Hypophysitis

Inflammatory disorder of the pituitary gland, often mimicking adenoma.

Causes / types

• Lymphocytic: classic, pregnancy/post-partum, autoimmune.
• IgG4-related.
• Granulomatous: sarcoidosis, TB.
• Drug-related: immune checkpoint inhibitors (e.g. ipilimumab, nivolumab).
• Xanthomatous / mixed (rarer).

Clinical

• Headache, fatigue, visual disturbance.
• Hypopituitarism common; diabetes insipidus more frequent than in adenoma.
• May present with acute/subacute pituitary failure in ICI patients.

Imaging features

• Symmetrical gland enlargement, “plump” pituitary.
• Homogeneous enhancement.
• Thick, non-tapering stalk.
• Posterior pituitary bright spot often lost.
• Can show dural/infundibular enhancement; in ICI-hypophysitis, sometimes a peripheral “ring” of enhancement.

Differential diagnosis

Main ddx = macroadenoma

• Adenoma usually asymmetric, off-midline, more cavernous sinus invasion, snowman shape.
• Hypophysitis favours symmetry + thick stalk + DI.

Management:

High-dose steroids often lead to shrinkage; avoid unnecessary trans-sphenoidal surgery when imaging strongly suggests hypophysitis.