Pituitary Autoimmunity: A Review

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.

Hypothalamic-Pituitary Autoimmunity and Traumatic Brain Injury

Background: Traumatic brain injury (TBI) is a leading cause of secondary hypopituitarism in children and adults, and is responsible for impaired quality of life, disabilities and compromised development. Alterations of pituitary function can occur at any time after the traumatic event, presenting in various ways and evolving during time, so they require appropriate screening for early detection and treatment. Although the exact pathophysiology is unknown, several mechanisms have been hypothesized, including hypothalamic-pituitary autoimmunity (HP-A). The aim of this study was to systematically review literature on the association between HP-A and TBI-induced hypopituitarism. Major pitfalls related to the HP-A investigation were also discussed. Methods: The PubMed database was searched with a string developed for this purpose, without temporal or language limits, for original articles assessing the association of HP-A and TBI-induced hypopituitarism. Results: Three articles from the same group met the inclusion criteria. Anti-pituitary and anti-hypothalamic antibodies were detected using indirect immunofluorescence in a significant number of patients with acute and chronic TBI. Elevated antibody titer was associated with an increased risk of persistent hypopituitarism, especially somatotroph and gonadotroph deficiency, while no correlations were found with clinical parameters. Conclusion: HPA seems to contribute to TBI-induced pituitary damage, although major methodological issues need to be overcome and larger studies are warranted to confirm these preliminary data.

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.

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

BACKGROUND

Lymphocytic hypophysitis is a disorder of the pituitary gland that presents as a sellar mass lesion and/or hypopituitarism. It causes pituicyte destruction and hypopituitarism and is speculated to have an autoimmune basis.

DIAGNOSIS

Lymphocytic hypophysitis should be considered in the differential diagnosis of pituitary masses and/or hypopituitarism in females who are pregnant or in the early postpartum period, especially in cases associated with other autoimmune diseases or unusual patterns of hormone deficiencies. A definitive diagnosis requires tissue biopsy. A presumptive clinical diagnosis can be made based on a history of gestational or postpartum hypopituitarism, a contrast-enhancing sellar mass with imaging features characteristic of lymphocytic hypophysitis, a pattern of pituitary hormone deficiency with early loss of adrenocorticotrophic hormone and thyroid-stimulating hormone unlike that typically found with macroadenomas, relatively rapid development of hypopituitarism and a degree of pituitary failure disproportionate to the size of the mass. Symptoms resulting from partial or panhypopituitarism occur in approximately 80% of cases and multiple deficiencies are found in approximately 75% of cases.

MANAGEMENT

Appropriate management remains controversial. Corticosteroid therapy has been advocated as a means of attenuating inflammation, but given the uncertainty of its efficacy and the known adverse effects, such therapy does not seem justified for most patients. The optimal surgical strategy involves partial resection of the mass to decompress the surrounding structures. All patients with lymphocytic hypophysitis require appropriate replacement therapy for deficient hormones. Long-term follow-up is mandatory to monitor for the development of other hormonal deficits.

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.

Pituitary antibodies and lymphocytic hypophysitis

Lymphocytic hypophysitis (LYH) is a pituitary disease which can cause headache, changes in visual field and pituitary dysfunction. The clinical, histopathological and morphological findings and its association with other autoimmune disorders allow LYH to be included among the autoimmune diseases. Pituitary trans-sphenoidal biopsy is thought to be the diagnostic gold standard for LYH, even if some morphological findings on hypothalamic-pituitary magnetic resonance imaging (MRI) can suggest the occurrence of this disease. Despite the fact that organ-specific antibodies are good markers of many autoimmune endocrine diseases, the pathogenetic and diagnostic roles of anti-pituitary antibodies (APAs) in LYH are still under discussion. In fact, several methods have been used to detect APAs, but the conflicting results from different methods have impaired the clinical relevance of these antibodies. Recently, APAs have been detected by an immunofluorescence method in patients with selective idiopathic hypopituitarism (particularly in those with growth-hormone deficiency) and in adults with autoimmune endocrine diseases. The results suggest that only when they are present at high titres may they be considered a good marker of pituitary involvement, and in particular of growth-hormone-producing cells.

Lymphocytic hypophysitis: late recurrence following successful transsphenoidal surgery

Lymphocytic hypophysitis (LH) is an inflammatory dis-ease of the anterior pituitary. The varying clinical presentation and the short-term outcome of LH have been extensively described in several case reports or small cohort studies. However, little is known about the long-term outcome of this disease. It is currently believed that if left untreated it may run a self-limited course followed by full resolution of the mass with or without persisting pituitary failure. We describe a 29-yr-old female who presented with secondary amenorrhea, headaches, visual defects, and a pituitary mass, which was removed by transsphenoidal surgery. Histology was consistent with the diagnosis of LH. Following surgery the patient demonstrated a gradual recovery of gonadotroph function with restoration of menses and a successful pregnancy. However, 3 yr after delivery and 6 yr following her initial presentation she developed amenorrhea, headaches, and a pituitary mass. Institution of steroid therapy resulted in resolution of the pituitary mass. In summary, this case illustrates that similarly to many other disorders of autoimmune origin LH may run a fluctuating course and late recurrence is possible even after the successful removal of the inflammatory mass, thus necessitating long-term follow-up of these patients.

Lymphocytic hypophysitis

Lymphocytic hypophysitis is a rare but important cause of pituitary hypofunction which predominantly affects young women in the peripartum period. It is believed to be an autoimmune disorder with an association with other autoimmune disorders and expression of anti-pituitary cytosolic and anti-nuclear antibodies. Clinically, it presents most frequently with symptoms and signs attributable to pituitary hypofunction, headache, visual disturbance and amenorrhoea. It is difficult to distinguish lymphocytic hypophysitis from a pituitary adenoma on pre-operative imaging and definitive diagnosis rests on histology which classically demonstrates destruction of anterior pituitary acini by an inflammatory infiltrate rich in plasma cells and T lymphocytes. Surgical management therefore plays a crucial role to obtain a histological diagnosis and to relieve pressure effects on the optic apparatus in patients with visual disturbances.

[Idiopathic granulomatous hypophysitis. Morphological and immunohistochemical study of a case]

Inflammatory diseases of the pituitary gland constitute a group of interest because of their scarce frequency, because the disorder presents with symptoms of hypopituitarism and expanding sellar mass and because of their therapeutics implications. We present one case of idiopathic granulomatous hypophysitis, in a 55-years-old patient with daily headaches, panhypopituitarism and a sellar mass lesion. Granulomatous hypophysitis is characterized by granulomas with epithelioid histiocytes and multinucleated giant cells but also shows lymphocyte collections. With respect to immunohistochemistry our results show histiocytes (CD68+) and an heterogeneous inflammatory infiltrate (CD45RO+ y CD20+). We analyze the differential diagnosis with another granulomatous processes, infectious or not infectious, and with the histiocytosis. We examine the possible relation with the lymphocytic hypophysitis.

Granulomatous hypophysitis due to Wegener's granulomatosis

We describe the MR image findings in a case of granulomatous hypophysitis due to Wegner's granulomatosis. A high index suspicion of hypophysitis based on imaging findings allowed successful medical management and helped avoid surgery. The MR imaging features included a thickened stalk, a diffusely and uniformly enlarged gland, a normal size or minimally enlarged sella, and enhancement of the optic chiasm.

Lymphocytic and granulomatous hypophysitis: experience with nine cases

OBJECTIVE

Lymphocytic hypophysitis and granulomatous hypophysitis are rarely encountered. The aim of this study was to demonstrate their clinical peculiarities among pituitary disorders and to provide an approach for their clinical management.

METHODS

In a retrospective study, we reviewed our surgical experience with nine patients harboring hypophysitis. The series included six cases of lymphocytic hypophysitis, two cases of granulomatous hypophysitis, and one case with evidence of coexisting lymphocytic and granulomatous hypophysitis.

RESULTS

A striking similarity of clinical signs was found for our nine patients. Headache or aseptic meningitis, thickening of the sphenoid sinus mucosa, pituitary stalk enlargement, and tongue-shaped extension of the lesion along the basal hypothalamus were characteristic signs. Lymphocytic hypophysitis was not associated with pregnancy in any of the seven cases. No recurrence has been observed in six cases with total removal of the inflammatory tissue.

CONCLUSION

Lymphocytic hypophysitis and granulomatous hypophysitis represent related inflammatory disorders. Their conspicuous clinical features frequently allow preoperative diagnosis of hypophysitis. In view of their sometimes insidious clinical course, early surgical exploration is justified.

Hypophysitis in surgical and autoptical specimens

We present the clinical and histological findings of 11 cases of inflammatory anterior pituitary lesions, 8 of which were obtained during surgery and 3 of which were obtained from autopsies. Additionally, we extended the conventional classification of pituitary inflammatory disease by the new entity " secondary hypophysitis". Of the surgically obtained specimens 5 consisted of inflammatory extension into the pituitary gland out of the surrounding tissue. In all of these patients the inflammation originated from an additional tumor in the sellar region (4 craniopharyngiomas, 1 prolactinoma). These will be referred to as "secondary hypophysitis", an entity which has not yet been mentioned in the literature. Of the remaining 6 cases, 2 were granulomatous hypophysitis, 2 pituitary abscesses, 1 lymphocytic hypophysitis, and 1 showed extensive scarring of the anterior pituitary lobe due to preceeding lymphocytic hypophysitis. At histological examination the basic structure of the anterior pituitary was maintained in all cases. Relative counts of hormone-producing cells were normal. In secondary hypophysitis, the affected area was composed of fibrous tissue and granulation tissue. B and T lymphocytes were present in equal amounts. Granulomas were not found. Inflammatory infiltrates, granulation tissue and fibroses were seen in different proportions. Based on our results and three other cases reported in the literature so far, we think that the presently used classification of pituitary inflammatory diseases lacks an entity which describes a non-abscess-forming inflammation of the pituitary gland originating from an associated pathological process. Therefore, we introduced the term secondary hypophysitis to describe this fourth entity of pituitary inflammatory disease.

The anterior pituitary lobe in patients with cystic craniopharyngiomas: three cases of associated lymphocytic hypophysitis

Specimens of the anterior pituitary lobe were investigated histologically in 28 craniopharyngioma patients operated on trans-sphenoidally. The pituitary glands in 3 patients revealed lymphocytic invasion giving a histological appearance typical of lymphocytic hypophysitis (incidence: 11%). At follow-up examination all three patients with associated lymphocytic hypophysitis had complete pituitary insufficiency, whereas only 36% of the craniopharyngioma patients without associated lymphocytic hypophysitis were in this poor postoperative endocrine state. The phenomenon of associated lymphocytic hypophysitis in craniopharyngioma patients has not been reported so far. This might be due to the fact that investigators have failed to systematically examine the anterior pituitary lobe in craniopharyngioma patients. The 60 cases of lymphocytic hypophysitis reported in the literature occurred, for the most part, in women during late pregnancy or shortly after delivery. An auto-immune origin is assumed in this type of inflammation. In contrast to this pathophysiological mechanism, we assume a local induction of inflammation resulting from the craniopharyngioma cyst in our 3 patients.

Preoperative diagnosis of lymphocytic hypophysitis (adenohypophysitis) unresponsive to short course dexamethasone: case report

Lymphocytic hypophysitis (adenohypophysitis) is a rare lymphocytic infiltration of the pituitary gland that usually occurs during pregnancy. Because of its rarity, it has seldom been diagnosed preoperatively, and no trials of therapeutic treatment have been reported to date. We describe a 29-year-old woman with a pituitary mass and visual-field defects during pregnancy. The patient's pituitary profile revealed an abnormal thyroid axis and relatively low prolactin for her stage of pregnancy. This finding suggested adenohypophysitis, and the patient was given a trial course of dexamethasone. The progression of the visual-field defects, however, indicated that the steroids, both in dosage and duration, were not effective. Thus, the patient underwent a partial hypophysectomy for decompression. The pathology report confirmed adenohypophysitis, and steroids were continued for the remainder of the pregnancy, with slow resolution of the visual-field defects to normal. This report is the first case of adenohypophysitis where the diagnosis was suspected preoperatively, and a trial course of steroids was given. The steroids at the dosage and duration used were not effective. Further evaluation of the use of steroids in this disease is warranted.

Lymphocytic adenohypophysitis

Lymphocytic adenohypophysitis (LAH) is an uncommon disorder in the spectrum of pituitary disease. Twenty-three cases proven by biopsy or at autopsy have been reported since 1962. We report 2 further cases and review the etiology, immunology and pathology of the disease. The diagnosis should be considered in a female patient who presents during the post-partum period with the clinical picture of a non-functional or prolactin cell pituitary adenoma and evidence of hypopituitarism.

Antigonadotropic cell antibodies in the serum of cryptorchid children and infants and of their mothers

An indirect immunofluorescence test allowed us to study circulating antigonadotropin-cell antibodies in patients with cryptorchidism. Antigonadotropin-cell activity was found in the serum in 14 of 23 cryptorchid boys aged 1 to 11 years and in 12 of 23 infants aged 1 to 3 months; in most of them the antibodies persisted during short-term follow-up. Results of paired study of the mother and infant were concordant in 14 of 15 cases. No such antibodies were found in 24 control male children. These data support the possible role of pituitary autoimmunity in the child and the mother as a factor in testicular maldescent. We found no correlation between the presence or absence of antibodies and the partial luteinizing hormone-Leydig cell deficiency usually found in cryptorchidism.

Histological classification of pituitary disease

Morphological features of pituitary disease are classified according to increased and decreased hormone production to allow clinical correlation with pathological processes. Increased hormone synthesis and secretion may be due to pituitary adenomas or carcinomas derived from the five hormone-secreting cell types, or to extrapituitary stimuli causing hypertrophy and hyperplasia of those cells. Various tumour-like conditions can mimic functioning adenomas. Rarely, no lesion is detected and intrinsic abnormalities of adenohypophyseal cells are implicated. Hypopituitarism can be selective or generalized. Diffuse hormone deficiency is usually attributable to tissue destruction by tumours, inflammatory or infiltrative conditions or vascular lesions. Congenital abnormalities of pituitary development may result in hypophyseal dysfunction. Hypothalamic abnormalities may cause generalized hypopituitarism or may involve only selective releasing factors and hormones. Feedback inhibition and receptor abnormalities may be implicated in pituitary hypofunction, and selective deficiencies may be the result of genetic abnormalities, immune reactions or toxic damage to one cell type.

Lymphocytic adenohypophysitis of pregnancy simulating a pituitary adenoma: a distinct pathological entity. Report of two cases

Diffuse lymphocytic infiltration of the adenohypophysis occurring in temporal relation to pregnancy was found in two patients, each of whom had an intrasellar mass with suprasellar extension that caused compression of the optic chiasm. The pathology and etiology of this lesion is discussed. This entity should be considered when evaluating patients with a pituitary mass lesion that presents in temporal association to pregnancy, particularly if there is evidence of hypopituitarism rather than a hypersecreting, endocrine-active adenoma.

The association of diabetes insipidus with hypoparathyroidism. Addison's disease and mucocutaneous candidiasis

A case of central diabetes insipidus is reported in association with idiopathic hypoparathyroidism, adrenal failure and mucocutaneous candidiasis. The diabetes insipidus was recognised at the same time as the discovery of aldosterone and cortisol deficiency, and occurred several years after the initial onset of mucocutaneous candidiasis and hypocalcaemia. Control of the diabetes insipidus was achieved initially with nasal aqueous lysine vasopressin and later with desmopressin. The development of diabetes insipidus may be a further aspect of endocrine secretory failure associated with idiopathic hypoparathyroidism.