Autoimmune Hypophysitis

Autoimmune hypophysitis is due to an immune-mediated inflammation of pituitary gland. It is also known as lymphocytic hypophysitis and causes pituitary tissue damage with initial pituitary enlargement that can evolve to remission, for spontaneous or pharmacological resolution of the inflammation, or evolve to progressive diffuse destruction with gland atrophy and various degrees of pituitary dysfunction. During the last decades, the spectrum of forms of hypophysitis has broaden, and now, we also recognize granulomatous hypophysitis, xanthomatous hypophysitis, IgG4-related hypophysitis, immune checkpoint inhibitors-induced hypophysitis and other very rare forms. The autoimmune process against the pituitary gland is made evident by the appearance of circulating anti-pituitary autoantibodies (APA), mainly detected by indirect immunofluorescence on cryostatic sections of human or primate pituitary. Several putative target autoantigens have been identified, but the low diagnostic sensitivity and specificity of APA for autoimmune hypophysitis strongly limit the clinical use of their detection. Hypophysitis should always be considered in the differential diagnosis of non-secreting space-occupying lesions of sella turcica.