Antipituitary antibodies in patients with pituitary abnormalities and hormonal deficiency

Neuroimmunoendocrinology of SARS-CoV 2 Infection

This review is aimed at illustrating and discussing the neuroimmune endocrinological aspects of the SARS-CoV-2 infection in light of the studies on this topic that have so far appeared in the literature. The most characteristic findings and pending controversies were derived by PubMed and Scopus databases. We included original and observational studies, reviews, meta-analysis, and case reports. The entry of the coronavirus into susceptible cells is allowed by the interaction with an ecto-enzyme located on human cells, the angiotensin-converting enzyme 2 (ACE2). SARS-CoV-2 also targets the central nervous system (CNS), including hypothalamic-pituitary structures, as their tissues express ACE2, and ACE2 mRNA expression in hypothalamus and pituitary gland cells has been confirmed in an autoptic study on patients who died of COVID 19. SARS-CoV-2 infection may cause central endocrine disorders in acute phase and in post-COVID period, particularly due to the effects of this virus at CNS level involving the hypothalamic-pituitary axis. The aggression to the hypothalamus-pituitary region may also elicit an autoimmune process involving this axis, responsible consequently for functional disorders of the satellite glands. Adrenal, thyroid and gonadal dysfunctions, as well as pituitary alterations involving GH and prolactin secretions, have so far been reported. However, the extent to which COVID-19 contributes to short- and long-term effects of infection to the endocrine system is currently being discussed and deserves further detailed research.

Antibodies Against Hypothalamus and Pituitary Gland in Childhood-Onset Brain Tumors and Pituitary Dysfunction

Purpose: To detect the presence of antipituitary (APA) and antihypothalamus antibodies (AHA) in subjects treated for brain cancers, and to evaluate their potential association with pituitary dysfunction. Methods: We evaluated 63 patients with craniopharyngioma, glioma, and germinoma treated with surgery and/or radiotherapy and/or chemotherapy at a median age of 13 years. Forty-one had multiple pituitary hormone deficiencies (MPHD), six had a single pituitary defect. GH was the most common defect (65.1%), followed by AVP (61.9%), TSH (57.1%), ACTH (49.2%), and gonadotropin (38.1%). APA and AHA were evaluated by simple indirect immunofluorescence method indirect immunofluorescence in patients and in 50 healthy controls. Results: Circulating APA and/or AHA were found in 31 subjects (49.2%) and in none of the healthy controls. In particular, 25 subjects out of 31 were APA (80.6%), 26 were AHA (83.90%), and 20 were both APA and AHA (64.5%). Nine patients APA and/or AHA have craniopharyngioma (29%), seven (22.6%) have glioma, and 15 (48.4%) have germinoma. Patients with craniopharyngioma were positive for at least one antibody in 39.1% compared to 33.3% of patients with glioma and to 78.9% of those with germinoma with an analogous distribution for APA and AHA between the three tumors. The presence of APA or AHA and of both APA and AHA was significantly increased in patients with germinoma. The presence of APA (P = 0.001) and their titers (P = 0.001) was significantly associated with the type of tumor in the following order: germinomas, craniopharyngiomas, and gliomas; an analogous distribution was observed for the presence of AHA (P = 0.002) and their titers (P = 0.012). In addition, we found a significant association between radiotherapy and APA (P = 0.03). Conclusions: Brain tumors especially germinoma are associated with the development of hypothalamic-pituitary antibodies and pituitary defects. The correct interpretation of APA/AHA antibodies is essential to avoid a misdiagnosis of an autoimmune infundibulo-neurohypophysitis or pituitary hypophysitis in patients with germinoma.

Revisitation of autoimmune hypophysitis: knowledge and uncertainties on pathophysiological and clinical aspects

PURPOSE

This publication reviews the accepted knowledges and the findings still discussed on several features of autoimmune hypophysitis, including the most recently described forms, such as IgG4 and cancer immunotherapy- related hypophysitis.

METHODS

The most characteristic findings and the pending controversies were derived from a literature review and previous personal experiences. A single paragraph focused on some atypical examples of the disease presenting under confounding pretences.

RESULTS

Headache, visual field alterations and impaired pituitary secretion are the most frequent clinical findings of the disease. Pituitary biopsy, still considered the gold diagnostic standard, does not always receive consent from the patients. The role of magnetic resonance imaging is limited, as this disease may generate images similar to those of other diseases. The role of antipituitary and antihypothalamus antibodies is still discussed owing to methodological difficulties and also because the findings on the true pituitary antigen(s) are still debated. However, the low sensitivity and specificity of immunofluorescence, one of the more widely employed methods to detect these antibodies, may be improved, considering a predetermined cut-off titre and a particular kind of immunostaining.

CONCLUSION

Autoimmune hypophysitis is a multifaceted disease, which may certainly be diagnosed by pituitary biopsy. However, the possible different clinical, laboratory and imaging features must be considered by the physician to avoid a misdiagnosis when examining a possibly affected patient. Therapeutic choice has to be made taking into account the clinical conditions and the degree of hypothalamic-pituitary involvement, but also considering that spontaneous remissions can occur.

Use of serum pituitary antibodies to improve the diagnosis of hypophysitis

Lymphocytic hypophysitis is characterized by an extensive infiltration of lymphocytic cells. Pituitary biopsy is the gold diagnostic standard for lymphocytic hypophysitis but the disease occurs with moderate or without pituitary enlargement. The role of antipituitary antibodies (APA) in autoimmune hypophysitis is still discussed due to various methodological difficulties. Indirect immunofluorescence, a widely employed method to detect APA at this time produces highly variable results due to the use of human or animal pituitary substrates. For many years the authors have conducted a re-evaluation of APA by immunofluorescence in patients with other autoimmune diseases and in patients with apparently idiopathic hypopituitarism, using pituitary from young baboons as substrate but considering a predetermined cut-off of the titer and immunofluorescence pattern. This procedure allowed us to find out those with autoimmune pituitary impairment and to foresee the kind of future hypopituitarism in those with pituitary function still normal. Moreover, in APA positive patients, the use of a second step of a double immunofluorescence method allowed identification of the pituitary cells targeted by APA, verifying the correspondence with the kind of hypopituitarism, also when present in subclinical stage. However, to carry out an international workshop comparing the detection of APA by immunofluorescence using different substrates could contribute to verify the best choice to improve the sensitivity and specificity of this method.

Prevalence of antipituitary antibodies in acromegaly

Acromegaly is a rare disorder due to an excessive production of growth hormone (GH), typically caused by a GH-secreting pituitary adenoma. Anti-pituitary antibodies (APAs) are often seen in patients with different kinds of pituitary pathologies. Because GH has been proposed as a possible antigen recognized by such antibodies, the prevalence of APAs may be higher in conditions characterized by excessive GH secretion. The primary aim of this study was to compare the prevalence of APAs in patients with acromegaly and in controls with other types of pituitary tumors and healthy subjects. Secondary aim was to characterize the pituitary cells targeted by the APAs. Thirty eight acromegaly patients and 215 controls, including 38 patients with prolactinomas, 64 with non-functioning pituitary adenomas (NFPA), and 113 healthy subjects were enrolled in the study. All subjects were tested for APAs using indirect immunofluorescence. Target cells recognized by APAs were identified by double staining immunofluorescence. APAs were significantly more prevalent in acromegaly cases than in healthy controls (10.5% vs. 1.8%, P < 0.05). This prevalence was similar to that found in patients with prolactinomas (7.9%) and NFPA (12.5%). Among APAs-positive subjects, antibodies recognizing somatotrope cells were more common in acromegaly cases than in healthy controls (3/4 vs. 0/113, P < 0.0001), but had similar frequencies in NFPA (2/8) and prolactinomas (1/3). APAs are more frequently found in patients with pituitary adenomas than healthy subjects, with no significant difference among the tumor types studied. GH-secreting cells could represent a target of the autoimmune response.

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.

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.

Characterization of antipituitary antibodies targeting pituitary hormone-secreting cells in idiopathic growth hormone deficiency and autoimmune endocrine diseases

OBJECTIVE

In order to investigate whether somatotrophs are the target of antipituitary antibodies (APA) in adult patients with growth hormone deficiency (GHD), we studied the sera of 37 APA positive patients.

PATIENTS

Patients were grouped as follows: nine patients with APA at high titre (> 1 : 8) affected by apparently idiopathic GHD; four of them (group 1a) with isolated GHD diagnosed during childhood and five with GHD diagnosed during adulthood associated with autoimmune endocrine diseases (group 1b), and 28 patients with autoimmune endocrine diseases without pituitary impairment, previously found positive for APA at low titre (1 : 8, group 2).

MEASUREMENTS

APA were evaluated by a four-layer double indirect immunofluorescence technique.

RESULTS

In group 1a patients, APA immunostained exclusively GH-producing cells. In group 1b patients, APA were directed not only to GH- but also to other pituitary hormone-producing cells. In group 2 patients, APA were directed selectively to PRL-producing cells and rarely to some GH-producing cells.

CONCLUSIONS

In the present study, we demonstrated that GH-secreting cells are the target of the autoimmune reaction in autoimmune GHD and that the immunostaining of only the somatotrophs is typical of isolated GHD. In contrast, the finding of diffuse staining of APA indicates the need to search for other autoimmune diseases. Finally, the presence of APA at low titre directed against PRL-secreting cells in patients with autoimmune endocrine diseases in the absence of pituitary impairment, seems to be only a nonspecific marker of pituitary autoimmunity. A longitudinal study would be useful to clarify the relationship between the different pituitary cell involvement and the natural history of pituitary dysfunction in autoimmune hypophysitis.