Pituitary autoantibodies

Purpose of reviewThe aim of this article is to review recent advancements in pituitary autoantibody assays. Recent findingsThe newest assay is based on the in-vitro transcription and translation of pituitary specific proteins followed by immunoprecipitation with patient sera. The two proteins, PGSF1a and PGSF2, were identified as pituitary specific from a human pituitary gland cDNA library. Autoantibodies were found in one patient with biopsy proven lymphocytic hypophysitis and seven with suspected hypophysitis, including idiopathic hypopituitarism. Patients with rheumatoid arthritis, especially if rheumatoid factor negative, also had autoantibodies to PGSF1a. An immunoblotting method identified the autoantigen enolase (both α and neuron-specific), as a marker of neuroendocrine autoimmunity but an in-vitro transcription and translation assay has shown that enolase autoantibodies are nonspecific. Enolase autoantibodies have also been found in Sheehan's syndrome. Immunoblotting identified a novel 36 kDa pituitary cytosolic autoantigen in adrenocorticotropin (ACTH) deficiency and pituitary membrane proteins of 68, 49 and 43 kDa in patients with lymphocytic hypophysitis. Indirect immunofluorescence using baboon pituitary has been revisited and somatotroph autoantibodies found in patients with idiopathic growth hormone (GH) deficiency. High titre antibodies were thought to be clinically significant. Enyme-linked immunosorbent assays using human pituitary adenoma cells or rat tissue have identified antibodies in patients with type 1 diabetes, Hashimoto's thyroiditis and various pituitary disorders but not hypophysitis. SummaryThe search for reliable and specific pituitary autoantibody markers continues.