Idiopathic central diabetes insipidus is associated with abnormal blood supply to the posterior pituitary gland caused by vascular impairment of the inferior hypophyseal artery system

Heterogeneity and Dynamics of Vasculature in the Endocrine System During Aging and Disease

The endocrine system consists of several highly vascularized glands that produce and secrete hormones to maintain body homeostasis and regulate a range of bodily functions and processes, including growth, metabolism and development. The dense and highly vascularized capillary network functions as the main transport system for hormones and regulatory factors to enable efficient endocrine function. The specialized capillary types provide the microenvironments to support stem and progenitor cells, by regulating their survival, maintenance and differentiation. Moreover, the vasculature interacts with endocrine cells supporting their endocrine function. However, the structure and niche function of vasculature in endocrine tissues remain poorly understood. Aging and endocrine disorders are associated with vascular perturbations. Understanding the cellular and molecular cues driving the disease, and age-related vascular perturbations hold potential to manage or even treat endocrine disorders and comorbidities associated with aging. This review aims to describe the structure and niche functions of the vasculature in various endocrine glands and define the vascular changes in aging and endocrine disorders.

Central diabetes insipidus in children: Diagnosis and management

Central diabetes insipidus (CDI) is a complex disorder in which large volumes of dilute urine are excreted due to arginine-vasopressin deficiency, and it is caused by a variety of conditions (genetic, congenital, inflammatory, neoplastic, traumatic) that arise mainly from the hypothalamus. The differential diagnosis between diseases presenting with polyuria and polydipsia is challenging and requires a detailed medical history, physical examination, biochemical approach, imaging studies and, in some cases, histological confirmation. Magnetic resonance imaging is the gold standard method for evaluating the sellar-suprasellar region in CDI. Pituitary stalk size at presentation is variable and can change over time, depending on the underlying condition, and other brain areas or other organs - in specific diseases - may become involved during follow up. An early diagnosis and treatment are preferable in order to avoid central nervous system damage and the risk of dissemination of germ cell tumor, or progression of Langerhans Cell Histiocytosis, and in order to start treatment of additional pituitary defects without further delay. This review focuses on current diagnostic work-up and on the role of neuroimaging in the differential diagnosis of CDI in children and adolescents. It provides an update on the best approach for diagnosis - including novel biochemical markers such as copeptin - treatment and follow up of children and adolescents with CDI; it also describes the best approach to challenging situations such as post-surgical patients, adipsic patients, patients undergoing chemotherapy and/or in critical care.

Arterial Supply to the Pituitary Gland: A Comprehensive Review

Knowledge of the blood supply to the pituitary gland is important for clinicians and surgeons. Therefore, a good working knowledge of this anatomy is important. The goal of this article was to review current anatomic knowledge of the blood supply to the pituitary gland and its clinical relevance.

Transient Central Diabetes Insipidus after Discontinuation of Vasopressin

Central diabetes insipidus (CDI) is an uncommon condition resulting from lack of vasopressin secretion from the posterior pituitary gland typically caused by some form of destruction of the gland. Here we present a case of transient CDI after discontinuation of vasopressin used for septic shock without evidence of overt pituitary damage. Serum sodium concentration peaked at 160 mmol/L in the setting of polyuria within days of vasopressin discontinuation without identified alternative etiologies. Sodium levels and urine output normalized with administration of desmopressin with continued stability after desmopressin was discontinued. This is one of few reported cases of diabetes insipidus occurring after discontinuation of vasopressin and the rapid and profound response to desmopressin in this case proves a central etiology. This case allows for speculation into predisposing risk factors for this phenomenon including preexisting neurological disease.

Role of MRI T2-DRIVE in the assessment of pituitary stalk abnormalities without gadolinium in pituitary diseases

OBJECTIVE

To investigate the role of T2-DRIVE MRI sequence in the accurate measurement of pituitary stalk (PS) size and the identification of PS abnormalities in patients with hypothalamic-pituitary disorders without the use of gadolinium.

DESIGN

This was a retrospective study conducted on 242 patients who underwent MRI due to pituitary dysfunction between 2006 and 2015. Among 135 eligible patients, 102 showed eutopic posterior pituitary (PP) gland and 33 showed 'ectopic' PP (EPP).

METHODS

Two readers independently measured the size of PS in patients with eutopic PP at the proximal, midpoint and distal levels on pre- and post-contrast T1-weighted as well as T2-DRIVE images; PS visibility was assessed on pre-contrast T1 and T2-DRIVE sequences in those with EPP. The length, height, width and volume of the anterior pituitary (AP), PP height and length and PP area were analyzed.

RESULTS

Significant agreement between the two readers was obtained for T2-DRIVE PS measurements in patients with 'eutopic' PP; a significant difference was demonstrated between the intraclass correlation coefficient calculated on the T2-DRIVE and the T1-pre- and post-contrast sequences. The percentage of PS identified by T2-DRIVE in EPP patients was 72.7% compared to 30.3% of T1 pre-contrast sequences. A significant association was found between the visibility of PS on T2-DRIVE and the height of AP.

CONCLUSION

T2-DRIVE sequence is extremely precise and reliable for the evaluation of PS size and the recognition of PS abnormalities; the use of gadolinium-based contrast media does not add significant information and may thus be avoided.

Classical and non-classical causes of GH deficiency in the paediatric age

Growth hormone deficiency (GHD) may result from a failure of hypothalamic GHRH production or release, from congenital disorders of pituitary development, or from central nervous system insults including tumors, surgery, trauma, radiation or infiltration from inflammatory diseases. Idiopathic, isolated GHD is the most common sporadic form of hypopituitarism. GHD may also occur in combination with other pituitary hormone deficiencies, and is often referred to as hypopituitarism, combined pituitary hormone deficiency (CPHD), multiple pituitary hormone deficiency (MPHD) or panhypopituitarism. Children without any identifiable cause of their GHD are commonly labeled as having idiopathic hypopituitarism. MRI imaging is the technique of choice in the diagnosis of children with hypopituitarism. Marked differences in MRI pituitary gland morphology suggest different etiologies of GHD and different prognoses. Pituitary stalk agenesis and ectopic posterior pituitary (EPP) are specific markers of permanent GHD, and patients with these MRI findings show a different clinical and endocrine outcome compared to those with normal pituitary anatomy or hypoplastic pituitary alone. Furthermore, the classic triad of ectopic posterior pituitary gland, pituitary stalk hypoplasia/agenesis, and anterior pituitary gland hypoplasia is generally associated with permanent GHD. T2 DRIVE images aid in the identification of pituitary stalk without the use of contrast medium administration. Future developments in imaging techniques will undoubtedly reveal additional insights. Mutations in a number of genes encoding transcription factors - such as HESX1, SOX2, SOX3, LHX3, LHX4, PROP1, POU1F1, PITX, GLI3, GLI2, OTX2, ARNT2, IGSF1, FGF8, FGFR1, PROKR2, PROK2, CHD7, WDR11, NFKB2, PAX6, TCF7L1, IFT72, GPR161 and CDON - have been associated with pituitary dysfunction and abnormal pituitary gland development; the correlation of genetic mutations to endocrine and MRI phenotypes has improved our knowledge of pituitary development and management of patients with hypopituitarism, both in terms of possible genetic counseling, and of early diagnosis of evolving anterior pituitary hormone deficiencies.

Diabetes insipidus: The other diabetes

Diabetes insipidus (DI) is a hereditary or acquired condition which disrupts normal life of persons with the condition; disruption is due to increased thirst and passing of large volumes of urine, even at night. A systematic search of literature for DI was carried out using the PubMed database for the purpose of this review. Central DI due to impaired secretion of arginine vasopressin (AVP) could result from traumatic brain injury, surgery, or tumors whereas nephrogenic DI due to failure of the kidney to respond to AVP is usually inherited. The earliest treatment was posterior pituitary extracts containing vasopressin and oxytocin. The synthetic analog of vasopressin, desmopressin has several benefits over vasopressin. Desmopressin was initially available as intranasal preparation, but now the oral tablet and melt formulations have gained significance, with benefits such as ease of administration and stability at room temperature. Other molecules used for treatment include chlorpropamide, carbamazepine, thiazide diuretics, indapamide, clofibrate, indomethacin, and amiloride. However, desmopressin remains the most widely used drug for the treatment of DI. This review covers the physiology of water balance, causes of DI and various treatment modalities available, with a special focus on desmopressin.

Central diabetes insipidus following cardiopulmonary arrest in a dog

OBJECTIVE

To describe a clinical case of transient central diabetes insipidus (CDI) occurring post cardiopulmonary arrest (CPA) in a dog.

CASE SUMMARY

An 8-week-old dog presented for intensive care after successful resuscitation following CPA. The patient exhibited neurologic deficits at initial presentation and over the following days developed marked polyuria, isosthenuria, and low urine osmolality. Treatment with synthetic vasopressin resulted in a reduction in urine output, increase in urine specific gravity (>50%), and increase in urine osmolality, suggesting a diagnosis of partial CDI. Clinical signs resolved over the following weeks and treatment was discontinued.

NEW OR UNIQUE INFORMATION PROVIDED

CPA has been described as a cause of ischemic injury to the pituitary gland resulting in CDI in people. To the authors' knowledge, this is the first report of a dog developing transient partial CDI following CPA and successful resuscitation.

Management of diabetes insipidus and adipsia in the child

Central diabetes insipidus (CDI) is a complex and heterogeneous clinical syndrome affecting the hypothalamic-neurohypophyseal network and water balance. A recent national surveillance in Denmark showed a prevalence rate of twenty-three CDI patients per 100,000 inhabitants in five years. The differential diagnosis between several presenting conditions with polyuria and polydipsia is puzzling, and the etiological diagnosis of CDI remains a challenge before the identification of an underlying cause. For clinical practice, a timely diagnosis for initiating specific treatment in order to avoid central nervous system damage, additional pituitary defects and the risk of dissemination of germ cell tumor is advisable. Proper etiological diagnosis can be achieved via a series of steps that start with careful clinical observation of several signs and endocrine symptoms and then progress to more sophisticated imaging tools. This review summarizes the best practice and approach for the diagnosis and treatment of patients with CDI.

Early-onset central diabetes insipidus is associated with de novo arginine vasopressin-neurophysin II or Wolfram syndrome 1 gene mutations

OBJECTIVE

Idiopathic early-onset central diabetes insipidus (CDI) might be due to mutations of arginine vasopressin-neurophysin II (AVP-NPII (AVP)) or wolframin (WFS1) genes.

DESIGN AND METHODS

Sequencing of AVP and WFS1 genes was performed in nine children with CDI, aged between 9 and 68 months, and negative family history for polyuria and polydipsia.

RESULTS

Two patients carried a mutation in the AVP gene: a heterozygous G-to-T transition at nucleotide position 322 of exon 2 (c.322G>T) resulting in a stop codon at position 108 (p.Glu108X), and a novel deletion from nucleotide 52 to 54 (c.52_54delTCC) producing a deletion of a serine at position 18 (p.Ser18del) of the AVP pre-prohormone signal peptide. A third patient carried two heterozygous mutations in the WFS1 gene localized on different alleles. The first change was A-to-G transition at nucleotide 997 in exon 8 (c.997A>G), resulting in a valine residue at position 333 in place of isoleucine (p.Ile333Val). The second novel mutation was a 3 bp insertion in exon 8, c.2392_2393insACG causing the addition of an aspartate residue at position 797 and the maintenance of the correct open reading frame (p. Asp797_Val798insAsp). While similar WFS1 protein levels were detected in fibroblasts from healthy subjects and from the patient and his parents, a major sensitivity to staurosporine-induced apoptosis was observed in the patient fibroblasts as well as in patients with Wolfram syndrome.

CONCLUSIONS

Early-onset CDI is associated with de novo mutations of the AVP gene and with hereditary WFS1 gene changes. These findings have valuable implications for management and genetic counseling.

3D dynamic pituitary MR imaging with CAIPIRINHA: initial experience and comparison with 2D dynamic MR imaging

OBJECTIVES

To evaluate the validity of 3D dynamic pituitary MR imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), with special emphasis on demarcation of pituitary posterior lobe and stalk.

METHODS

Participants comprised 32 patients who underwent dynamic pituitary MR imaging due to pituitary or parasellar lesions. 3D dynamic MR with CAIPIRINHA was performed at 3T with 20-s-interval, precontrast, 1st to 5th dynamic images. Normalized values and enhanced ratios (dynamic postcontrast image values divided by precontrast ones) were compared between 3D and 2D dynamic MR imaging for patients with visual identification of posterior lobe and stalk.

RESULTS

In 3D, stalk was identified in 29 patients and unidentified in 3, and posterior lobe was identified in 28 and unidentified in 4. In 2D, stalk was identified in 26 patients and unidentified in 6 patients, and posterior lobe was identified in 15 and unidentified in 17. Normalized values of pituitary posterior lobe and stalk were higher in 3D than 2D (P<0.001). No significant difference in enhancement ratio was seen between 3D and 2D.

CONCLUSIONS

3D dynamic pituitary MR provided better identification and higher normalized values of pituitary posterior lobe and stalk than 2D.

Central diabetes insipidus in children and young adults: etiological diagnosis and long-term outcome of idiopathic cases

CONTEXT

Central diabetes insipidus (CDI) is considered idiopathic in 20% to 50% of affected subjects.

OBJECTIVE

The purpose of this study was to determine whether a systematic diagnostic workup could achieve better etiologic diagnosis in children and adolescents presenting with polyuria and polydipsia.

DESIGN AND SETTING

This is a prospective study conducted at a tertiary referral center. Patients underwent clinical and endocrine evaluations every 6 months and neuroimaging every 6 months for 2 years and yearly for 3 years. Endocrine function and neuroimaging were also reassessed after adult height achievement.

PARTICIPANTS

A total of 85 consecutive patients with CDI were enrolled at a median age of 7.5 years; those with idiopathic CDI were stratified based on pituitary stalk thickness.

MAIN OUTCOME MEASURES

To establish the etiology of CDI, we determined the time lag between its onset and the specific diagnosis, the long-term impact on pituitary function, and the overall long-term outcomes.

RESULTS

Of the subjects, 24 (28.2%) received an etiologic diagnosis at presentation and 11 (13%) within 2.5 years (n = 7 germinomas and n = 4 Langerhans cell histiocytosis), 7 (8.2%) were lost to follow-up, and 43 (50.6%) were considered to have idiopathic disease and were followed until the median age of 17.3 years. Neuroimaging identified 40 of 43 patients with self-limited inflammatory/autoimmune pituitary stalk thickness within the first 6 months, the severity of which was significantly correlated to pituitary dysfunction. The probability of >10-year-survival without an anterior pituitary defect was related to the severity of pituitary stalk thickness, and 53% showed permanent anterior pituitary defects. Three patients developed Langerhans cell histiocytosis and 1 developed Hodgkin lymphoma after a median of 9 and 13 years, respectively.

CONCLUSIONS

A diagnostic etiology was achieved in 96% of patients with CDI. Risk stratification based on the degree of pituitary stalk thickness is of prognostic value for long-term outcomes including permanent pituitary dysfunction. New guidance is provided for the management of these patients.

Transient central diabetes insipidus following ischemic stroke

Central Diabetes Insipidus (CDI) following ischemic infarction of the brain has been described as a rare presentation. Posterior pituitary ischemia has also been postulated as a possible cause of idiopathic CDI. We encountered a young male with bilateral extensive ischemic infarction sustained at high altitude, who had transient polyuria due to central diabetes insipidus, requiring desmopressin therapy. DI completely resolved during the course of his neurological recovery.

Recent insights into the cell biology of thyroid angiofollicular units

In thyrocytes, cell polarity is of crucial importance for proper thyroid function. Many intrinsic mechanisms of self-regulation control how the key players involved in thyroid hormone (TH) biosynthesis interact in apical microvilli, so that hazardous biochemical processes may occur without detriment to the cell. In some pathological conditions, this enzymatic complex is disrupted, with some components abnormally activated into the cytoplasm, which can lead to further morphological and functional breakdown. When iodine intake is altered, autoregulatory mechanisms outside the thyrocytes are activated. They involve adjacent capillaries that, together with thyrocytes, form the angiofollicular units (AFUs) that can be considered as the functional and morphological units of the thyroid. In response to iodine shortage, a rapid expansion of the microvasculature occurs, which, in addition to nutrients and oxygen, optimizes iodide supply. These changes are triggered by angiogenic signals released from thyrocytes via a reactive oxygen species/hypoxia-inducible factor/vascular endothelial growth factor pathway. When intra- and extrathyrocyte autoregulation fails, other forms of adaptation arise, such as euthyroid goiters. From onset, goiters are morphologically and functionally heterogeneous due to the polyclonal nature of the cells, with nodules distributed around areas of quiescent AFUs containing globules of compact thyroglobulin (Tg) and surrounded by a hypotrophic microvasculature. Upon TSH stimulation, quiescent AFUs are activated with Tg globules undergoing fragmentation into soluble Tg, proteins involved in TH biosynthesis being expressed and the local microvascular network extending. Over time and depending on physiological needs, AFUs may undergo repetitive phases of high, moderate, or low cell and tissue activity, which may ultimately culminate in multinodular goiters.

Polyuria with the Concurrent manifestation of Central Diabetes Insipidus (CDI) & Type 2 Diabetes Mellitus (DM)

We report a rare case of the concurrent manifestation of central diabetes insipidus (CDI) and type 2 diabetes mellitus (DM). A 56 year-old man was diagnosed as a type 2 DM on the basis of hyperglycemia with polyuria and polydipsia at a local clinic two months ago and started an oral hypoglycemic medication, but resulted in no symptomatic improvement at all. Upon admission to the university hospital, the patient's initial fasting blood sugar level was 140 mg/dL, and he showed polydipsic and polyuric conditions more than 8 L urine/day. Despite the hyperglycemia controlled with metformin and diet, his symptoms persisted. Further investigations including water deprivation test confirmed the coexisting CDI of unknown origin, and the patient's symptoms including an intense thirst were markedly improved by desmopressin nasal spray (10 µg/day). The possibility of a common origin of CDI and type 2 DM is raised in a review of the few relevant adult cases in the literature.

[Behçet disease with isolated ACTH deficiency]

We report a case of a patient with longstanding Behçet disease, with neurological symptoms predominantly, who became hospitalized for adrenal insufficiency, caused by isolated deficiency of corticotropin (DAACTH). DAACTH is a typical characteristic of hypophysitis, reported in association with many autoimmune diseases. Nevertheless, hypothalamic-pituitary injury in Behçet disease is exceptional. We review the literature and possible mechanisms of this association until now not reported.

Clinical features and molecular analysis of arginine-vasopressin neurophysin II gene in long-term follow-up patients with idiopathic central diabetes insipidus

INTRODUCTION: Central diabetes insipidus (DI) characterized by polyuria, polydipsia and inability to concentrate urine, has different etiologies including genetic, autoimmune, post-traumatic, among other causes. Autosomal dominant central DI presents the clinical feature of a progressive decline of arginine-vasopressin (AVP) secretion. OBJECTIVE: In this study, we characterized the clinical features and sequenced the AVP-NPII gene of seven long-term follow-up patients with idiopathic central DI in an attempt to determine whether a genetic cause would be involved. METHODS: The diagnosis of central DI was established by fluid deprivation test and hyper-tonic saline infusion. For molecular analysis, genomic DNA was extracted and the AVP-NPII gene was amplified by polymerase chain reaction and sequenced. RESULTS: Sequencing analysis revealed a homozygous guanine insertion in the intron 2 (IVS2 +28 InsG) of the AVP-NPII gene in four patients, which represents an alternative gene assembly. No mutation in the code region of the AVP-NPII gene was found. CONCLUSIONS: The homozygous guanine insertion in intron 2 (IVS2 +28 InsG) is unlikely to contribute to the AVP-NPII gene modulation in DI. In addition, the etiology of idiopathic central DI in children may not be apparent even after long-term follow-up, and requires continuous etiological surveillance.

Central Diabetes Insipidus: A Rare Perioperative Cause of Severe Hypernatraemia

In this case report we describe the management of severe hypernatraemia following inadvertent water restriction. A 21-year-old woman with no reported medical history presented on transfer from an outside hospital with a complex volar upper extremity injury. Management both operatively and postoperatively involved a prolonged period of fasting which limited her access to drinking water. Collateral history revealed that she had previously drunk copious amounts of water during the course of any given day and this had served to alleviate the dramatic symptoms of hypernatraemia that were rapidly manifest when her normal intake was curtailed. We outline the fluid management, administration of desmopressin and her subsequent recovery. A literature review of the management of central diabetes insipidus is also covered.

The diagnosis of children with central diabetes insipidus

Central diabetes insipidus is the end result of a number of different diseases that affect the hypothalamic-neurohypophyseal system. In many patients, especially children and young adults, it is caused by the destruction or degeneration of neurons that originate in the supraoptic and paraventricular nuclei of the hypothalamus. The known causes of these lesions include germinoma or craniopharyngioma; Langerhans cell histiocytosis; local inflammatory, autoimmune or vascular diseases; trauma resulting from surgery or an accident; sarcoidosis; metastases; and midline cerebral and cranial malformations. In rare cases, genetic defects in AVP synthesis that are inherited as autosomal dominant, autosomal recessive or X-linked recessive traits are the underlying cause. Accurate diagnostic differentiation is essential for both safe and effective disease management. Proper etiological diagnosis can be achieved via a series of steps that start with clinical observations and then progress, as needed, to more sophisticated methods. Indeed, magnetic resonance imaging (MRI) represents the examination method of choice for evaluating hypothalamic-pituitary-related endocrine diseases due to its ability to provide strongly-contrasted high-resolution multi-planar and spatial images. Specifically, MRI allows a detailed and precise anatomical study of the pituitary gland by differentiating between the anterior and posterior pituitary lobes. MRI identification of pituitary hyperintensity in the posterior part of the sella, now considered to be a clear marker of neurohypophyseal functional integrity, together with careful analysis of pituitary stalk shape and size, have provided the most striking recent findings contributing to the diagnosis and understanding of some forms of 'idiopathic' central diabetes insipidus.

Diabetes insipidus

Water balance is precisely regulated by vasopressin, thirst and the kidneys; plasma osmolality is maintained within a narrow range, despite large variations in normal water intake and loss. Disruption of these finely balanced mechanisms is common, however, and can be precipitated by various disease states. Diabetes insipidus is a disease process with several underlying pathogenic mechanisms--all ultimately resulting in excretion of large volumes of dilute urine. This review will discuss the pathophysiology, diagnosis and treatment of diabetes insipidus, with emphasis on disorders of osmoregulation following neurosurgery of the pituitary and hypothalamus.

Idiopathic central diabetes insipidus in children and young adults is commonly associated with vasopressin-cell antibodies and markers of autoimmunity

OBJECTIVES

Autoimmune targeting of hypothalamic-neurohypophyseal structures in children and young adults with posterior pituitary and anterior pituitary dysfunction, as well as pituitary stalk involvement, are not yet completely understood.

DESIGN

We aimed to (1) evaluate the presence of circulating vasopressin-cell autoantibodies (AVPc-Abs) in young patients with central diabetes insipidus (CDI), (2) detect organ-specific autoantibodies as markers of autoimmunity, and (3) define the relationship between immune markers and neuroimaging findings.

PATIENTS

Twenty patients were evaluated at a median age of 16.3 years. Twelve patients had idiopathic CDI, six had Langerhans cell histiocytosis (LCH) and two had germinoma. AVPc-Abs were evaluated in 40 healthy children. Magnetic resonance imaging (MRI) of the hypothalamic-pituitary region was performed longitudinally in all subjects.

MEASUREMENTS

Circulating arginine vasopressin (AVP), protein tyrosine phosphatase (IA2), glutamic acid decarboxylase (GAD), 21-hydroxylase (21-OH), endomysium antibodies (EMA), parietal cell (PCA), thyroid peroxidase (TPO), thyroglobulin (TG) and TSH-receptor (TSHr) autoantibodies were evaluated.

RESULTS

Circulating AVPc-Abs were found in 15 patients (75%), nine with idiopathic CDI, four with LCH and two with germinoma; the pituitary stalk was involved in most of them. Five patients with idiopathic CDI showed a persistence of AVPc-Abs during follow-up and one became positive subsequently. Serum IA2 autoantibodies were demonstrated in 14 patients (70%) and 21-OH autoantibodies in three of them.

CONCLUSION

In idiopathic CDI, circulating AVPc-Abs suggest an autoimmune involvement of the neurohypophyseal system. The identification of AVPc-Abs in subjects who could have either idiopathic CDI or LCH or germinoma, however, indicates that AVPc-Abs cannot be considered a completely reliable marker of autoimmune CDI. Thus, close clinical and MRI follow-up are needed because AVPc-Abs may mask germinoma or LCH.

External causes of metabolic disorders

Common medical conditions, such as head trauma, malignancy,and pregnancy may be associated with rarely seen metabolic emergencies that require prompt recognition and therapy. Although care of the primary disorder is the focus of initial management,identification of the associated endocrinopathy is important. These clinical syndromes, although uncommon, must be considered when evaluating patients, as prompt treatment may minimize the mortality and morbidity of these conditions.

Current perspective on the pathogenesis of central diabetes insipidus

Diabetes insipidus is a heterogeneous condition characterised by polyuria and polydipsia caused by a lack of secretion of vasopressin, its physiological suppression following excessive water intake, or kidney resistance to its action. The clinical and laboratory diagnosis is confirmed by standard tests, but recent advances in molecular biology and imaging techniques have shed new light on the pathophysiology of this disease. In many patients, central diabetes insipidus is caused by a germinoma or craniopharyngioma; Langerhans' cell histiocytosis and sarcoidosis of the central nervous system; local inflammatory, autoimmune or vascular diseases; trauma from surgery or accident; and, rarely, genetic defects in vasopressin biosynthesis inherited as autosomal dominant or X-linked recessive traits. Thirty to fifty percent of cases are considered idiopathic. Tumour-associated central diabetes insipidus is uncommon in children younger than 5 years old. Biopsy of enlarged pituitary stalk should be reserved for patients with hypothalamic-pituitary mass and progressive thickening of the pituitary stalk since spontaneous recovery may occur. Molecular biology in selected patients may identify those with apparently idiopathic diabetes insipidus carrying the vasopressin-neurophysin II gene mutation.