[A Novel Clinical Entity "Anti-PIT-1 Antibody Syndrome"--Autoimmunity against a Transcription Factor]

Autoimmunity against the pituitary has been observed in patients with hypophysitis. Although various autoantibodies against pituitary proteins have been reported, it is known that most of them are markers for the disease. Recently, a unique autoantibody against pituitary transcription factor PIT-1 (POU1F1) was detected in patients with an acquired combined pituitary hormone deficiency characterized by a specific defect in growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH). The antibody has been suggested to be involved in the pathogenesis because PIT-1 is an essential transcription factor that plays a role in the differentiation and maintenance of GH-, PRL-, and TSH-producing cells and mutations in the PIT-1 gene, resulting in a specific defect in these hormones. This syndrome was found to be a novel clinical entity; therefore, it was named 'anti-PIT-1 antibody syndrome'. Circulating anti-PIT-1 antibody and various autoantibodies were detected with multiple endocrine organopathy, meeting the definition of autoimmune polyglandular syndrome. Mechanistically, cytotoxic T lymphocytes that specifically react with PIT-1 protein play an important role in the development of this syndrome. In this review, we discuss the clinical aspects and pathophysiology of anti-PIT-1 antibody syndrome.