Western blot analysis of rat pituitary antigens recognized by human antipituitary antibodies

Clinical Characteristics of Primary Hypophysitis - A Single-Centre Series of 60 Cases

OBJECTIVE

Clinical data on primary hypophysitis are still scarce. Especially non-surgical cases are underreported. We sought to analyse clinical characteristics of primary hypophysitis, particularly in clinically diagnosed patients.

DESIGN

Retrospective single centre study in 60 patients with primary hypophysitis.

METHODS

Symptoms, MRI, histopathological findings, treatment and outcomes were analysed in 12 histopathologically and 48 clinically diagnosed patients. Diagnostic criteria for clinical diagnosis were: a) MRI findings compatible with primary hypophysitis; b) course of disease excluding other differential diagnoses. Mean duration of follow-up was 69 months.

RESULTS

Female sex was predominant (73%). Fatigue (52%), headache (38%) and diabetes insipidus (38%) were the most frequent symptoms. 42% had a concomitant autoimmune disease. The corticotropic, thyrotropic, gonadotropic, somatotropic axis was impaired in 67%, 57%, 52%, 20%, respectively. Men had a higher number of impaired hormone axes (p=0.022) with the gonadotropic axis being affected more frequently in men (p=0.001). Infundibular thickening (56%) and space occupying lesions (46%) were typical MRI findings. Pituitary size was frequently enlarged at presentation (37%) but diminished during observation (p=0.029). Histopathologically and clinically diagnosed cases did not differ.

CONCLUSIONS

The cohort of clinically diagnosed patients did not differ from our histopathologically diagnosed patients or from published cohorts with predominantly surgical patients. Thus, diagnosis of primary hypophysitis using clinical criteria seems feasible.

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.

Lymphocytic infundibulo-neurohypophysitis: a clinical overview

Lymphocytic infundibulo-neurohypophysitis is an uncommon inflammatory disorder postulated to be autoimmune in origin. Because of the location of inflammation, it selectively affects the posterior lobe of the pituitary (neurohypophysis) and pituitary stalk (infundibulum). The most common presentation is central diabetes insipidus. Although the definitive diagnosis is established histologically by a pituitary biopsy, radiological imaging can be valuable in diagnosing this condition. In this paper, we provide an overview of the pathophysiology, investigations, management, and outcomes of lymphocytic infundibulo-neurohypophysitis.

Coherent somatic mutation in autoimmune disease

BACKGROUND

Many aspects of autoimmune disease are not well understood, including the specificities of autoimmune targets, and patterns of co-morbidity and cross-heritability across diseases. Prior work has provided evidence that somatic mutation caused by gene conversion and deletion at segmentally duplicated loci is relevant to several diseases. Simple tandem repeat (STR) sequence is highly mutable, both somatically and in the germ-line, and somatic STR mutations are observed under inflammation.

RESULTS

Protein-coding genes spanning STRs having markers of mutability, including germ-line variability, high total length, repeat count and/or repeat similarity, are evaluated in the context of autoimmunity. For the initiation of autoimmune disease, antigens whose autoantibodies are the first observed in a disease, termed primary autoantigens, are informative. Three primary autoantigens, thyroid peroxidase (TPO), phogrin (PTPRN2) and filaggrin (FLG), include STRs that are among the eleven longest STRs spanned by protein-coding genes. This association of primary autoantigens with long STR sequence is highly significant (p<3.0x10(-7)). Long STRs occur within twenty genes that are associated with sixteen common autoimmune diseases and atherosclerosis. The repeat within the TTC34 gene is an outlier in terms of length and a link with systemic lupus erythematosus is proposed.

CONCLUSIONS

The results support the hypothesis that many autoimmune diseases are triggered by immune responses to proteins whose DNA sequence mutates somatically in a coherent, consistent fashion. Other autoimmune diseases may be caused by coherent somatic mutations in immune cells. The coherent somatic mutation hypothesis has the potential to be a comprehensive explanation for the initiation of many autoimmune diseases.

Pituitary autoimmunity in patients with diabetes mellitus and other endocrine disorders

OBJECTIVE

Pituitary autoimmunity is often found in association with other endocrine autoimmune or non-autoimmune diseases. Aim of the study was to assess the prevalence of serum pituitary antibodies (PitAb) in patients with Type 1 diabetes mellitus (T1DM) or Type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

In this casecontrol study 111 patients with T1DM, 110 patients with T2DM, and 214 healthy controls were enrolled in a tertiary referral center. Pituitary, thyroperoxidase, thyroglobulin, 21-hydroxylase, and parietal cell antibodies were assessed in all cases. Endocrine function was further assessed by basal hormone measurement and by dynamic tests, as well as a pituitary magnetic resonance imaging (MRI) was performed in those patients found positive for PitAb.

RESULTS

PitAb prevalence was higher in T1DM (4 out of 111, 3.6%) than in T2DM (0 out of 110, p=0.045) and in healthy subjects (1 out of 214, 0.5% p=0.029). Prevalence of other autoimmune diseases was significantly higher in patients with T1DM (45 out of 111, 40.5%) when compared with patients with T2DM (18 out of 110 T2DM, 16.3%, p<0.001). Patients with T1DM and PitAb positivity were found with a pituitary lesion at MRI in 2 cases and pituitary dysfunction in one case.

CONCLUSIONS

A significant association between pituitary autoimmunity and T1DM was found, in particular in subjects with one or more other endocrine autoimmune diseases.

Lymphocytic hypophysitis: disease spectrum and approach to diagnosis and therapy

Lymphocytic hypophysitis (LYH) is a neuroendocrine disorder characterized by autoimmune inflammation of the pituitary gland with various degrees of pituitary dysfunction. The histopathology consists of an initial monoclonal lymphocytic infiltrate, which can heal with minimal sequela or progress to fibrosis and result in permanent hypopituitarism. Coexistence of other autoimmune conditions is reported in 25-50% of cases and pituitary autoantibodies have been detected in up to 70% of biopsy-proven cases. The clinical presentation varies depending on the pituitary segment that is more severely affected. In lymphocytic adenohypophysitis (LAH) an early destruction of the ACTH-producing cells is characteristic. Other anterior pituitary hormones can also be affected but posterior pituitary involvement is absent or minimum. Lymphocytic Infundibuloneurohypophysitis (LINH) typically presents as acute onset diabetes insipidus (DI) with intracranial mass-effect symptoms. A combination of extensive anterior pituitary involvement and DI characterizes lymphocytic Infudibulopanhypophysitis (LIPH). The diagnosis can be challenging in many cases, because distinction from pituitary adenomas and other sellar masses is not obvious. Significant efforts have been made to identify specific serum markers, but it would seem unlikely that this approach will ever have the specificity to replace histopathological examination of a surgical specimen. Diagnostic criteria have been proposed to help in the decision-making process and to avoid, whenever possible, unnecessary invasive procedures. The therapeutic approach is controversial and, although transsphenoidal surgery is often performed, a conservative medical management is justified in many cases, given the self-limited nature of the inflammatory process. This paper reviews the etiology, epidemiology, clinical and radiological findings, diagnosis and management of LYH.

Association of antipituitary antibody and type 2 iodothyronine deiodinase antibody in patients with autoimmune thyroid disease

Antipituitary antibody (APA) has been reported to be detected in patients with autoimmune thyroid disease. Type 2 iodothyronine deiodinase (D2) is expressed in both pituitary gland and thyroid gland. We studied the association of APA and D2 peptide antibody in patients with autoimmune thyroid disease. Rat pituitary gland homogenate and D2 peptide were used as antigens in the present study. APA and D2 peptide antibodies were measured by enzyme-linked immunosorbent assay (ELISA) in sera obtained from 42 patients with Hashimoto's disease, 26 patients with Graves' disease and 70 healthy control subjects. Moreover, D2 activity precipitation assay was performed in some patients with Hashimoto's disease. APA and D2 peptide antibody were elevated in patients with Hashimoto's disease and patients with Graves' disease, compared with control subjects. APA was positive in 32.4% (22/68), D2 peptide antibody was positive in 26.5% (18/68) of patients with autoimmune thyroid disease. APA was positive in 31.0% (13/42) of patients with Hashimoto's disease and 34.6% (9/26) of patients with Graves' disease. D2 peptide antibody was positive in 26.2% (11/42) of patients with Hashimoto's disease and 26.9% (7/26) of patients with Graves' disease. D2 peptide antibody was correlated with APA in patients with autoimmune thyroid disease. Moreover, precipitation of D2 activity was increased in some patients with Hashimoto's disease including a patient who also had idiopathic diabetes insipidus, and was correlated with D2 peptide antibody. These results suggest that D2 antibody may be associated with APA in patients with autoimmune thyroid disease.

Autoimmune hypophysitis

Autoimmune (lymphocytic) hypophysitis is a rare disease that should be considered in the differential diagnosis of any nonsecreting pituitary mass, especially when occurring during pregnancy or postpartum. We have analyzed 370 articles published from January 1962 to October 2004 and identified a total of 379 patients with primary lymphocytic hypophysitis. The present review synthesizes the clinical and research data reported in this body of scientific literature.

Detection of point mutation for human growth hormone in patients with anti-pituitary antibody positive type 1 diabetes mellitus

We investigated genetic mutations in the coding region of the human growth hormone (hGH) gene in anti-pituitary antibody (APA)-positive patients with type 1 diabetes mellitus (n = 6) or autoimmune thyroid diseases (n = 10) and in APA-negative, healthy controls (n = 10). A point mutation in the hGH gene was discovered in two patients with type 1 diabetes mellitus. No mutations were found in the hGH gene in control subjects, patients with autoimmune thyroid diseases (Hashimoto's thyroiditits, Graves' disease) or in the remaining four patients with type 1 diabetes mellitus. The mutation was located in the coding region for the second amino acid in the N-terminal region of hGH. This point mutation was identified in codon 2 in exon 2 of the hGH gene. We successfully developed an allele-specific amplification method for detecting this mutation using the polymerase chain reaction.

Anti-pituitary antibody-induced multiple endocrine disorders in mice

Circulating anti-pituitary antibodies (APAs) have been detected in patients with autoimmune diseases, although the role of autoantibodies in the pathogenesis of autoimmune diseases is still unclear. With the aim of elucidating the autoimmune mechanisms involved in patients with multiple endocrine disorders, we evaluated the pathological changes in the pituitary gland, thyroid, pancreas and adrenal gland of mice, both wild-type and using a murine model of autoimmune thyroid disease [MRL-lpr/lpr] that had been immunized with murine, rat, porcine or human pituitary glands. In four of seven mice, a 22 kD band corresponding to APA was detected by Western blotting in the serum from mice that had been immunized with human pituitary tissues but not in the serum from mice immunized with rat or pig tissue. Inflammatory changes were detected in all groups of mice, occurring in the hypophysis, pancreas and adrenal glands but not in the thyroid. In conclusion, APA-induced autoimmune endocrine disorders are likely to be important for studying the mechanisms involved in autoimmune syndromes.

Determination of antipituitary antibody in patients with endocrine disorders by enzyme-linked immunosorbent assay and Western blot analysis

The identification of pituitary antigens recognized by human antipituitary antibodies (APAs) is important in evaluating the pathophysiology of multiendocrine disorders linked to autoimmune factors. However, there is no convenient method for the quantitative analysis of circulating APAs. This study reports the development of an enzyme-linked immunosorbent assay (ELISA) for the detection of APAs. APAs were measured by ELISA and confirmed by Western blot analysis in sera from patients with endocrine disorders. APAs were detected frequently in patients with autoimmune thyroiditis, insulin-dependent diabetes mellitus (IDDM), or pituitary dwarfism. Circulating APAs were detected in 18% of patients with autoimmune thyroiditis. Confirmation by Western blot revealed positivity for APAs in the serum of 36% of patients with Hashimoto disease and in 29% of patients with Graves disease. Notably, 39% of patients with IDDM were also positive for APAs by ELISA. The identification of APAs by ELISA may be useful in evaluating autoimmune mechanisms involved in patients with multiendocrine disorders.