Diagnosis and Classification of Autoimmune Hypophysitis

Autoimmmune hypophysitis (AH) is the consequence of an immune-mediated inflammation of the pituitary gland. The initial pituitary enlargement, secondary to infiltration and oedema, can evolve to remission, for spontaneous or pharmacological resolution of the inflammation, or evolve to progressive diffuse destruction with gland atrophy for fibrotic replacement, thus leading to various degrees of pituitary dysfunction. The autoimmune process against the pituitary gland is made evident by the appearance of circulating autoantibodies (APA), mainly detected by indirect immunofluorescence on cryostatic sections of human or primate pituitary. Among the target autoantigens recognized by APA are alpha-enolase, gamma-enolase, the pituitary gland specific factors (PGSF) 1 and 2 and corticotroph-specific transcription factor (TPIT). However, the low diagnostic sensitivity and specificity of APA for AH strongly limit the clinical use of this marker. AH should be considered in the differential diagnosis of non-secreting space-occupying lesions of sella turcica, to avoid misdiagnosis that may lead to an aggressive surgery approach, since endocrine dysfunction and the compressive effect may be transient.