Autoantibodies against pituitary proteins in patients with adrenocorticotropin‐deficiency

Abstract

An autoimmune cause of adrenocorticotropin (ACTH)-deficiency is presented, as it is known to be a characteristic feature of lymphocytic hypophysitis, a disease of the pituitary gland considered to be autoimmune. The aim of this study was twofold: (1) to evaluate the occurrence of pituitary autoantibodies and (2) to correlate it to clinical and immunological features in a large group of patients with ACTH-deficiency of possible autoimmune aetiology. Sixty-five patients with ACTH-deficiency and 57 healthy subjects participated in the study. Pituitary autoantibodies were measured by an immunoblotting assay with human pituitary cytosol as antigen. Autoantibodies to a novel 36-kDa pituitary autoantigen were seen in sera from 18.5% (12/65) patients and only 3.5% (2/57) of control subjects (P = 0.0214). When taking only those subjects with strong immunoreactivity into account, the significance was lost; P = 0.3642. Immunoreactivity to a 49-kDa pituitary autoantigen was observed in 21.5% (14/65) of ACTH-deficient patients compared with 8.8% (5/57) of control subjects (P = 0.0910). This 49-kDa pituitary autoantigen has recently been identified as neurone-specific enolase and a candidate marker for neuroendocrine autoimmunity. Clinical parameters in patients with positive versus those with negative pituitary immunoreactivity did not differ. However, autoantibodies to thyroglobulin were positively correlated to immunoreactivity against the 36-kDa pituitary autoantigen (P = 0.014). Our findings of pituitary autoantibodies in patients' sera support the theory that an autoimmune destruction of corticotrophs may be the underlying cause of hormonal deficit in some patients with ACTH-deficiency.