same period of time.

RESULTS

Plasma levels of arginine vasopressin and aldosterone were significantly higher in patients after the maze procedure when compared with patients after coronary artery bypass grafting.

CONCLUSIONS

This study documents that the maze procedure results in increased plasma arginine vasopressin and aldosterone levels and indicates that they, rather than atrial natriuretic peptide alone, participate in the excessive postoperative fluid retention that follows the maze procedure. We believe that these hormone elevations are most likely secondary to a temporary lack of response of the atrial baroreceptors. These results may explain the effectiveness of spironolactone therapy after the maze procedure.

Lipopolysaccharide endotoxin potentiates the effect of osmotic stimulation on vasopressin synthesis and secretion in the rat hypothalamus

Vasopressin secreted by magnocellular neurones of the hypothalamic supraoptic and paraventricular nuclei is essential for water balance. In this study, we examined magnocellular neurone responses to osmotic stimulation in vehicle-injected controls or rats receiving an intraperitoneal (i.p.) injection of 250 microg/100 g of lipopolysaccharide (LPS), 3 h or 6 h earlier. LPS injection had no effect on plasma vasopressin concentrations in control rats but it caused marked and transient potentiation of the responses to a single i.p. injection of hypertonic saline (five- and two-fold, 3 and 6 h after LPS, respectively). The enhancement of plasma vasopressin responses was independent of plasma sodium concentrations or changes in blood pressure. Basal vasopressin mRNA expression in the paraventricular and supraoptic nuclei decreased slightly 6 h after LPS injection, without changes in vasopressin transcription as indicated by vasopressin heteronuclear (hn) RNA levels. Parvocellular neurones showed expected increases in vasopressin hnRNA expression following LPS injection and a further increase after i.p. hypertonic saline injection (due to the painful component). In contrast to magnocellular vasopressin mRNA expression, the effects of LPS and hypertonic saline injections in parvocellular neurones were additive and not synergistic. Light microscopic immunohistochemical examination revealed an increase in size of vasopressin but not oxytocin axonal terminals in the neural lobe 3 h after LPS injection. Osmotic stimulation caused marked depletion of vasopressin immunoreactivity in axonal terminals of the neural lobe in both control and LPS-pretreated rats. The changes in vasopressin axon terminals were accompanied by induction of interleukin (IL)-1 beta and IL-6 in the posterior pituitary. The data show that endotoxemia causes morphological and functional alterations of the hypothalamic neurohypophyseal system, resulting in facilitation rather than inhibition of vasopressin synthesis, and secretion in response to osmotic stimulation.

Hypothalamic pituitary adrenal axis and hypothalamic-neurohypophyseal responsiveness in water-deprived rats

The differential effects of osmotic stimulation on magnocellular and parvocellular hypothalamic neurons were studied by analysis of corticotropin-releasing hormone (CRH) and vasopressin (VP) expression in controls and 48-h water-deprived rats subjected to either restraint for 1 h or a single lipopolysaccharide injection (250 microg/100 g). Water deprivation reduced basal CRH mRNA levels but the increments following 4 h of restraint or 6 h lipopolysaccharide (LPS) injection were similar to those in controls. In contrast, water deprivation had no effect on basal VP heteronuclear RNA (hnRNA) and mRNA levels in parvocellular neurons, but responses to restraint or LPS injection were reduced. VP expression in magnocellular paraventricular and supraoptic nuclei, and plasma sodium and vasopressin were higher in water-deprived rats, changes which were unaffected by restraint. LPS injection reduced VP mRNA but not hnRNA levels in magnocellular neurons and increased plasma vasopressin levels only in water-deprived rats independently of changes in plasma sodium. This was accompanied by an increase in vasopressin mRNA content in the posterior pituitary. The data show that the blunted ACTH responses to acute stress during chronic osmotic stimulation are correlated with the inability of parvocellular neurons to increase VP rather than CRH expression. In addition, LPS-induced endotoxemia causes disturbances of the magnocellular vasopressinergic system with an unexpected potentiation of osmotic simulated VP secretion. The lack of increase in VP transcription after LPS and changes in VP mRNA distribution suggest that endotoxemia affect the secretory process at the levels of the neurohypophyseal axon terminal.

The treatment of severe hyponatremia

Severe hyponatremia may be chronic (days) or acute (hours), symptomatic or asymptomatic. Severe chronic symptomatic hyponatremia (serum sodium concentration < 110 to 115 mM/liter) occurs most commonly in the syndrome of inappropriate antidiuretic hormone secretion (SIADH). The treatment of this hyponatremia is a challenge to practicing physicians, in part because an overly rapid correction of hyponatremia may cause brain damage. The latter sometimes takes the form of central pontine myelinolysis (CPM). On the basis of available clinical and experimental literature, the rate of correction of this symptomatic hyponatremia should be no more than 0.5 mM per liter per hour, and the initial treatment should be halted once a mildly hyponatremic range of the serum sodium concentration has been reached (approximately 125 to 130 mM/liter). In contrast, severe chronic asymptomatic hyponatremia may be treated sufficiently by a fluid restriction. On the other hand, severe symptomatic acute hyponatremia should be treated promptly and rapidly, using hypertonic saline, to initially reach a mildly hyponatremic level.

Evaluation of maternal fluid dynamics during tocolytic therapy with ritodrine hydrochloride and magnesium sulfate

OBJECTIVE

The purpose of the study was to observe and compare the effects of ritodrine hydrochloride and magnesium sulfate on maternal fluid dynamics.

STUDY DESIGN

Fourteen women in preterm labor were prospectively studied during tocolytic therapy with either ritodrine hydrochloride or magnesium sulfate. The cardiovascular and renal effects of a pretreatment crystalloid infusion were compared with those observed during tocolytic therapy. Profile analysis and repeated measures of variance were used to analyze the data.

RESULTS

Ritodrine hydrochloride was associated with decreased colloid osmotic pressure, hematocrit, and serum proteins and increased maternal and fetal heart rates. Arginine vasopressin levels increased during the first 2 hours of therapy, then returned to baseline. Sodium excretion was reduced and there was marked fluid retention. Intravenous magnesium sulfate also resulted in a reduction of colloid osmotic pressure, but hematocrit, serum protein concentration, arginine vasopressin, maternal and fetal heart rates, and mean arterial pressure were minimally affected. Sodium excretion increased to a maximum at 6 to 8 hours of treatment, then returned to baseline. A positive fluid balance was also noted in magnesium sulfate-treated patients but to a lesser degree than with ritodrine.

CONCLUSIONS

Sodium retention appears to be the primary cause of plasma volume expansion in ritodrine-treated patients, whereas volume expansion during magnesium sulfate therapy is probably related to intravenous overhydration. In the absence of risk factors for pulmonary capillary membrane injury, available evidence supports volume overload as the principal mechanism for pulmonary edema during tocolytic therapy.