Rabphilin-3A as a Targeted Autoantigen in Lymphocytic Infundibulo-neurohypophysitis

A Pregnant Woman with Excess Vasopressinase-Induced Diabetes Insipidus Complicated by Central Diabetes Insipidus like Lymphocytic Infundibulo-Neurohypophysitis

Background

Gestational diabetes insipidus (DI) is a very rare complication of pregnancy. We present a case of gestational DI combining two different types of DI. Case Presentation. A 39-year-old pregnant woman suddenly presented with thirst, polydipsia, and polyuria after 31 gestation weeks (GWs). Based on laboratory findings of hypotonic urine (78 mOsm/kgH2O) with higher plasma osmolality (298 mOsm/kgH2O) and higher serum sodium levels (149 mEq/L), gestational DI was suspected, and the clinical course was monitored without therapy until the results of a measurement of plasma arginine vasopressin (AVP) levels were available. However, she subsequently developed acute prerenal failure and underwent an emergency cesarean section at 34 GWs. Her resected placenta weighed 920 g, nearly twice the normal weight. Immediately following delivery, intranasal 1-desamino-8-D-arginine vasopressin was administered, and her symptoms promptly disappeared. Afterward, her predelivery plasma AVP level was found to have been inappropriately low (0.7 pg/mL) given her serum sodium level. The patient's serum vasopressinase level just before delivery was 2,855 ng/mL, more than 1,000 times the upper limit of the normal range, suggesting excess vasopressinase-induced DI. The presence of anti-rabphilin-3A antibodies in the patient's blood, a hypertonic saline infusion test result, and loss of the high-intensity signal of the posterior pituitary on fat-suppressed T1-weighted magnetic resonance images without thickening of the stalk and enlargement of the neurohypophysis suggested concurrent central DI-like lymphocytic infundibulo-neurohypophysitis (LINH).

Conclusion

In addition to the degradation of AVP by excess placental vasopressinase due to the enlarged placenta, an insufficient compensatory increase in AVP secretion from the posterior pituitary gland due to LINH-like pathogenesis might have led to DI symptoms.

Absence of anti-rabphilin-3A antibodies in children and young adults with idiopathic central diabetes insipidus: a potential clue to elucidating a tumor etiology

BACKGROUND

Central diabetes insipidus (CDI) is a rare condition caused by various underlying diseases, including neoplasms, autoimmune diseases, and infiltrative diseases. Differentiating between CDI etiologies is difficult. What has initially been classified as "idiopathic" central diabetes insipidus might in fact underlie various pathogenic mechanisms that are less understood to date and/or are not obvious at initial presentation. Therefore, even if idiopathic CDI is diagnosed at the time of onset, it is common for tumors such as germinoma to develop during surveillance. Crucially, a delayed diagnosis of germinoma may be associated with a worse prognosis. Recently, the presence of anti-rabphilin-3A antibodies has been found to be a highly sensitive and specific marker of lymphocytic infundibuloneurohypophysitis, an autoimmune-mediated CDI.

CASE PRESENTATION

We herein present two cases, namely, a 13-year-old boy (patient 1) and a 19-year-old young man (patient 2) who were diagnosed with idiopathic CDI. In both patients, panhypopituitarism developed. Magnetic resonance imaging revealed pituitary stalk thickening and pituitary swelling approximately 1 1/2 years after the onset of CDI. Western blotting did not reveal the presence of anti-rabphilin-3A antibodies in serum in either patient, suggesting that autoimmune mechanisms might not be involved. Both patients were subsequently diagnosed with germinoma on pathological examination. They received chemotherapy, followed by radiation therapy. Notably, testosterone and insulin-like growth factor-1 levels normalized, and libido and beard growth recovered after chemoradiotherapy in patient 2.

CONCLUSION

Our data suggest that the absence of anti-rabphilin-3A antibodies in young patients clinically diagnosed with idiopathic CDI may increase the probability of the development of non-lymphocytic lesions, including germinoma. We thus recommend a more attentive approach at the onset of these diseases.

Endocrine Side Effects in Patients Treated with Immune Checkpoint Inhibitors: A Narrative Review

Checkpoint inhibitors are monoclonal antibodies that elicit an anti-tumor response by stimulating immune system. Their use has improved the treatment of different types of cancer such as melanoma, breast carcinoma, lung, stomach, colon, liver, renal cell carcinoma, and Hodgkin's lymphoma, but several adverse events have been reported. Although the etiology of these effects is not completely understood, an uncontrolled activation of the immune system has been postulated. Indeed, some studies showed a cross reactivity of T cells, which acted against tumor antigens as well as antigens in the tissues of patients who developed immune-related adverse events. Despite the known possibility of developing immune-related adverse events, early diagnosis, monitoring during therapy, and treatment are fundamental for the best supportive care and administration of immune checkpoint inhibitors. The aim of this review is to guide the clinician in early diagnosis, management, and treatment of the endocrinological adverse effects in the major endocrine glands (thyroid, pituitary, adrenal, endocrine pancreas, and parathyroid).

Shared Pathogenicity Features and Sequences between EBV, SARS-CoV-2, and HLA Class I Molecule-binding Motifs with a Potential Role in Autoimmunity

Epstein-Barr virus (EBV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are extraordinary in their ability to activate autoimmunity as well as to induce diverse autoimmune diseases. Here we reviewed the current knowledge on their relation. Further, we suggested that molecular mimicry could be a possible common mechanism of autoimmunity induction in the susceptible individuals infected with SARS-CoV-2. Molecular mimicry between SARS-CoV-2 and human proteins, and EBV and human proteins, are present. Besides, relation of the pathogenicity associated with both coronavirus diseases and EBV supports the notion. As a proof-of-the-concept, we investigated 8mer sequences with shared 5mers of SARS-CoV-2, EBV, and human proteins, which were predicted as epitopes binding to the same human leukocyte antigen (HLA) supertype representatives. We identified significant number of human peptide sequences with predicted-affinities to the HLA-A*02:01 allele. Rest of the peptide sequences had predicted-affinities to the HLA-A*02:01, HLA-B*40:01, HLA-B*27:05, HLA-A*01:01, and HLA-B*39:01 alleles. Carriers of these serotypes can be under a higher risk of autoimmune response induction upon getting infected, through molecular mimicry-based mechanisms common to SARS-CoV-2 and EBV infections. We additionally reviewed established associations of the identified proteins with the EBV-related pathogenicity and with the autoimmune diseases.

Unveiling the Etiopathogenic Spectrum of Hypophysitis: A Narrative Review

Hypophysitis, a rare inflammatory disorder of the pituitary gland, has seen an uptick in reported cases in recent years. Our objective is to summarize the most recent research on the etiopathogenesis, molecular mechanisms, and genetics of both primary and secondary hypophysitis. Primary autoimmune hypophysitis (PAH): During the acute phase of the disease, the pituitary gland in enlarged due to the infiltration of T and B lymphocytes. The chronic phase is characterized by progressive and irreversible pituitary atrophy. APA may play a role in the management, diagnosis, and prognosis of PAH. Specific autoantibodies such as anti-GH, anti-PIT-1, and anti-T-PIT have been found in patients with hypophysitis and hypopituitarism. A recent study suggested that a mechanism of escaping clonal deletion and mounting an immune response against self antigens can explain the unusual nature of the immune response observed in PAH patients. A cytokine array shows the presence of gamma-interferon and interleukin-17. Patients carrying mutations in the PIT1 or PROP1 genes may present PAH. Individuals carrying the HLA DQ8 haplotype are four times more likely to develop PAH. Immune checkpoint inhibitors induce hypophysitis (IIHs): IIHs is an increasingly frequent toxicity of in patients on treatment with inhibitors targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed cell death-1 (PD-1). ICIs inhibit the CTLA-4 pathway, leading to overactivation of T lymphocytes. The binding of PD-1/PD-L1 suppresses the activity of T cells, promotes the conversion of T-helpers into T-regulatory cells, and activates pro-survival signaling pathways in cancer cells. Cytokines play a crucial role in IIHs. B-cell infiltration has been observed in IIHs, suggesting that antibody-mediated pituitary injury may contribute. Genetic polymorphisms of CTLA-4 and PD-1 genes can increase the risk of IIHs. HLA alleles may also be involved in the onset of IIHs; this HLA association presents a possible alternative mechanistic hypothesis. IIHs may also be linked to a paraneoplastic syndrome triggered by ectopic expression of pituitary specific antigens. SARS-CoV-2-related hypophysitis: Recently, the literature has reported occurrences of hypophysitis associated with the SARS-CoV-2 virus; long COVID-19 may also present as infundibulo-neuro-hypophysitis. The virus enters the central nervous system because of its distinct interaction with angiotensin-converting enzyme receptors via spike proteins binding the capillary endothelium, and it directly damages the pituitary cells. The effect of SARS-CoV-2 can occur indirectly through inflammation and the release of cytokines. The exact mechanism remains ambiguous. The available data on endocrine complications associated with the SARS-CoV-2 vaccine are scant. Nonetheless, isolated cases of hypophysitis have been documented. Treatment of hypophysitis: Glucocorticoids are the cornerstone in managing primary hypophysitis, given their targeted action on inflammation. A better understanding of the etiopathogenesis and molecular mechanism of hypophysitis can lead to more effective and personalized treatment strategies.

Autoantibodies involved in primary and secondary adrenal insufficiency following treatment with immune checkpoint inhibitors

Primary and secondary adrenal insufficiency (AI) are commonly known immune-related adverse events following treatment with immune checkpoint inhibitors (ICIs), and are clinically relevant due to their morbidity and potential mortality. For this reason, upfront identification of patients susceptible for ICI-induced AI could be a step in improving patient's safety. Multiple studies have focused on the identification of novel biomarkers for ICI-induced AI, including autoantibodies, which may be involved in ICI-induced AI as a result of the T-cell-mediated activation of autoreactive B cells. This review highlights the currently described autoantibodies that may be involved in either primary [e.g. anti-21-hydroxylase, anti-17α-hydroxylase, anti-P450scc, anti-aromatic L-amino acid decarboxylase (AADC), anti-interferon (IFN)α and anti-IFNΩ] or secondary AI [e.g. anti-guanine nucleotide-binding protein G(olf) subunit alpha (GNAL), anti-integral membrane protein 2B (ITM2B), anti-zinc finger CCHC-type containing 8 (ZCCHC8), anti-pro-opiomelanocortin (POMC), anti-TPIT (corticotroph-specific transcription factor), anti-pituitary-specific transcriptional factor-1 (PIT-1) and others], and discusses the current evidence concerning their role as biomarker for ICI-induced AI. Standardized autoantibody measurements in patients (to be) treated with ICIs would be a clinically accessible and patient-friendly screening method to identify the patients at risk, and could change the management of ICI-induced AI.

A Case of Lymphocytic Infundibulo-neurohypophysitis Exhibiting Spontaneous Regression

Lymphocytic infundibulo-neurohypophysitis (LINH) is a rare autoimmune inflammatory process that selectively affects the neurohypophysis and the pituitary stalk, typically presenting with central diabetes insipidus (CDI). LINH is considered underdiagnosed because the definitive diagnosis requires invasive pituitary surgery with a high risk of complications. We present a case of CDI resulting from LINH, which was treated with conservative management, eschewing both glucocorticoid treatment and pituitary surgery. At presentation, the hormonal assessment indicated the presence of CDI without anterior pituitary dysfunction. Magnetic resonance imaging revealed stalk thickening without a posterior pituitary bright spot, and anti-rabphilin-3A antibodies were positive in serum. Collectively, we made a diagnosis of LINH. Considering that the patient did not exhibit any symptoms of mass effect, we chose conservative treatment with desmopressin acetate. One year later, the stalk thickening regressed spontaneously without surgical or glucocorticoid treatment, although the posterior pituitary bright spot remained absent, and CDI did not improve. The inflammatory process of LINH is mostly self-limited and recovers spontaneously, whereas life-long desmopressin treatment may be required because of pituitary stalk fibrosis and atrophy. Our case highlights the importance of noninvasive diagnosis and careful follow-up in preventing unnecessary interventions for patients with LINH.

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

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

Approach to a case with an unusual cause of hypopituitarism

Hypopituitarism refers to insufficiency of one or more hormones of the pituitary and can be due to myriad causes. The clinical and radiological spectrum of the condition is heterogeneous, based on the age, gender, clinical setting and/or other past medical history. Hypopituitarism includes central hypocortisolism, hypothyroidism, hypogonadism and growth hormone deficiency. Both hypo- and hyperprolactinemia can be associated with hypopituitarism, with low prolactin signifying more extensive pituitary damage. Posterior pituitary insufficiency (arginine vasopressin deficiency), occurs either in isolation or with anterior pituitary hormone deficiency. Clinical symptomatology of hypopituitarism is usually non-specific and insidious in onset and progression. Overall, the most common cause of hypopituitarism is a pituitary adenoma and/or its management (surgery, radiotherapy, pharmacotherapy or a combination of these). However, it is this subset of patients which is more likely to be identified and managed timely, possibly alleviating the premature mortality associated with hypopituitarism. What is more challenging is the recognition of hypopituitarism in less common settings, which may be either due to direct involvement of the pituitary (infection, traumatic brain injury, or infiltrative causes) or indirectly as a consequence of the primary process (thalassemia, vasculotoxic snakebite, subarachnoid hemorrhage). These entities are often under-recognised, and increased awareness can help in greater recognition of the problem burden. Further, pituitary insufficiency in most of these settings is dynamic, which may progress, or rarely, show recovery of function. This renders complexity to the problem, but makes it even more imperative to suspect, screen and appropriately manage patients with less common causes of hypopituitarism.

Central diabetes insipidus with anti-rabphilin-3A antibody positivity causing hypovolemic shock after resection of tumorous lesions in the pelvic cavity

A 36-year-old female was pointed out to have liver enzyme elevation by routine health checkup. Subsequent contrast-enhanced CT scan identified gigantic uterine fibroids and retroperitoneal tumor. She was referred to the gynecologist at JA Toride Medical Center and planned to undergo a uterus enucleation and biopsy of the retroperitoneal tumor. The surgery was conducted without any troubles. After the surgery, the patient presented polyuria with urine volume 10-20 L a day and developed hypovolemic shock. Laboratory test revealed hypotonic urine and hypernatremia. Arginine vasopressin (AVP) loading test suggested shortage of endogenous vasopressin. Since the subcutaneous administration of AVP was not sufficient to control the urine volume, continuous intravenous infusion of AVP was initiated. After achieving hemodynamic stability, the treatment was switched to oral desmopressin. MRI finding indicated attenuation of high signal in posterior pituitary in T1 weighted image while neither enlargement of pituitary nor thickening of pituitary stalk was indicated by enhanced MRI. Hypertonic salt solution test indicated no responsive elevation of AVP, confirming the diagnosis of central diabetes insipidus (CDI). Her anterior pituitary function was preserved. Only anti-rabphilin-3A antibody was found positive in the serum of the patient, while other secondary causes for CDI were denied serologically and radiologically. Hence, lymphocytic infundibuloneurohypophysitis　(LINH) was suspected as the final diagnosis. Hormonal replacement therapy by nasal desmopressin was continued and the patient managed to control her urine volume. In cases of CDI considered idiopathic with conventional examinations, anti-rabphilin-3A antibody may be a clue for determining the cause as LINH.

Preoperative differentiation of hypophysitis and pituitary adenomas using a novel clinicoradiologic scoring system

PURPOSE

Hypophysitis can clinically and radiologically mimic other nonfunctioning masses of the sella turcica, complicating preoperative diagnosis. While sellar masses may be treated surgically, hypophysitis is often treated medically, so differentiating between them facilitates optimal management. The objective of our study was to develop a scoring system for the preoperative diagnosis of hypophysitis.

METHODS

A thorough literature review identified published hypophysitis cases, which were compared to a retrospective group of non-functioning pituitary adenomas (NFA) from our institution. A preoperative hypophysitis scoring system was developed and internally validated.

RESULTS

Fifty-six pathologically confirmed hypophysitis cases were identified in the literature. After excluding individual cases with missing values, 18 hypophysitis cases were compared to an age- and sex-matched control group of 56 NFAs. Diabetes insipidus (DI) (p < 0.001), infundibular thickening (p < 0.001), absence of cavernous sinus invasion (CSI) (p < 0.001), relation to pregnancy (p = 0.002), and absence of visual symptoms (p = 0.007) were significantly associated with hypophysitis. Stepwise logistic regression identified DI and infundibular thickening as positive predictors of hypophysitis. CSI and visual symptoms were negative predictors. A 6-point hypophysitis-risk scoring system was derived: + 2 for DI, + 2 for absence of CSI, + 1 for infundibular thickening, + 1 for absence of visual symptoms. Scores ≥ 3 supported a diagnosis of hypophysitis (AUC 0.96, sensitivity 100%, specificity 75%). The scoring system identified 100% of hypophysitis cases at our institution with an estimated 24.7% false-positive rate.

CONCLUSIONS

The proposed scoring system may aid preoperative diagnosis of hypophysitis, preventing unnecessary surgery in these patients.

Hypophysitis

OBJECTIVE

Hypophysitis is considered a rare inflammatory disease of the pituitary gland. For a long time, primary autoimmune hypophysitis has stood out as the most relevant type of hypophysitis. However, with the advent of immunotherapy for the treatment of malignancies and identification of hypophysitis as an immune-related adverse event, hypophysitis has garnered increasing interest and recognition. Therefore, awareness, early recognition, and appropriate management are becoming important as the indication for immunomodulatory therapies broaden.

METHODS

In this review, we discuss the epidemiology, diagnosis, and treatment of hypophysitis with a focus on recent data and highlight subtypes of particular interest while recognizing the gaps in knowledge that remain.

RESULTS

Regardless of cause, symptoms and signs of hypophysitis may be related to mass effect (headache and visual disturbance) and hormonal disruption that warrant prompt evaluation. In the vast majority of cases, a diagnosis of hypophysitis can be made presumptively in the appropriate clinical context with radiologic findings consistent with hypophysitis and after the exclusion of other causes.

CONCLUSION

Although subtle differences currently exist in management and outcome expectations between primary and secondary causes of hypophysitis, universally, treatment is aimed at symptom management and hormonal replacement therapy.

A 7-year-old boy with central diabetes insipidus presenting with thickened pituitary stalk and anti-rabphilin-3A antibody positivity

OBJECTIVES

A highly invasive pathological diagnosis is necessary to differentiate central diabetes insipidus (CDI) with a thickened pituitary stalk. Lymphocytic infundibulo-hypophysitis (LIH) due to autoimmune involvement of the pituitary stalk is a differentiating disease, and anti-rabphilin-3A antibody (Rab3A-Ab) positivity was recently reported.

CASE PRESENTATION

A 7-year-old boy was diagnosed with CDI after having polyuria for two months. He showed growth hormone deficiency with reduced growth rate. Brain magnetic resonance imaging (MRI) revealed a thickened pituitary stalk. The placental alkaline phosphatase level of the cerebrospinal fluid, tumor marker for germ cell tumors, was below the level of sensitivity. No skin or bone findings suggestive of Langerhans cell histiocytosis were detected. Eight months after CDI onset, Rab3A-Ab was positive, and MRI showed shrinking of the thickened pituitary stalk, leading to the diagnosis with LIH.

CONCLUSIONS

Rab3A-Ab is a useful adjunctive diagnostic tool for childhood-onset LIH.

Infantile-Onset Isolated Neurohypophyseal Langerhans Cell Histiocytosis with Central Diabetes Insipidus: A Case Report

Central diabetes insipidus (CDI) is a rare disease in children and has a variety of etiologies. The major causes of CDI with pituitary stalk thickening (PST) are germinoma, Langerhans cell histiocytosis (LCH), and Lymphocytic infundibulo-neurohypophysitis, which are difficult to differentiate by imaging and require pathological diagnosis. We report a case of infantile-onset isolated neurohypophyseal LCH diagnosed by pathological findings. A 2-year-old girl presented with polydipsia and polyuria. CDI was diagnosed and treatment with oral desmopressin was initiated. Magnetic resonance imaging (MRI) of the head showed PST and absence of high-signal intensity of posterior pituitary on T1-weighted images. Follow-up MRI scans showed that the tumor mass was gradually increasing and extending posteriorly toward the area near the mamillary body. Simultaneously, anterior pituitary dysfunction was observed. She underwent a biopsy of the PST and LCH was diagnosed by immunohistochemical analysis. DNA analysis showed no BRAF V600E mutation. Monotherapy with 2-Chlorodeoxyadenosine reduced the tumor size but did not improve pituitary function. Isolated neurohypophyseal LCH should be considered in infantile-onset cases of CDI with PST. 2-CdA treatment resulted in rapid PST shrinkage. Further cases are needed to determine whether early diagnosis and treatment can prevent anterior pituitary dysfunction.

Paraneoplastic autoimmune hypophysitis: An emerging concept

Pituitary autoimmunity is one of the principal causes of hypopituitarism. Additionally, hypophysitis is one of the immune-related adverse events associated with immunotherapy. Recent case-oriented research has revealed a novel type of autoimmune hypophysitis, anti-PIT-1 hypophysitis, related to isolated adrenocorticotropic hormone (ACTH) deficiency and immune checkpoint inhibitor-related hypophysitis, as a form of paraneoplastic syndrome. Under these conditions, the ectopic expression of pituitary antigens present in tumors evokes a breakdown of immune tolerance, resulting in the production of autoantibodies and autoreactive cytotoxic T cells that specifically harm pituitary cells. Consequently, an innovative clinical entity of paraneoplastic autoimmune hypophysitis has been purported. This novel concept and its underlying mechanisms provide clues for understanding the pathogenesis of autoimmune pituitary diseases and can be applied to other autoimmune diseases. This review discusses the etiology of paraneoplastic autoimmune hypophysitis and its future.

Clinical features and difficulty in diagnosis of Langerhans cell histiocytosis in the hypothalamic-pituitary region

Langerhans cell histiocytosis (LCH) is a multi-organ disorder that rarely involves the hypothalamic-pituitary region (HPR). HPR-LCH presents with severe progressive pituitary dysfunction and its prognosis is poor. The definitive diagnosis of LCH is considerably difficult and complicated owing to the occurrence of several diseases with similar manifestations in the HPR and its location in the deepest portion of the anterior skull base, in close proximity to important normal structures, severely limiting the size of the biopsy specimen. Chemotherapy is the established treatment modality for LCH; hence, timely and accurate diagnosis of LCH is essential for early therapeutic intervention. We retrospectively reviewed clinical features and biopsy procedures in four patients with HPR-LCH (all female, 28-44 years old) from 2009 to 2020. Maximum diameter of supra-sellar lesions was 23-35 mm and 2 cases had skip lesions. All patients demonstrated central diabetes insipidus, hyper-prolactinemia, and severe anterior pituitary dysfunction. Two of the patients had progressive disease. Furthermore, four patients presented body weight gain, two visual disturbance, and two impaired consciousness. The duration from onset to diagnosis of LCH was 3 to 10 (average 7.25) years. In total, eight operations were performed until final diagnosis. The percentage of correct diagnosis by biopsy was 50% (4/8). Clinical features of HPR-LCH are very similar to those of other HPR diseases, and their symptoms are progressive and irreversible. Clinicians should consider repeated biopsy with a more aggressive approach if the lesion is refractory to steroid therapy, in order to ensure accurate diagnosis and appropriate treatment.

Lymphocytic panhypophysitis and anti-rabphilin-3A antibody with pulmonary sarcoidosis

PURPOSE

To explore the clinical significance of anti-rabphillin-3A antibody for the differential diagnosis of lymphocytic panhypophysitis.

METHODS AND RESULTS

A 58-year-old Japanese man developed uveitis of unknown cause in 2017. In 2019, he became aware of polyuria. In August 2020, he noticed transient diplopia and was diagnosed with right abducens nerve palsy. At the same time, he complained of fatigue and loss of appetite. Head magnetic resonance imaging demonstrated enlargement of the pituitary stalk and pituitary gland, corresponding to hypophysitis. Hormone stimulation tests showed blunted responses with respect to all anterior pituitary hormones. Central diabetes insipidus was diagnosed on the basis of a hypertonic saline loading test. Taking these findings together, a diagnosis of panhypopituitarism was made. Computed tomography showed enlargement of hilar lymph nodes. Biopsies of the hilar lymph nodes revealed non-caseating epithelioid cell granulomas that were consistent with sarcoidosis. Biopsy of the anterior pituitary revealed mild lymphocyte infiltration in the absence of IgG4-positive cells, non-caseating granulomas, or neoplasia. Western blotting revealed the presence of anti-rabphilin-3A antibody, supporting a diagnosis of lymphocytic panhypophysitis. Because the patient had no visual impairment or severe uveitis, we continued physiological hormone replacement therapy and topical steroid therapy for the uveitis.

CONCLUSION

To the best of our knowledge, this is the first case of anti-rabphilin 3A antibody positive lymphocytic panhypophysitis comorbid with sarcoidosis, diagnosed by both pituitary and hilar lymph node biopsy. The utility of anti-rabphilin-3A antibody for the differential diagnosis of hypophysitis like this case should be clarified with further case studies.

Immune Checkpoint Inhibitor-Induced Central Diabetes Insipidus: Looking for the Needle in the Haystack or a Very Rare Side-Effect to Promptly Diagnose?

Immune checkpoint inhibitors have improved the survival in patients affected by an increasing number of malignancies, but they may also trigger various autoimmune side-effects, including endocrinopathies. Very rarely, immune checkpoint inhibitors have been reported to cause central diabetes insipidus. However, with their expanding use, the likelihood that oncologists will face this endocrine adverse event is expected to increase. By reviewing the limited literature on central diabetes insipidus induced by immune checkpoint inhibitors, some inconsistencies emerge in the diagnosis and the management of patients presenting with this toxicity, together with difficulties related to classifying its severity. Until now, specific guidelines on the management of central diabetes insipidus induced by immune checkpoint inhibitors are lacking. In clinical practice, endocrinological consultation may relieve medical oncologists from difficulties in treating this side-effect; oncologists, however, remain responsible for its early diagnose and the management of the causative drugs. To this aim, some practical suggestions are advised for the multidisciplinary management of cancer patients presenting with central diabetes insipidus induced by immune checkpoint inhibitors.

Studies on anti-rabphilin-3A antibodies in 15 consecutive patients presenting with central diabetes insipidus at a single referral center

Central diabetes insipidus (CDI) is a rare condition caused by various underlying diseases including inflammatory and autoimmune diseases, and neoplasms. Obtaining an accurate definitive diagnosis of the underlying cause of CDI is difficult. Recently, anti-rabphilin-3A antibodies were demonstrated to be a highly sensitive and specific marker of lymphocytic infundibuloneurohypophysitis (LINH). Here, we report a detailed case series, and evaluated the significance of anti-rabphilin-3A antibodies in differentiating the etiologies of CDI. A prospective analysis was conducted in 15 consecutive patients with CDI from 2013 to 2020 at a single referral center. Anti-rabphilin-3A antibodies were measured and the relationship between antibody positivity and the clinical/histopathological diagnoses was evaluated. Among 15 CDI patients, the positive anti-rabphilin-3A antibodies were found in 4 of 5 LINH cases, 3 of 4 lymphocytic panhypophysitis (LPH) cases, one of 2 sarcoidosis cases, and one intracranial germinoma case, respectively. Two Rathke cleft cyst cases and one craniopharyngioma case were negative. This is the first report of anti-rabphilin-3A antibodies positivity in CDI patients with biopsy-proven LPH. Measurement of anti-rabphilin-3A antibodies may be valuable for differentiating CDI etiologies.

Ketoacidosis, Hypertriglyceridemia and Acute Pancreatitis Induced by Soft Drink Polydipsia in a Patient with Occult Central Diabetes Insipidus

A 21-year-old Japanese man without known diabetes mellitus had abdominal pain. The diagnosis was ketoacidosis and hypertriglyceridemia-induced acute pancreatitis. He had polydipsia and polyuria and had habitually drunk several soft drinks every day for two years. After hospitalization, despite adequate liquid intake, dehydration remained with hypotonic polyuria. Further examinations revealed the coexistence of central diabetes insipidus (CDI), possibly caused by lymphocytic infundibulo-neurohypophysitis, based on anti-rabphilin-3A antibody positivity. Although CDI had been undiagnosed for two years, over-consumption of sugar-rich soft drinks to ease thirst caused ketoacidosis, hypertriglyceridemia, and acute pancreatitis. There are no previous reports of this three-part combination of symptoms caused by CDI.

Molecular and Genetic Immune Biomarkers of Primary and Immune-Therapy Induced Hypophysitis: From Laboratories to the Clinical Practice

Hypophysitis is a rare and potentially life-threatening disease, characterized by an elevated risk of complications, such as the occurrence of acute central hypoadrenalism, persistent hypopituitarism, or the extension of the inflammatory process to the neighboring neurological structures. In recent years, a large number of cases has been described. The diagnosis of hypophysitis is complex because it is based on clinical and radiological criteria. Due to this, the integration of molecular and genetic biomarkers can help physicians in the diagnosis of hypophysitis and play a role in predicting disease outcome. In this paper, we review current knowledge about molecular and genetic biomarkers of hypophysitis with the aim of suggesting a possible integration of these biomarkers in clinical practice.

Recent insights into the pathogenesis of autoimmune hypophysitis

INTRODUCTION

Hypophysitis is an inflammation of the pituitary gland and a rare case of hypopituitarism. Despite the expanding spectrum of histological variants and causative agents, its pathogenesis is far to be fully understood. The present review is focused on recent evidence concerning the pathogenesis of autoimmune hypophysitis by searching through online databases like MEDLINE and Scopus up to May 2021.

AREAS COVERED

Hypophysitis frequently develops in the context of a strong autoimmune background, including a wide spectrum of subtypes ranging from the commonest form of lymphocytic hypophysitis to the newly described and less common IgG4-, anti-PIT-1, and ICI-induced forms. A peculiar combination of genetic predisposition, pituitary damage and immunological setting represents the pathogenetic basis of autoimmune hypophysitis, which is characterized by diffuse infiltration of the gland by lymphocytes and variable degrees of fibrosis followed by pituitary cell destruction. Anti-pituitary antibodies (APA) have been described in sera from patients suffering from autoimmune hypophysitis, though their pathophysiological significance remains largely unknown and their diagnostic value limited.

EXPERT OPINION

In recent years hypophysitis has gained interest due to the increased number of new diagnoses and the recognition of novel subtypes. Further studies could lead to improvements in biochemical/immunological diagnosis and targeted treatments.

Markers of humoral and cell-mediated immune response in primary autoimmune hypophysitis: a pilot study

INTRODUCTION

Primary autoimmune hypophysitis (PAHs) is a rare inflammatory disease of the pituitary gland. Although largely investigated, the pathogenesis of PAH is not completely clarified. We aimed to investigate the immune response in PAHs.

MATERIAL AND METHODS

Serum anti-pituitary and anti-hypothalamus antibodies (respectively APAs and AHAs) were investigated though an indirect immunofluorescence on monkey hypophysis and hypothalamus slides, serum cytokines though an array membrane and cell-mediated immunity though the white blood cells count.

RESULTS

Nineteen PAH cases entered the study. APA or AHA were identified in all cases. APA were detected in 13 patients (68.4%) and AHA in 13 patients (68.4%). Ten patients (52.6%) were simultaneously positive for both APA and AHA. The prevalence of APAs and AHAs was higher as compared to those observed in 50 health controls (respectively 14% p < 0.001 and 24% p = 0.004) and in 100 not-secreting pituitary adenoma (NFPAs) (respectively 22% p = 0.002 and 8% p < 0.001). Similarly, the prevalence of simultaneous positivity for APA and AHA (52.9%) was higher as compared to the those detected in patients affected by NFPAs (0%; p < 0.001) and in health controls (16% p = 0.002). No differences were identified between PAHs and controls at qualitative and quantitative analysis of serum cytokines and white blood cells count.

CONCLUSIONS

This study suggest that APA and AHA may be detected in an high percentage of PAH cases and that their simultaneous identification may be useful for the differential diagnosis between PAH and NFPAs, in an appropriate clinical context.

Central diabetes insipidus developing in a 6-year-old patient 4 years after the remission of unifocal bone Langerhans cell histiocytosis

A six-year-old boy was referred with a one-and-a-half months history of polyuria and polydipsia. At the age of two, he had a single lytic bone lesion in his femoral head, diagnosed as Langerhans cell histiocytosis (LCH) by biopsy at another hospital. As no other affected organs were detected and the affected bone lesion was self-limited, he was not followed up afterward and was doing well. He was diagnosed with diabetes insipidus (DI) by confirming hypernatremia (Na: 148 mEq/l) with hyperosmolar serum (s-Osm 298 mOSM/kg) and inappropriately diluted urine (u-Osm 205 mOSM/kg). His polyuria and polydipsia improved dramatically using the perioral diuretic hormone, and other pituitary functions were not impaired. Magnetic resonance imaging revealed an enlarged pituitary stalk. Sensitive and specific biomarkers of germ cell tumors, including alpha-fetoprotein, placental alkaline phosphatase, and β-hCG in the cerebrospinal fluid, were not detected, indicating relapse of LCH. Genetic analysis revealed a BRAF V600E mutation in the primary bone lesion. We recommend systematic follow-up of patients with a history of LCH, even non-CNS single-system single-site disease, especially with BRAF V600E mutation.

Diagnosis and management of diabetes insipidus for the internist: an update

Diabetes insipidus is a disorder characterized by excretion of large amounts of hypotonic urine. Four entities have to be differentiated: central diabetes insipidus resulting from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, nephrogenic diabetes insipidus resulting from resistance to AVP in the kidneys, gestational diabetes insipidus resulting from an increase in placental vasopressinase and finally primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Distinguishing between the different types of diabetes insipidus can be challenging. A detailed medical history, physical examination and imaging studies are needed to detect the aetiology of diabetes insipidus. Differentiation between the various forms of hypotonic polyuria is then done by the classical water deprivation test or the more recently developed hypertonic saline or arginine stimulation together with copeptin (or AVP) measurement. In patients with idiopathic central DI, a close follow-up is needed since central DI can be the first sign of an underlying pathology. Treatment of diabetes insipidus or primary polydipsia depends on the underlying aetiology and differs in central diabetes insipidus, nephrogenic diabetes insipidus and primary polydipsia. This review will discuss issues and newest developments in diagnosis, differential diagnosis and treatment, with a focus on central diabetes insipidus.

Anti-pituitary antibodies and susceptible human leukocyte antigen alleles as predictive biomarkers for pituitary dysfunction induced by immune checkpoint inhibitors

BACKGROUND

Pituitary dysfunction is a life-threatening immune-related adverse event (irAE) induced by immune checkpoint inhibitors (ICIs). To date, it is not possible to identify patients who may develop pituitary irAEs prior to ICI treatment. The aim of this study was to characterize the predisposition for ICI-induced pituitary irAEs by analyzing anti-pituitary antibodies (APAs) and human leukocyte antigens (HLAs).

METHODS

In this case-control study, APAs and HLA alleles were analyzed in 62 patients (17 who developed ICI-induced isolated adrenocorticotropic hormone deficiency (ICI-IAD), 5 who developed ICI-induced hypophysitis (ICI-H) and 40 who did not develop pituitary irAEs) treated with ICIs between November 2, 2015, and March 31, 2020, at Nagoya University Hospital. The main outcome measures in this study were the association between the development of pituitary irAEs with APAs at baseline and after treatment and HLA alleles.

RESULTS

Eleven of 17 (64.7%) patients who developed ICI-IAD had APAs at baseline, whereas APAs were positive only in 1 of 40 (2.5%) control patients. Although APAs were negative at baseline in all patients who developed ICI-H, they had become positive before the onset of ICI-H in 3 of 4 patients several weeks after ipilimumab administration. At the onset of ICI-IAD and ICI-H, APAs were positive in 15 of 17 (88.2%) and 4 of 5 (80%) patients, respectively. The prevalence of HLA-Cw12, HLA-DR15, HLA-DQ7, and HLA-DPw9 was significantly higher in patients with ICI-IAD, whereas that of HLA-Cw12 and HLA-DR15 was significantly higher in patients with ICI-H than in controls.

CONCLUSIONS

This study showed distinct and overlapped patterns of APAs and HLA alleles between ICI-IAD and ICI-H. Our findings also showed that positive APAs at baseline and after treatment, together with susceptible HLA alleles, could become predictive biomarkers for ICI-IAD and ICI-H, respectively.

TRIAL REGISTRATION NUMBER

UMIN000019024.

Vasopressin-Dependent Disorders: What Is New in Children?

Arginine vasopressin (AVP)-mediated osmoregulatory disorders, such as diabetes insipidus (DI) and syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are common in the differential diagnosis for children with hypo- and hypernatremia and require timely recognition and treatment. DI is caused by a failure to concentrate urine secondary to impaired production of or response to AVP, resulting in hypernatremia. Newer methods of diagnosing DI include measuring copeptin levels; copeptin is AVP's chaperone protein and serves as a surrogate biomarker of AVP secretion. Intraoperative copeptin levels may also help predict the risk for developing DI after neurosurgical procedures. Copeptin levels hold diagnostic promise in other pediatric conditions, too. Recently, expanded genotype and phenotype correlations in inherited DI disorders have been described and may better predict the clinical course in affected children and infants. Similarly, newer formulations of synthetic AVP may improve pediatric DI treatment. In contrast to DI, SIADH, characterized by inappropriate AVP secretion, commonly leads to severe hyponatremia. Contemporary methods aid clinicians in distinguishing SIADH from other hyponatremic conditions, particularly cerebral salt wasting. Further research on the efficacy of therapies for pediatric SIADH is needed, although some adult treatments hold promise for pediatrics. Lastly, expansion of home point-of-care sodium testing may transform management of SIADH and DI in children. In this article, we review recent developments in the understanding of pathophysiology, diagnostic workup, and treatment of better outcomes and quality of life for children with these challenging disorders.

Human pituitary development and application of iPSCs for pituitary disease

The pituitary plays a pivotal role in maintaining systemic homeostasis by secreting several hormones. During fetal development, the pituitary develops from the oral ectoderm in contact with the adjacent hypothalamus. This process is regulated by the fine-tuned expression of transcription and growth factors. Impairments of this process result in congenital pituitary hypoplasia leading to dysfunction of the pituitary. Although animal models such as knockout mice have helped to clarify these underlying mechanisms, the developmental processes of the human pituitary gland and the mechanisms of human pituitary disorders have not been fully understood. This is because, at least in part, of the lack of a human pituitary developmental model. Recently, methods for in vitro induction of the pituitary gland from human pluripotent stem cells were developed. These models can be utilized not only for regenerative medicine but also for human pituitary studies on developmental biology and for modeling of pituitary disorders, such as hypopituitarism and pituitary tumors. In this review, we provide an overview of recent progress in the applications of pluripotent stem cells for pituitary research and discuss further perspectives for pituitary studies.

Hypothalamitis: A Novel Autoimmune Endocrine Disease. A Literature Review and Case Report

CONTEXT

The relationship between the endocrine system and autoimmunity has been recognized for a long time and one of the best examples of autoimmune endocrine disease is autoimmune hypophysitis. A better understanding of autoimmune mechanisms and radiological, biochemical, and immunological developments has given rise to the definition of new autoimmune disorders including autoimmunity-related hypothalamic-pituitary disorders. However, whether hypothalamitis may occur as a distinct entity is still a matter of debate.

EVIDENCE ACQUISITION

Here we describe a 35-year-old woman with growing suprasellar mass, partial empty sella, central diabetes insipidus, hypopituitarism, and hyperprolactinemia.

EVIDENCE SYNTHESIS

Histopathologic examination of surgically removed suprasellar mass revealed lymphocytic infiltrate suggestive of an autoimmune disease with hypothalamic involvement. The presence of antihypothalamus antibodies to arginine vasopressin (AVP)-secreting cells (AVPcAb) at high titers and the absence of antipituitary antibodies suggested the diagnosis of isolated hypothalamitis. Some similar conditions have sometimes been reported in the literature but the simultaneous double finding of lymphocytic infiltrate and the presence of AVPcAb so far has never been reported.

CONCLUSIONS

We think that the hypothalamitis can be considered a new isolated autoimmune disease affecting the hypothalamus while the lymphocytic infundibuloneurohypophysitis can be a consequence of hypothalamitis with subsequent autoimmune involvement of the pituitary. To our knowledge this is the first observation of autoimmune hypothalamic involvement with central diabetes insipidus, partial empty sella, antihypothalamic antibodies and hypopituitarism.

Lymphocytic infundibuloneurohypophysitis with positive anti-rabphilin-3A antibodies nine years post-onset of central diabetes insipidus

Childhood-onset lymphocytic infundibuloneurohypophysitis (LINH) due to infiltration of autoimmune lymphocyte in the neurohypophysis is rarely reported. Its definitive diagnosis requires a pituitary biopsy, which is an invasive procedure. Recently, anti-rabphilin-3A antibody has been reported as a potential diagnostic marker for LINH in adults; however, only a few cases have been reported in children. Here, we present a case of childhood-onset LINH in a 10-yr-old boy identified as anti-rabphilin-3A antibody positive during chronic phase, 9 yr post-onset of central diabetes insipidus (CDI). T1-weighted magnetic resonance imaging (MRI) revealed pituitary stalk thickening and absence of posterior pituitary bright signal spot, and the hormonal responses of the adenohypophysis to GHRH, TRH, CRH, and LHRH revealed no abnormalities during the first admission. MRI at 5 mo post-onset indicated reduced stalk swelling; however, replacement treatment with intranasal desmopressin was continued to counter unimproved CDI. Additionally, GH replacement therapy was also initiated to counter its deficiency. Pituitary re-enlargement was not observed in the subsequent routine MRI, and no increase was observed in the levels of tumor markers during follow-up, which was considered clinically consistent with LINH. Our case study suggests that anti-rabphilin-3A antibody may be considered as a useful diagnostic marker for LINH in children.

Autoimmune diabetes insipidus

Once central diabetes insipidus (CDI) has been diagnosed, every effort should be made to reveal its underlying cause. Autoimmune CDI should be considered in the differential diagnosis of idiopathic CDI and also of mass lesions of the sella region. An autoimmune etiology of CDI was first suggested in 1983 by the detection of autoantibodies to hypothalamic vasopressin-producing cells (AVPcAb) in adults and also in children with the disease, using the indirect immunofluorescence test. The major autoantigen for autoimmune CDI has now been recognized as rabphilin-3A, a protein of secretory vesicles of the neurohypophyseal system. The detection of autoantibodies to rabphilin-3A by Western blotting or of AVPcAb provides strong evidence for the diagnosis of autoimmune CDI. Autoimmune CDI is recognized mostly in patients who had also been diagnosed with endocrine autoimmune disorders. The radiological and morphological correlate with autoimmune DI is lymphocytic infundibuloneurohypophysitis (LINH) as detected by magnetic resonance imaging and biopsies that show massive infiltration of the posterior pituitary and the infundibulum with lymphocytes and some plasma cells, and fibrosis in the later stages of the disease. LINH may be associated with lymphocytic anterior hypophysitis. Both may either appear spontaneously or on treatment with immune checkpoint inhibitors.

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.

Endocrine adverse events related with immune checkpoint inhibitors: an update for clinicians

Designated as scientific breakthrough of current decade, immune checkpoint inhibitors attenuate the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and the programmed cell death 1 (PD-1)/ligand 1 (PD-L1) pathways, depriving cancer cells of a key strategy of evasion from immunosurveillance. The reinvigoration of immune response translates into clinical success, inevitably entwined with a novel constellation of immune-related adverse events. The present review dissects the endocrine immune-related adverse events, emphasizing their unique profile featured by unpredictable onset, irreversibility, nonspecific symptoms, wide clinical spectrum and sophisticated diagnostic work-up. Guidelines advocate individualized decision-making process guided by clinicians' judgement. Future perspective should be governed by five principles - prevention, anticipation, detection, treatment, monitoring - aiming to gain the optimal profit diminishing immunotoxicity.

Hypophysitis (Including IgG4 and Immunotherapy)

Hypophysitis is characterized by inflammation of the pituitary gland that can be primary (PH) or secondary (SH) to other diseases or following drug administration. It may also be classified according to anatomical and histopathological criteria, leading to variable degrees of hypopituitarism and/or compressive symptoms to nearby structures. There has recently been an increase in the number of hypophysitis cases, raising the interest on the spectrum of its pathogenesis, clinical, biochemical/endocrinological, and imaging features. However, the use of conventional biomarkers, including currently utilized pituitary autoantibodies, has relatively limited diagnostic accuracy. Lymphocytic hypophysitis (LH) is the commonest cause of PH, whereas IgG4-related hypophysitis is increasingly being recognized. Histiocytosis and granulomatous diseases are the most frequent causes of SH, although infections and lymphoma have also been reported. The increasing use of immune checkpoint inhibitors in oncology is associated with a high incidence of hypophysitis, providing further understanding of its pathogenesis. Hypophysitis can occur silently and be easily missed, potentially leading to substantial morbidity or mortality due to adrenal insufficiency, requiring a high index of clinical suspicion and timely initiation of appropriate treatment. In most cases of LH or drug-induced hypophysitis, active surveillance along with replacement of established hormonal deficiencies is needed. In the presence of compressive and/or evolving symptoms, treatment with glucocorticoids either alone or in combination with other immunosuppressive agents can be used. Surgical decompression is reserved for nonresponsive cases with threatened vital structures. Timely diagnosis and intervention are important to minimize disease-related morbidity and mortality. We aimed to review current concepts and recent developments in the pathogenesis, diagnosis, and management of hypophysitis.

Diabetes insipidus

Diabetes insipidus (DI) is a disorder characterized by excretion of large amounts of hypotonic urine. Central DI results from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, whereas nephrogenic DI results from resistance to AVP in the kidneys. Central and nephrogenic DI are usually acquired, but genetic causes must be evaluated, especially if symptoms occur in early childhood. Central or nephrogenic DI must be differentiated from primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Primary polydipsia is most common in psychiatric patients and health enthusiasts but the polydipsia in a small subgroup of patients seems to be due to an abnormally low thirst threshold, a condition termed dipsogenic DI. Distinguishing between the different types of DI can be challenging and is done either by a water deprivation test or by hypertonic saline stimulation together with copeptin (or AVP) measurement. Furthermore, a detailed medical history, physical examination and imaging studies are needed to ensure an accurate DI diagnosis. Treatment of DI or primary polydipsia depends on the underlying aetiology and differs in central DI, nephrogenic DI and primary polydipsia.

Hypophysitis in the era of immune checkpoint inhibitors and immunoglobulin G4-related disease

INTRODUCTION

Hypophysitis is a rare disorder, defined as inflammation of the pituitary gland that may result in pituitary enlargement and varying anterior and posterior pituitary hormonal deficits. It involves different histopathological subtypes and variable etiologies, with considerable overlap between classification systems. Histopathology is the gold standard diagnostic approach.

AREAS COVERED

In this article, we will review the major histopathological subtypes of hypophysitis with a special focus on immunoglobulin G4 (IgG4)-related hypophysitis and immune checkpoint inhibitor-induced hypophysitis, given their recent appearance and increasing incidence. We will summarize the similarities and differences between the different subtypes as it relates to epidemiology, pathogenesis, presentation, diagnosis, and management.

EXPERT OPINION

Hypophysitis is a heterogeneous and wide term used to describe different, possibly distinct diseases often with poorly understood pathogenesis. It involves a wide range of subtypes with certain differences in incidence rates, pathogenesis, and management. Management usually focuses on relieving the mass effect symptoms and replacing the deficient pituitary hormones. Spontaneous recovery is possible but recurrence is not uncommon.

New causes of hypophysitis

Hypophysitis is a rare entity characterized by inflammation of the pituitary gland and its stalk that can cause hypopituitarism and/or mass effect. Etiology can be categorized as primary or secondary to systemic disease, but may also be classified according to anatomical and hispathological criteria. Newly recognized causes of hypophysits have been described, mainly secondary to immunomodulatory medications and IgG4-related disease. Diagnosis is based on clinical, laboratory and imaging data, whereas pituitary biopsy, though rarely indicated, may provide a definitive histological diagnosis. For the clinician, obtaining a broad clinical and drug history, and performing a thorough physical examination is essential. Management of hypophysitis includes hormone replacement therapy if hypopituitarism is present and control of the consequences of the inflammatory pituitary mass (e.g. compression of the optic chiasm) using high-dose glucocorticoids, whereas pituitary surgery is reserved for those unresponsive to medical therapy and/or have progressive disease. However, there remains an unmet need for controlled studies to inform clinical practice.

Hypophysitis Outcome and Factors Predicting Responsiveness to Glucocorticoid Therapy: A Prospective and Double-Arm Study

CONTEXT

Primary autoimmune hypophysitis (PAH) evolves in most untreated cases in irreversible hypopituitarism. PAH outcome, instead, after immunosuppressive treatment has not been completely clarified.

OBJECTIVE

To evaluate hypophysitis and pituitary function outcomes.

DESIGN

A prospective, double-arm study with a 2-year follow-up.

SETTING

Referral center for pituitary disease.

PATIENTS

Twenty PAH cases.

INTERVENTIONS

Oral prednisone 50 mg/d or conservative strategy by observation.

MAIN OUTCOME MEASURES

Primary endpoint was the improvement/stabilization/worsening of PAH from baseline to a 2-year visit. Secondary endpoint was the improvement/stabilization/worsening of pituitary function from baseline to a 2-year visit.

RESULTS

Twelve patients (57.1%) were treated with a glucocorticoid-immunosuppressive therapy, and eight patients (42.9%) were observed. At the 2-year visit, PAH improvement/recovery occurred in eight immunosuppressive-treated (66.7%) patients and in two untreated patients (25%). PAH worsened in three untreated patients (37.5%) and was considered stable in four immunosuppressive-treated (33.3%) and three untreated patients (37.5%). Improvement/recovery of pituitary function occurred more frequently in immunosuppressive-treated patients (58.3%) compared with untreated ones (25%; P = 0.04). Responsiveness to immunosuppressive treatment is correlated with antipituitary antibody presence (P = 0.01), occurrence of diabetes insipidus at PAH diagnosis (P = 0.01), absence of the physiological neuropituitary "bright spot" on T1-weighed images (P = 0.01), and pituitary stalk at optical chiasm larger than 3.9 mm (area under the curve: 0.97, sensibility: 100%, specificity: 100%; P = 0.04). On the other hand, we failed to identify factors predicting the outcome, among untreated patients.

CONCLUSIONS

Glucocorticoid treatment of hypophysitis improves pituitary secretion and should be encouraged in accordance with the evaluation of endocrine-, immunological-, and morphological-predictive markers.

The Paraventricular Nucleus of the Hypothalamus: Development, Function, and Human Diseases

The paraventricular nucleus of the hypothalamus (PVH), located in the ventral diencephalon adjacent to the third ventricle, is a highly conserved brain region present in species from zebrafish to humans. The PVH is composed of three main types of neurons, magnocellular, parvocellular, and long-projecting neurons, which play imperative roles in the regulation of energy balance and various endocrinological activities. In this review, we focus mainly on recent findings about the early development of the hypothalamus and the PVH, the functions of the PVH in the modulation of energy homeostasis and in the hypothalamus-pituitary system, and human diseases associated with the PVH, such as obesity, short stature, hypertension, and diabetes insipidus. Thus, the investigations of the PVH will benefit not only understanding of the development of the central nervous system but also the etiology of and therapy for human diseases.

MECHANISMS IN ENDOCRINOLOGY: Hypophysitis: diagnosis and treatment

Hypophysitis is a rare condition characterised by inflammation of the pituitary gland, usually resulting in hypopituitarism and pituitary enlargement. Pituitary inflammation can occur as a primary hypophysitis (most commonly lymphocytic, granulomatous or xanthomatous disease) or as secondary hypophysitis (as a result of systemic diseases, immunotherapy or alternative sella-based pathologies). Hypophysitis can be classified using anatomical, histopathological and aetiological criteria. Non-invasive diagnosis of hypophysitis remains elusive, and the use of currently available serum anti-pituitary antibodies are limited by low sensitivity and specificity. Newer serum markers such as anti-rabphilin 3A are yet to show consistent diagnostic value and are not yet commercially available. Traditionally considered a very rare condition, the recent recognition of IgG4-related disease and hypophysitis as a consequence of use of immune modulatory therapy has resulted in increased understanding of the pathophysiology of hypophysitis. Modern imaging techniques, histological classification and immune profiling are improving the accuracy of the diagnosis of the patient with hypophysitis. The objective of this review is to bring readers up-to-date with current understanding of conditions presenting as hypophysitis, focussing on recent advances and areas for future development. We describe the presenting features, investigation and diagnostic approach of the patient with likely hypophysitis, including existing conventional techniques and those in the research/development arena. Hypophysitis usually results in acute and persistent pituitary hormone deficiency requiring long-term replacement. Management of hypophysitis includes control of the inflammatory pituitary mass using a variety of treatment strategies including surgery and medical therapy. Glucocorticoids remain the mainstay of medical treatment but other immunosuppressive agents (e.g. azathioprine, rituximab) show benefit in some cases, but there is a need for controlled studies to inform practice.

Manifestation of Central Diabetes Insipidus in a Patient with Thyroid Storm

We herein report a case of central diabetes insipidus complicated with thyroid storm. A middle-aged woman who was receiving treatment for Graves' disease suddenly complained of polydipsia, polyuria and general fatigue. Laboratory tests showed hyperthyroidism, hypernatremia, hypoosmolar urine and a decreased plasma vasopressin level. The occurrence of central diabetes insipidus with hyperthyroidism was revealed on the basis of pituitary magnetic resonance imaging, a water deprivation test and a desmopressin test. The clinical co-existence of diabetes insipidus and hyperthyroidism is very rare; however, the complication should be considered when hypernatremia and/or dehydration progress in patients with Graves's disease as a common autoimmune-related etiology.

Critical role of rabphilin-3A in the pathophysiology of experimental lymphocytic neurohypophysitis

Autoimmune hypophysitis (AH) is thought to be an autoimmune disease characterized by lymphocytic infiltration of the pituitary gland. Among AH pathologies, lymphocytic infundibulo-neurohypophysitis (LINH) involves infiltration of the neurohypophysis and/or the hypothalamic infundibulum, causing central diabetes insipidus resulting from insufficiency of arginine vasopressin secretion. The pathophysiological and pathogenetic mechanisms underlying LINH are largely unknown. Clinically, differentiating LINH from other pituitary diseases accompanied by mass lesions, including tumours, has often been difficult, because of similar clinical manifestations. We recently reported that rabphilin-3A is an autoantigen and that anti-rabphilin-3A antibodies constitute a possible diagnostic marker for LINH. However, the involvement of rabphilin-3A in the pathogenesis of LINH remains to be elucidated. This study was undertaken to explore the role of rabphilin-3A in lymphocytic neurohypophysitis and to investigate the mechanism. We found that immunization of mice with rabphilin-3A led to neurohypophysitis. Lymphocytic infiltration was observed in the neurohypophysis and supraoptic nucleus 1 month after the first immunization. Mice immunized with rabphilin-3A showed an increase in the volume of urine that was hypotonic as compared with control mice. Administration of a cocktail of monoclonal anti-rabphilin-3A antibodies did not induce neurohypophysitis. However, abatacept, which is a chimeric protein that suppresses T-cell activation, decreased the number of T cells specific for rabphilin-3A in peripheral blood mononuclear cells (PBMCs). It ameliorated lymphocytic infiltration of CD3+ T cells in the neurohypophysis of mice that had been immunized with rabphilin-3A. Additionally, there was a linear association between the number of T cells specific for rabphilin-3A in PBMCs and the number of CD3+ T cells infiltrating the neurohypophysis. In conclusion, we suggest that rabphilin-3A is a pathogenic antigen, and that T cells specific for rabphilin-3A are involved in the pathogenesis of neurohypophysitis in mice. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Cullin-associated NEDD8-dissociated protein 1, a novel interactor of rabphilin-3A, deubiquitylates rabphilin-3A and regulates arginine vasopressin secretion in PC12 cells

The molecular mechanism involved in the exocytosis of arginine vasopressin (AVP) is not fully known. Rabphilin-3A has been suggested as a novel autoantigen in infundibulo-neurohypophysitis (LINH), which leads to central diabetes insipidus through insufficient secretion of AVP. However, the role of rabphilin-3A in the pathogenesis of LINH remains unclear. Thus, the aim of the present study was to identify proteins binding rabphilin-3A in the posterior pituitary. Using glutathione S-transferase (GST)-pulldown assays and proteomic analyses, cullin-associated NEDD8-dissociated protein 1 (CAND1) was identified as a rabphilin-3A-binding protein in the posterior pituitary. Co-immunoprecipitation assays indicated that CAND1 interacted endogenously with rabphilin-3A. In addition, immunohistochemistry experiments showed that CAND1 immunoreactivity was detected mainly in the posterior pituitary, intermediate lobe, and the supraoptic nucleus in the hypothalamus, and less in the anterior lobe, partially co-localizing with rabphilin-3A. Overexpression of CAND1 resulted in deubiquitylation of rabphilin-3A in PC12 cells. Moreover, overexpression of CAND1 in PC12 cells co-transfected with AVP enhanced both basal and KCl-stimulated AVP secretion. The findings indicate that CAND1 inhibits the ubiquitylation of rabphilin-3A and positively regulates AVP secretion. These data shed light on a novel potential mechanism involving rabphilin-3A in AVP secretion, and suggest a new role of CAND1 as a regulator of hormone or neurotransmitter secretion.

Evaluation and treatment of Langerhans cell histiocytosis patients with central nervous system abnormalities: Current views and new vistas

Central nervous system (CNS) involvement in Langerhans cell histiocytosis (LCH) can include mass lesions of the hypothalamic pituitary axis, choroid plexus, cerebrum, and cerebellum or magnetic resonance imaging (MRI) signal abnormalities of the cerebellum, pons, and basal ganglia. The term neurodegenerative (ND) CNS-LCH has been given to the MRI signal abnormalities and neurologic dysfunction, although initially patients may have no clinical symptoms. Standardized evaluations to better understand the natural history and response to therapy are needed. We propose guidelines for clinical, radiologic, and physiologic tests as a framework for developing the best methods of evaluation, which can then be tested in prospective treatment protocols.

Clinical presentation and outcome of children with central diabetes insipidus associated with a self-limited or transient pituitary stalk thickening, diagnosed as infundibuloneurohypophysitis

OBJECTIVE

Despite lymphocytic or autoimmune infundibuloneurohypophysitis (INH) is an increasingly recognized aetiology in children with central diabetes insipidus (CDI); clinical data on epidemiology (clinical evolution, predisposing factors, complications), diagnosis and management of this entity are limited and mostly based on published case reports. The aim of this study was to gain a broader insight in the natural history of this disease by analysing the clinical presentation, radiological pituitary stalk changes, associated autoimmunity and hormonal deficiencies in children with CDI and a self-limiting or transient stalk thickening (ST), diagnosed as autoimmune infundibuloneurohypophysitis, during the last 15 years in four Belgian university hospitals.

DESIGN AND PATIENTS

The medical files of nine CDI patients with a ST at initial presentation and no signs of Langerhans cell histiocytosis or germinoma at presentation and/or during follow-up of more than 1.5 years were reviewed.

RESULTS

Age at presentation ranged from 3 to 14 years. Two patients had a positive family history of autoimmunity. Three children presented with associated growth failure, two with nausea and one with long-standing headache. Median maximal diameter of the stalk was 4.6 mm (2.7-10 mm). Four patients had extra-pituitary brain anomalies, such as cysts. One patient had central hypothyroidism, and another had a partial growth hormone deficiency at diagnosis. Within a mean follow-up of 5.4 (1.5-15) years, stalk thickening remained unchanged in two patients, regressed in one and normalized in six children. CDI remained in all, while additional pituitary hormone deficiencies developed in only one patient.

CONCLUSIONS

In this series of children INH with CDI as initial presentation, CDI was permanent and infrequently associated with anterior pituitary hormone deficiencies, despite a frequent association with nonstalk cerebral lesions.

Usefulness of anti-rabphilin-3A antibodies for diagnosing central diabetes insipidus in the third trimester of pregnancy

We report a 27-year-old pregnant woman with polyuria, polydipsia and headache in the third trimester of pregnancy. Hypernatremia (153 mEq/L), high plasma osmolality (300 mOsm/kgH2O) and low urinary osmolality (92 mOsm/kgH2O) were observed at the admission to our hospital. Plasma arginine vasopressin (AVP) level was inappropriately low (2.2 pg/mL) compared to the high plasma osmolality. Plasma AVP responses to hypertonic-saline infusion were blunted, and her urine osmolality increased in response to desmopressin. The diagnosis of central diabetes insipidus was made from these results. Magnetic resonance imaging (MRI) of hypothalamic-pituitary region demonstrated a significant enlargement of the pituitary stalk, suggesting the presence of hypophysitis. In addition, serum anti-rabphilin-3A antibodies that have been recently reported as a biomarker of lymphocytic infundibulo-neurohypophysitis, were positive. Diabetes insipidus continued after delivery, suggesting that polyuria was not mainly due to excessive vasopressinase activity or reduced renal sensitivity to AVP by prostaglandin E2 that can cause temporal polyuria during pregnancy. We therefore clinically diagnosed central diabetes insipidus due to lymphocytic infundibulo-neurohypophysitis, without performing invasive transsphenoidal pituitary biopsy. This case suggested the usefulness of anti-rabphilin-3A antibodies for the etiological diagnosis of central diabetes insipidus during pregnancy.

Anti-pituitary antibodies against corticotrophs in IgG4-related hypophysitis

PURPOSE

IgG4-related disease is a systemic inflammatory disease characterized by infiltration of IgG4-positive plasma cells into multiple organs, including the pituitary gland. Autoimmunity is thought to be involved in the pathogenesis of IgG4-related disease. The diagnosis of IgG4-related hypophysitis (IgG4-RH) is difficult because its clinical features, such as pituitary swelling and hypopituitarism, are similar to those of other pituitary diseases, including lymphocytic hypophysitis and sellar/suprasellar tumors. The presence and significance of anti-pituitary antibodies (APA) in IgG4-RH is unclear.

METHODS

In this case-control study, we used single indirect immunofluorescence on human pituitary substrates to assess the prevalence of serum APA in 17 patients with IgG4-RH, 8 control patients with other pituitary diseases (lymphocytic infundibulo-neurohypophysitis, 3; craniopharyngioma, 2; germinoma, 3), and 9 healthy subjects. We further analyzed the endocrine cells targeted by the antibodies using double indirect immunofluorescence.

RESULTS

APA were found in 5 of 17 patients with IgG4-RH (29%), and in none of the pituitary controls or healthy subjects. The endocrine cells targeted by the antibodies in the 5 IgG4-RH cases were exclusively corticotrophs. Antibodies were of the IgG1 subclass, rather than IgG4, in all 5 cases, suggesting that IgG4 is not directly involved in the pathogenesis. Finally, antibodies recognized pro-opiomelanocortin in 2 of the cases.

CONCLUSIONS

Our study suggests that autoimmunity is involved in the pathogenesis of IgG4-RH and that corticotrophs are the main antigenic target, highlighting a possible new diagnostic marker for this condition.