Types of hypophysitis
Hypophysitis is a general term used to describe chronic inflammation of the pituitary gland and can be classified according to the anatomic location of the pituitary involvement, the cause, and the histopathologic appearance.
On the basis of clinical, radiologic, and pathologic findings, the condition is classified as adenohypophysitis, infundibuloneurohypophysitis, and panhypophysitis. Depending on the etiology, it can be considered primary or secondary, the latter having a clear cause.
Histopathologically, it is classified as lymphocytic, granulomatous, plasmacytic (immunoglobulin G4 [IgG4]–associated), and xanthomatous.
Lymphocytic hypophysitis, the most common form, is characterized by a marked infiltration of lymphocytes that populate the pituitary gland both diffusely and occasionally in focal clusters.
The lymphocytes are accompanied by scattered plasma cells, eosinophils, and fibroblasts, and by fibrosis in later stages. It is three times more common in women than in men and uniquely presents in association with late pregnancy and the early postpartum period in about 40% of affected women. Hypophysitis may also occur as a complication of anti–cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) immunotherapy, mostly with ipilimumab (Yervoy), which is used to treat melanoma.
Patients usually present with the triad of headaches, hypopituitarism, and pituitary enlargement within 8 to 10 weeks after beginning treatment. This complication affects 15% of patients treated with ipilimumab.