A Novel Clinical Entity of Autoimmune Endocrinopathy: Anti-PIT-1 Antibody Syndrome

Pituitary-specific transcription factor 1 (PIT-1; POU domain, class 1, transcription factor 1 (POU1F1)) is an essential transcription factor for the differentiation of somatotrophs, lactotrophs, and thyrotrophs, and for the expression of growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH). Mutations in PIT-1 cause congenital defects in GH and PRL secretion and severe TSH insufficiency. Anti-PIT-1 antibody syndrome, firstly reported in 2011, is characterized by acquired GH, PRL, and TSH deficiencies without PIT-1 mutation and is associated with the presence of the circulating antibody against PIT-1 protein as a marker. Various autoantibodies are detected with multiple endocrine organopathies in this syndrome; therefore, it meets the criteria of autoimmune polyglandular syndrome. Mechanistically, cytotoxic T lymphocytes specifically reacting with PIT-1 protein play an important role in the development of this syndrome.