Hypophysitis

Hypophysitis is defined as inflammation of the pituitary gland that is primary or secondary to a local or systemic process.

AKA Autoimmune hypophysitis

Lymphocytic adenohypohysitis and lymphocytic infundibulo neurohypophysitis are rare autoimmune mediated diseases of the anterior and posterior pituitary, respectively. Lymphocytic hypophysitis is a relatively rare autoimmune disease defined by lymphocytic infiltration to the pituitary.

Most hypophysitis causes are autoimmune, but other etiologies include inflammation secondary to sellar tumors or cysts, systemic diseases, and infection or drug-induced causes. Novel pathologies such as immunoglobulin G4-related hypophysitis, immunotherapy-induced hypophysitis, and paraneoplastic pituitary-directed autoimmunity are also included in a growing spectrum of this rare pituitary disease.

Patients with hypophysitis typically present with headaches, some degree of anterior and/or posterior pituitary dysfunction.

Enlargement of the pituitary gland and/or stalk, as determined by imaging.

Typical magnetic resonance imaging reveals stalk thickening and homogenous enlargement of the pituitary gland; however, imaging is not always specific. Diagnosis can be challenging, and ultimately, only a pituitary biopsy can confirm hypophysitis type and rule out other etiologies. A presumptive diagnosis can be made often without a biopsy. Detailed history and clinical examination are essential, notably for signs of underlying etiology with systemic manifestations.

In the majority of patients, Hypophysitis can be reliably identified by characteristic clinical signs and symptoms, obviating histological confirmation. The diagnostic approach should be standardized ¹⁾.

Differential diagnosis is broad (including primary tumors, metastases, and lymphoproliferative diseases) and multifaceted.

Autoimmune hypophysitis (AH) mimics the more common nonsecreting pituitary adenomas and can be diagnosed with certainty only histologically. Approximately 40% of patients with AH are still misdiagnosed as having pituitary macroadenoma and undergo unnecessary surgery. MR imaging is currently the best noninvasive diagnostic tool to differentiate AH from nonsecreting adenomas, though no single radiologic sign is diagnostically accurate.

In a case control study of from the Department of Neurosurgery, Georg August University Göttingen, Germany, 402 patients, which compared the presurgical pituitary MR imaging features of patients with nonsecreting pituitary adenoma and controls with AH. MR images were compared on the basis of 16 morphologic features besides sex, age, and relation to pregnancy.

Only 2 of the 19 proposed features tested lacked prognostic value. When the other 17 predictors were analyzed jointly in a multiple logistic regression model, 8 (relation to pregnancy, pituitary mass volume and symmetry, signal intensity and signal intensity homogeneity after gadolinium administration, posterior pituitary bright spot presence, stalk size, and mucosal swelling) remained significant predictors of a correct classification. The diagnostic score had a global performance of 0.9917 and correctly classified 97% of the patients, with a sensitivity of 92%, a specificity of 99%, a positive predictive value of 97%, and a negative predictive value of 97% for the diagnosis of AH.

This new radiologic score could be integrated into the management of patients with AH, who derive greater benefit from medical as opposed to surgical treatment ²⁾.

Hormone replacement and, in selected cases, careful observation are advised with imaging follow-up. High-dose glucocorticoids are initiated mainly to help reduce the mass effect. A response may be observed in all auto-immune etiologies, as well as in lymphoproliferative diseases, and, as such, should not be used for differential diagnosis. Surgery may be necessary in some cases to relieve mass effects and allow a definite diagnosis. Immunosuppressive therapy and radiation are sometimes also necessary in resistant cases ³⁾. ^{4) 5) 6)}

MRI of the Pituitary Gland By Jean-François Bonneville, Fabrice Bonneville, Françoise Cattin, Sonia Nagi

This clinically oriented book will familiarize the reader with all aspects of the diagnosis of tumors and other disorders of the pituitary gland by means of magnetic resonance imaging (MRI). The coverage includes acromegaly, Cushing’s disease, Rathke cleft cysts, prolactinomas, incidentalomas, Clinically non-functioning pituitary adenomas, other lesions of the sellar region, hypophysitis, and central diabetes insipidus. Normal radiologic anatomy and the numerous normal variants are described, and guidance is also provided on difficulties, artifacts, and other pitfalls. The book combines concise text and high-quality images with a question and answer format geared toward the needs of the practitioner. MRI is today considered the cornerstone in the diagnosis of diseases of the hypophyseal-hypothalamic region but the relatively small size of the pituitary gland, its deep location, the many normal anatomic variants, and the often tiny size of lesions can hinder precise evaluation of the anatomic structures and particularly the pituitary gland itself. Radiologists and endocrinologists will find MRI of the Pituitary Gland to be full of helpful information on this essential examination, and the book will also be of interest to internists and neurosurgeons.