Autoantibodies against pituitary proteins in patients with adrenocorticotropin-deficiency

Clinical Heterogeneity of Acquired Idiopathic Isolated Adrenocorticotropic Hormone Deficiency

OBJECTIVE

Heterogeneous clinical characteristics are observed in acquired isolated adrenocorticotropic hormone (ACTH) deficiency (IAD); however, its classification remains to be established because of its largely unknown pathophysiology. In IAD, anti-pituitary antibodies have been detected in some patients, although their significance remains unclear. Therefore, this study aimed to classify patients with IAD and to clarify the significance of anti-pituitary antibodies.

DESIGN AND METHODS

We analyzed 46 consecutive patients with IAD. Serum anti-pituitary antibodies were analyzed via immunofluorescence staining using a mouse pituitary tissue. Principal component and cluster analyses were performed to classify IAD patients based on clinical characteristics and autoantibodies.

RESULTS

Immunofluorescence analysis using the sera revealed that 58% of patients showed anti-corticotroph antibodies and 6% of patients showed anti-follicular stellate cell (FSC) antibodies. Principal component analysis demonstrated that three parameters could explain 70% of the patients. Hierarchical cluster analysis showed three clusters: Groups A and B comprised patients who were positive for anti-corticotroph antibodies, and plasma ACTH levels were extremely low. Groups A and B comprised middle-aged or elderly men and middle-aged women, respectively. Group C comprised patients who were positive for the anti-FSC antibody and elderly men; plasma ACTH levels were relatively high.

CONCLUSIONS

Patients with IAD were classified into three groups based on clinical characteristics and autoantibodies. The presence of anti-corticotroph antibody suggested severe injury to corticotrophs. This new classification clearly demonstrated the heterogeneity in the pathogenesis of IAD.

Incidence of pituitary autoantibodies in idiopathic diabetes insipidus

Diabetes insipidus is a disorder resulting from insufficient action of vasopressin (ADH) characterized by excretion of highly diluted urine in large amounts. Idiopathic diabetes insipidus is associated with the presence of both autoantibodies against ADH-secreting neurons and pituitary autoantibodies. The aim of the present study was to evaluate the occurrence of autoantibodies against the pituitary microsomal fraction. The study included 33 sera of diabetes insipidus patients and 10 control sera obtained from 10 healthy persons. In all patients the secretion of pituitary hormones and thyroid autoantibodies was assessed. Human pituitaries were obtained during autopsy and homogenized in 0.01 mol/l pH 7.4 phosphate buffer. In addition, for the autoantibody evaluation, the electrophoretic method of separation in polyacrylamide gel and western blot were employed. Among the 33 subjects, in 23 patients the presence of autoantibodies against the pituitary was shown. Sera of 15 patients reacted with the pituitary microsomal fraction protein of 55 kDa. In other cases, 10 sera reacted with the pituitary antigen of 67 kDa. In addition, 5 sera reacted with the 60 kDa antigen, 5 sera with 52 kDa protein, 3 sera with 105 kDa protein, 3 sera with the 97 kDa antigen and 2 sera with pituitary antigen of 92 kDa weight. In our study, based on the immunoblotting method, we observed that pituitary autoantibodies against 55, 60 and 67 kDa antigens occurred frequently.

Autoantibodies reactive to adrenocorticotropic hormone can alter cortisol secretion in both aggressive and nonaggressive humans

Violent aggression in humans may involve a modified response to stress, but the underlying mechanisms are not well understood. Here we show that naturally present autoantibodies reactive to adrenocorticotropic hormone (ACTH) exhibit distinct epitope-binding profiles to ACTH peptide in subjects with a history of violent aggression compared with controls. Namely, while nonaggressive male controls displayed a preferential IgG binding to the ACTH central part (amino acids 11-24), subjects who had committed violent acts of aggression had IgG with increased affinity to ACTH, preferentially binding to its N terminus (amino acids 1-13). Purified IgGs from approximately half of the examined sera were able to block ACTH-induced cortisol secretion of human adrenal cells in vitro, irrespective of the source of sample (from a control subject or a violent aggressor). Nevertheless, in the resident-intruder test in mice, i.p. injection of residents with ACTH and IgG from aggressive subjects, but not from control subjects, shortened latency for the first attack against intruders. Immunohistochemical screening of violent aggressors' sera on rat brain and pituitary sections did not show IgG binding to ACTH-producing cells, but 4 of 16 sera revealed selective binding to a nonidentified antigen in vasopressinergic neurons of the hypothalamic paraventricular and supraoptic nuclei. Thus, the data show that ACTH-reactive plasmatic IgGs exhibit differential epitope preference in control and violently aggressive subjects. These IgGs can modulate ACTH-induced cortisol secretion and, hence, are involved in the regulation of the stress response. However, the possible role of ACTH-reactive autoantibodies in aggressive behavior needs further investigation.

Anti-Ma-1 and Anti-Ma-2 Antibodies in Isolated Fatal Hypothalamitis

Lymphocytic hypothalamitis (LHT) is a rare disease characterized by pituitary dysfunction, autonomic instability, metabolic disturbances, and neuropsychiatric disorders. We report the case of a 30-year-old man found to have LHT that progressed despite treatment with methylprednisolone and intravenous immunoglobulin (IVIG). A literature review was conducted to identify prior studies pertaining to LHT. Our patient presented with several weeks of fatigue, cold intolerance, weight loss, confusion, and headache. Laboratory tests were consistent with panhypopituitarism. Brain magnetic resonance imaging revealed an infiltrative enhancing mass in the area of the hypothalamus, and stereotactic biopsy findings showed reactive inflammatory changes. A course of hormone replacement (levothyroxine), methylprednisolone, and IVIG was initiated. The patient’s course was complicated by a fatal tonsillar herniation. Autopsy revealed LHT. The diagnosis and management of autoimmune LHT are challenging. The entity should be considered in the setting of panhypopituitarism with a hypothalamic mass. Differentiating paraneoplastic and nonparaneoplastic hypothalamitis should be established for management and prognosis. Definitive treatment remains unclear; treatment with corticosteroids should be attempted, followed by consideration of other immunosuppressive agents, such as rituximab. If a paraneoplastic syndrome is suspected, management should also be directed toward the primary tumor.

Pituitary Microsomal Autoantibodies in Patients with Childhood-Onset Combined Pituitary Hormone Deficiency: an Antigen Identification Attempt

The role of autoimmunization in the pathogenesis of pituitary disorders is poorly understood. The presence of pituitary autoantibodies (APA) has been detected in various pituitary disorders. Their role, however, remains elusive. Childhood-onset combined pituitary hormone deficiency (CPHD) may be caused by environmental or genetic factors. In some of patients, causes of the disease remain unclear and contributions of autoimmune processes have been postulated. The aim of this study was to identify the microsomes-derived pituitary antigens (MPA) as potential immunogenic autoantigens in patients with hypopituitarism, therefore 62 CPHD patients, 100 healthy controls and five autoimmune polyglandular syndrome type II (APS II) patients were included in the study. The clinical evaluation included hormonal tests and magnetic resonance imaging of the pituitary. The sources of MPA were pituitary glands taken from autopsies. Isolated MPA were then separated on SDS-PAGE gel and incubated with sera obtained from patients and controls. Microsomal APA were detected using Western blot and radioimmunological method. In all CPHD and APS II patients and in 9 % individuals from control group marked immunoreactivity was detected against MPA. Antibodies showed high affinity to 67, 60, 50 and 36 kDa MPAs. Since the identified autoantigens were of unknown nature, an in silico exploration of UniProt database was applied and indicated their possible relationship with chaperones, golgins and already known autoantigens like GAD67. Reactivity against MPA indicates that these proteins certainly play a role in the processes undergoing within pituitary of CPHD patients. The identification and further detailed studies on their role in the pathogenesis of CPHD should be continued.

Longitudinal behavior of autoimmune GH deficiency: from childhood to transition age

BACKGROUND

Some cases of apparently idiopathic GH deficiency (GHD) may be caused by pituitary autoimmunity.

OBJECTIVE

To study the variations in pituitary function and antipituitary antibodies (APA) from childhood to transition age in patients with apparently idiopathic GHD.

DESIGN

We conducted a longitudinal study.

PATIENTS AND METHODS

Pituitary function and APA detection by immunofluorescence were investigated in 24 childhood patients with isolated GHD before starting recombinant GH therapy and after the stopping of this therapy in transition age. Sera of patients positive for APA were processed by double immunofluorescence to identify their pituitary target.

RESULTS

At diagnosis, 16 out of 24 patients were APA positive targeting only somatotrophs (group 1), while the remaining eight were APA negative (group 2). When retested off therapy, 12 out of 16 patients in group 1 persisted being APA positive, while the remaining four became negative with recovery of pituitary function. All patients in group 2 persisted being APA negative but still showing GHD. Of the 12 patients persistently APA positive, eight with confirmed GHD showed APA still targeting somatotrophs, whereas four showed APA targeting only gonadotrophs associated with isolated hypogonadotropic hypogonadism (HH).

CONCLUSION

Patients with APA at middle but not at high titer in childhood may show a remission of autoimmune GHD in childhood after GH replacement therapy. As APA may shift their target in transition period, an early characterization of APA by double immunofluorescence is advisable in APA positive GHD patients showing delayed puberty, to allow an early diagnosis and an appropriate therapy, thus preventing the progression toward HH.

Identification of the novel autoantigen candidate Rab GDP dissociation inhibitor alpha in isolated adrenocorticotropin deficiency

Isolated adrenocorticotropin deficiency (IAD) is characterized by low or absent adrenocorticotropic hormone (ACTH) production. IAD is presumed to be caused in part by an autoimmune mechanism, and several lines of evidence have suggested the presence of anti-pituitary antibodies in IAD. However, the exact autoantigens remain unknown. The present study was designed to identify the autoantigen(s) in IAD using chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Rat anterior pituitary lysate was subjected to SDS-PAGE, and immunoblotting was performed using the sera from two patients with IAD and from a healthy subject. The bands detected by the patient serum samples, but not by the healthy subject sample, were excised, in-gel digested using trypsin, and subjected to LC-MS/MS analysis. On immunoblots, a 51-kDa band in the insoluble pellet was detected by the sera from the IAD patients but not from the healthy subject. Mass spectrometric analysis revealed the 51-kDa band contained Rab guanine nucleotide dissociation inhibitor (GDI) alpha. Consistent with the mass spectrometric analysis, a recombinant full-length human Rab GDI alpha was recognized by the two IAD patient samples but not by the healthy subject sample using immunoblotting. In total, anti-Rab GDI alpha antibodies were detected in serum samples from three of five patients with IAD (60%) but were absent in 5 healthy subjects. In addition, Rab GDI alpha was expressed in the anterior pituitary. In conclusion, it appears that Rab GDI alpha is a candidate autoantigen involved in IAD, and that anti-Rab GDI alpha antibodies are present predominantly in patients with IAD.

Pituitary gonadotropins and autoimmunity

Autoimmune disease occurs when the body produces an inappropriate immune response against its own tissues producing antibodies, called autoantibodies, reacting to specific antigens. Studies regarding the presence of an autoimmune process specifically involving gonadotropins date from over than 20 years ago, when antibodies to gonadotropic-secreting cells were found by immunofluorescence in sera from a group of patients affected by cryptorchidism. Later on, antibodies detected by the same technique, and directed to the same cells were also found at high titer in sera from patients affected by hypogonadotropic hypogonadism, Kallmann's syndrome, lymphocytic hypophysitis with isolated gonadotropin deficiency, as well as autoimmune polyendocrine syndrome. Concerning the autoimmune target/s within the gonadotropic cells, rarely autoantibodies were found labeling gonadotropins while in a large number of cases, auto-antigens remained to be identified. Since pituitary gonadotropins are fundamental for the sexual maturity and reproductive mechanisms, patients with infertility were largely investigated by enzyme-linked immunosorbent assay for the presence of circulating antibodies likely interfering with gonadotropin activity. In infertile women, autoantibodies to gonadotropins were found related to ovarian autoimmunity, ovarian disorders that cause infertility and also associated with in vitro fertilization treatments. In infertile men, autoantibodies to gonadotropins may alter the testicular spermatogenesis and cause apoptosis of the spermatogenic cells. In conclusion, circulating antibodies were found labeling gonadotropic cells and/or gonadotropins, and in both cases they could create dysfunctions in gonadotropin related mechanism. The intriguing question of what can cause the production of such autoantibodies is not clear yet.

Intermediate lobe immunoreactivity in a patient with suspected lymphocytic hypophysitis

Lymphocytic hypophysitis is an organ-specific autoimmune disease characterised by destruction of pituitary hormone-secreting cells due to attack by self-reactive T lymphocytes. The spectrum of pituitary autoantibodies characterised by indirect immunofluorescence (IF) in these patients has not been substantially defined. The purpose of this study was to determine the spectrum of pituitary autoantibodies in 16 lymphocytic hypophysitis patients. Pituitary sections were prepared from guinea pigs and sera from 16 lymphocytic hypophysitis patients (13 biopsy proven and 3 suspected cases) and 13 healthy controls were evaluated for immunoreactivity to the pituitary tissue by immunofluorescence. A single patient was found to have high titre pituitary autoantibodies against guinea pig pituitary tissue. Immunoreactivity was directed against cells of the intermediate lobe. We present the case report of the patient who is a 24 year old woman that presented with headaches, polyuria and polydipsia. A uniformly enlarged pituitary mass was visible on MRI and a diagnosis of suspected lymphocytic hypophysitis was made. Based on our IF study, we postulate this patient has an autoimmune process directed towards the major cell type in the intermediate lobe, the melanotroph. Pre-adsorption with peptides representing adrenocorticotropic hormone, α-melanocyte stimulating hormone or β-endorphin did not affect the IF signal suggesting our patient's pituitary autoantibodies may target some other product of Proopiomelanocortin (POMC) processing, such as corticotrophin-like intermediate peptide or γ-lipoprotein. Alternatively, the autoantibodies may target a peptide completely unrelated to POMC processing.

Diagnosis and classification of autoimmune hypophysitis

Autoimmmune hypophysitis (AH) is the consequence of an immune-mediated inflammation of the pituitary gland. The initial pituitary enlargement, secondary to infiltration and oedema, can evolve to remission, for spontaneous or pharmacological resolution of the inflammation, or evolve to progressive diffuse destruction with gland atrophy for fibrotic replacement, thus leading to various degrees of pituitary dysfunction. The autoimmune process against the pituitary gland is made evident by the appearance of circulating autoantibodies (APA), mainly detected by indirect immunofluorescence on cryostatic sections of human or primate pituitary. Among the target autoantigens recognized by APA are alpha-enolase, gamma-enolase, the pituitary gland specific factors (PGSF) 1 and 2 and corticotroph-specific transcription factor (TPIT). However, the low diagnostic sensitivity and specificity of APA for AH strongly limit the clinical use of this marker. AH should be considered in the differential diagnosis of non-secreting space-occupying lesions of sella turcica, to avoid misdiagnosis that may lead to an aggressive surgery approach, since endocrine dysfunction and the compressive effect may be transient.

Bartter syndrome type 3 in an elderly complicated with adrenocorticotropin-deficiency

Bartter syndrome (BS) is a disorder with normotensive hypokalemic alkalosis and hyperreninemic hyperaldosteronemia. BS affects infants or early childhood. Patients with BS type 3 harbor mutation in CLCNKB, Cl channel Kb. Gitelman syndrome (GS) is a disorder in childhood, with mutation in SLC12A3. Isolated adrenocorticotropin deficiency (IAD) causes secondary adrenal insufficiency. Neither elderly cases, nor cases with IAD were previously reported in BS. A 72-year-old man was admitted with acute adrenal crisis. He had been treated for IAD for 19 years. He had no trouble during perinatal period, delivery, and growth. After the recovery from adrenal crisis, laboratory tests revealed hypokalemia; 3.0 mEq/L (normal: 3.5-4.5), impaired renal function: eGFR; 37.6 mL/min/1.73 m2, normomagnesemia; 2.1 mg/dL (1.7-2.3), hyperreninemia; 59.4 ng/mL/h (0.2-2.7), hyperaldosteronemia; 23.5 ng/dL (3.0-15.9), and normal urinary ratio of calcium/creatinine. In diuretic tests, he showed a fine response to furosemide, and a mild response to thiazide. In genetic tests, no mutation of SLC12A3 was found and homozygous mutation: c.1830 G > A in CLCNKB was shown. Thus he was diagnosed as BS type 3. Current case presented with unusual features as BS type 3, 1) his late and mild clinical manifestation suggested GS rather than BS, 2) laboratory data and diuretics tests did not show typical features as BS, and 3) IAD and chronic renal failure altered electrolyte metabolism. In conclusion, current case implies that BS type 3 should be considered even in elderly cases with normotensive hypokalemia, and highlights importance of endocrinological and genetic examinations.

Purification of pituitary autoantigen by column liquid chromatography and chromatofocusing

Introduction

Pituitary autoantibodies can be determined both in patients with pituitary disease as well as patients with autoimmune endocrine diseases. The purpose of the study was to isolate and purify pituitary autoantigen using sera of patients and the microsomal fraction of the pituitary.

Material and methods

To isolate a pituitary autoantigen, patient sera were used, which showed a strong immune response to pituitary antigens. Pituitary microsomal fractions were prepared from pituitary tissue homogenates. In the study, sera of patients with pituitary disease, Addison and Graves’ disease were used. The initial stages were carried out by affinity chromatography on CN -Br sepharose column whereas purification was continued by column liquid chromatography on AcA54 Ultrogel. Chromatofocusing was performed by Polybuffer exchanger PBE 94.

Results

¹²⁵I-labeled pituitary antigens after isolation appeared in column chromatography in three peaks. The first peak contained 50-70 kDa proteins, the second peak – 17 to 22 kDa proteins and the third peak contains ¹²⁵-iodides. Three fractions obtained from filtration on Ultrogel were separated in a polyacrylamide gel. In the first peak two bands 67 and 55 kDa appeared. The second peak contained low molecular weight substances, and the third peak contained ¹²⁵I. The first peak from Ultrogel was isolated by chromatofocusing – the first peak with pH 5.9 and the second one with pH 4.9.

Conclusions

Isolation and purification of pituitary autoantigen with the use of column liquid chromatography and chromatofocusing resulted in obtainment of two antigenic proteins of specific gravity of 67 and 55 kDa.

Growth hormone and proopiomelanocortin are targeted by autoantibodies in a patient with biopsy-proven IgG4-related hypophysitis

Hypophysitis is a chronic inflammation of the pituitary gland often caused by autoimmunity. Among the autoimmune diseases it is one of the few where the autoantigens remain to be identified. The goal of the paper was to characterize the antigenic profile in a previously reported patient with IgG4-related hypophysitis. Immunofluorescence and immunoblotting were performed to detect antibodies to human pituitary proteins. The proteins recognized by western blotting were then submitted to mass spectrometry for sequencing. The patient's autoantibodies recognized two unique bands around 40 and 30 kDa on immunoblotting. Sequencing revealed one peptide from proopiomelanocortin in the 40 kDa band and four peptides from growth hormone in the 30 kDa band. This work represents the first antigenic profile in IgG4-related hypophysitis, and the first recognition of proopiomelanocortin as a possible pituitary autoantigen. In addition, the work supports previous suggestions of growth hormone as a pituitary autoantigen. Further studies are needed to prove the pathogenicity and diagnostic utility of these two pituitary proteins.

Identification of TPIT and other novel autoantigens in lymphocytic hypophysitis: immunoscreening of a pituitary cDNA library and development of immunoprecipitation assays

BACKGROUND

Lymphocytic hypophysitis is an organ-specific autoimmune disease of the pituitary gland. A specific and sensitive serological test currently does not exist to aid in the diagnosis.

OBJECTIVE

To identify target autoantigens in lymphocytic hypophysitis and develop a diagnostic assay for these proteins.

DESIGN/METHODS

A pituitary cDNA expression library was immunoscreened using sera from four patients with lymphocytic hypophysitis. Relevant cDNA clones from screening, along with previously identified autoantigens pituitary gland-specific factor 1a and 2 (PGSF1a and PGSF2) and neuron-specific enolase (NSE) were tested in an in vitro transcription and translation immunoprecipitation assay. The corticotroph-specific transcription factor, TPIT, was investigated separately as a candidate autoantigen.

RESULTS

Significantly positive autoantibody reactivity against TPIT was found in 9/86 hypophysitis patients vs 1/90 controls (P = 0.018). The reactivity against TPIT was not specific for lymphocytic hypophysitis with autoantibodies detectable in the sera from patients with other autoimmune endocrine diseases. Autoantibodies were also detected against chromodomain-helicase-DNA binding protein 8, presynaptic cytomatrix protein (piccolo), Ca(2+)-dependent secretion activator, PGSF2 and NSE in serum samples from patients with lymphocytic hypophysitis, but at a frequency that did not differ from healthy controls. Importantly, 8/86 patients with lymphocytic hypophysitis had autoantibodies against any two autoantigens in comparison with 0/90 controls (P = 0.0093).

CONCLUSIONS

TPIT, a corticotroph-specific transcription factor, was identified as a target autoantigen in 10.5% of patients with lymphocytic hypophysitis. Further autoantigens related to vesicle processing were also identified as potential autoantigens with different immunoreactivity patterns in patients and controls.

Detection of antipituitary and antihypothalamus antibodies to investigate the role of pituitary or hypothalamic autoimmunity in patients with selective idiopathic hypopituitarism

OBJECTIVE

Antipituitary (APA) but not antihypothalamus antibodies (AHA) have been investigated in patients with idiopathic hypopituitarism. This study searched for APA and AHA in some of these patients to investigate whether pituitary or hypothalamic autoimmunity could play a role in their pituitary dysfunction.

DESIGN

Sixty-six patients with selective idiopathic hypopituitarism were studied: 27 with ACTH deficiency, 20 with GH deficiency and 19 with hypogonadotropic hypogonadism. Twenty patients with hypopituitarism secondary to hypophysectomy and 50 healthy subjects were enrolled as controls.

MEASUREMENTS

Antipituitary and AHA were evaluated by indirect immunofluorescence in sera of patients and controls. Positive sera were retested by a four-layer double immunofluorescence to identify the cells targeted by these antibodies.

RESULTS

Antipituitary were present at high titre in 4 of 27 patients with ACTH deficiency (14·8%), 4 of 20 with GH deficiency (26%) and 5 of 19 with hypogonadotropic hypogonadism (21%) and targeted, respectively, corticotrophs, somatotrophs and gonadotrophs. AHA were found at high titre only in 5 patients with ACTH deficiency (18·5%), mostly targeting corticotrophin-releasing hormone-secreting cells; none of these 5 patients resulted positive for antipituitary antibodies. Among the controls, only 1 hypophysectomized patient resulted APA positive at low titre.

CONCLUSIONS

Our results suggest that in patients with selective idiopathic hypopituitarism, detection of APA or AHA could better characterize an autoimmune process involving the pituitary or hypothalamus, respectively. In particular, detection of antibodies targeting selectively ACTH-secreting or corticotrophin-releasing hormone-secreting cells may differentiate, respectively secondary from tertiary variants of autoimmune hypoadrenalism.

Adenohypophysitis in rat pituitary allografts

The histological, immunohistochemical and ultrastructural alterations in 81 pituitary allografts from Lewis rats transplanted beneath the renal capsule of Wistar rats were investigated. Intrasellar pituitaries of rats bearing allografts were also examined. Recipient rats were sacrificed at various time points after transplantation. Two days after transplantation, the central portion of the allografts demonstrated ischaemic necrosis. A week later, massive mononuclear cell infiltrates consisting primarily of lymphocytes and to a lesser extent, macrophages, plasma cells and granulocytes became prominent. At about three to four weeks after transplantation, the mononuclear cell infiltrate diminished; the surviving adenohypophysial cells, mainly prolactin (PRL) cells, increased in number and necrosis was replaced by connective tissue. No histological changes were noted in the intrasellar pituitaries of rats bearing allografts. Immunohistochemistry demonstrated that the surviving adenohypophysial cells were mainly PRL-producing cells. Electron microscopy revealed adenohypophysial cell destruction, a spectrum of inflammatory cells and, in late phase, accumulation of fibroblasts and collagen fibres. PRL cells were the prominent cell types; they increased in number. It appears that pituitary allografts are 'foreign' and evoke an immune response, suggesting that they may be used as an experimental animal model for morphological investigation of the development and progression of adenohypophysitis, a rare disease occurring mainly in young women often associated with pregnancy.

[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.

Autoimmunity as a possible cause of growth hormone deficiency

A possible autoimmune aggression to pituitary somatotrophs has been suggested by the occurrence of antipituitary antibodies (APA) directed against GH-secreting cells in some cases of GH deficiency (GHD) both in adults and in children and in some patients with autoimmune poliendocrine syndrome. We also detected APA in some patients with idiopathic short stature (ISS) and suggested that the presence of these antibodies could identify those of them prone to develop GHD. In fact, patients with ISS, resulted positive for APA at the first observation, during a longitudinal follow-up showed an impaired GH response to the stimuli in subsequent years suggestive of acquired GHD. Also in such patients we demonstrated that the target of APA were the somatotrophs and that an autoimmune attack to these cells may be the underlying cause of hormonal impairment in several children with GHD positive for APA. In this connection we suggested that in these patients an early iso-hormonal therapy with recombinant GH may be useful to interrupt or delay the progression towards a clinical GHD.

Pituitary autoimmunity: 30 years later

Pituitary autoimmunity encompasses a spectrum of conditions ranging from histologically proven forms of lymphocytic hypophysitis to the presence of pituitary antibodies in apparently healthy subjects. Hypophysitis is a rare but increasingly recognized disorder that typically presents as a mass in the sella turcica. It mimics clinically and radiologically other non-functioning sellar masses, such as the more common pituitary adenoma. Hypophysitis shows a striking temporal association with pregnancy, and it has been recently described during immunotherapies that block CTLA-4. Several candidate pituitary autoantigens have been described in the last decade, although none has proven useful as a diagnostic tool. This review summarizes the advances made in the field since the publication of the first review on pituitary autoimmunity, and the challenges that await clarification.

Immunological and clinical aspects of lymphocytic hypophysitis

LYH (lymphocytic hypophysitis) is an autoimmune disease of the pituitary gland which can present with varying degrees of pituitary hormonal impairment and/or with symptoms related to pituitary enlargement. In this review, we provide an overview of the epidemiology, diagnosis, pathogenesis, treatment, and the role of organ-specific and antipituitary antibodies as potential markers of LYH. In addition, although the mechanisms underlying LYH are not completely understood, the role of prolactin, which plays an important part in maintaining immune system homoeostasis and is increased in the disease, is considered.

Prevalence and functional significance of antipituitary antibodies in patients with autoimmune and non-autoimmune thyroid diseases

BACKGROUND

Circulating antipituitary antibodies (APA) are markers of autoimmune hypophysitis, which may cause deficient pituitary function. The prevalence of APA in autoimmune thyroid disorders (AITD) is uncertain.

OBJECTIVES

The aims of this study were 1) to evaluate APA prevalence in a large series of patients with AITD and non-AITD and 2) to investigate the functional significance of APA by assessing pituitary function in APA-positive patients.

DESIGN AND SETTING

We conducted a health survey on consecutive AITD and non-AITD patients at a tertiary referral center (Department of Endocrinology, Pisa).

PATIENTS

Subjects, including 1290 consecutive patients with thyroid disorders (961 AITD and 329 non-AITD) and 135 controls, were enrolled in the study.

METHODS

APA (indirect immunofluorescence), free T(4), free T(3), TSH, and organ-specific autoantibodies were assayed in all patients. Functional pituitary evaluation was performed in most APA-positive patients.

RESULTS

APA frequency was higher in AITD (11.4%) than in non-AITD (0.9%; P < 0.0001) patients; all control subjects had negative APA tests. APA were more frequently found in Hashimoto's thyroiditis (13%) than in Graves' disease (7.1%; P = 0.05). Of 110 APA-positive AITD patients, 20 (18.2%) had autoimmune polyglandular syndrome, whereas 90 (81.8%) had apparently isolated AITD. APA positivity increased percentage of autoimmune polyglandular syndrome in our series from 10.4 to 13.5%. Of 110 APA-positive patients, 102 were submitted to dynamic testing for functional pituitary assessment; 36 patients (35.2%) had mild or severe GH deficiency (GHD). No additional anterior pituitary hormone deficiencies were found; one patient had central diabetes insipidus. Pituitary abnormalities at magnetic resonance imaging were found in most APA-positive GHD patients.

CONCLUSIONS

APA are frequently present in patients with AITD. Patients should be tested for APA because positive tests are associated with GHD.

Lymphocytic hypophysitis: report of two biopsy-proven cases and one suspected case with pituitary autoantibodies

Lymphocytic hypophysitis (LyH) is a rare inflammatory disease, considered to be autoimmune. LyH has mainly been reported in females and in relation to pregnancy or the post-partum period. We describe a 73-yr-old woman and a 63-yr-old male who were evaluated at our clinic because of pituitary hormone deficits. Both patients had pituitary masses suggestive of a pituitary adenoma on magnetic resonance imaging (MRI). Transsphenoidal pituitary surgery was performed and histopathological examinations revealed LyH in both cases. Clinical, laboratory, radiological and the histopathological findings in these two patients are discussed in detail. In addition, we report on a 79-yr-old man with partial hypopituitarism and empty sella. Screening of a human pituitary cDNA library with his serum revealed autoantibodies against secretogranin II. This is a protein commonly present in human gonadotrophs, thyreotrophs and corticotrophs. Since the patient selectively showed the corresponding pituitary insufficiencies, we speculate on an autoimmune background. Further studies may ascertain the importance of secretogranin II autoantibodies as markers for LyH.

Antipituitary antibodies recognizing growth hormone (GH)-producing cells in children with idiopathic GH deficiency and in children with idiopathic short stature

CONTEXT

Antipituitary antibodies (APA) recognizing GH-secreting cells may indicate an autoimmune pituitary involvement in adults with idiopathic GH deficiency (IGHD).

OBJECTIVE

We aimed 1) to investigate the presence of APA in prepubertal children with IGHD or idiopathic short stature (ISS), identifying the pituitary hormone-producing cells targeted by APA; and 2) to verify whether in patients with ISS the presence of APA could predict the development of GHD.

DESIGN

We performed a cross-sectional and partially longitudinal cohort study.

SETTING

The study was performed at the Endocrinology Unit and Pediatric Unit of the Second University and University Federico II of Naples, respectively.

PATIENTS

Twenty-six children with IGHD (group 1), 60 children with ISS (group 2), 33 children with GHD caused by lesions/abnormalities of the hypothalamus or pituitary (group 3), and 40 controls participated in the study. Nineteen children of group 2 were reevaluated after 2 yr.

MAIN OUTCOME MEASURES

IGF-I levels, GH secretion, and APA (by indirect immunofluorescence) were evaluated in all participants.

RESULTS

At study entry, APA recognizing GH-producing cells were detected in seven of 26 children in group 1 and in 14 of 60 in group 2. Two years later, all eight initially APA-positive and all 11 APA-negative of the 19 reevaluated patients persisted positive and negative, respectively. The reevaluation of GH secretion in these patients revealed the development of GHD in all but one of the APA-positive children but in none of the APA-negative ones.

CONCLUSIONS

IGHD in children can be frequently associated with APA targeting GH-secreting cells; thus, the detection of APA in children with ISS could identify those prone to develop GHD.