Median Eminence Dopaminergic Nerve Terminals: A Novel Target in Autoimmune Polyendocrine Syndrome?

Context: Autoantibodies to adenohypophyseal endocrine cells or to vasopressin neurohypophyseal neurons have long been known. Conversely, autoimmune targeting of further hypothalamic-hypophyseal structures, such as the blood-brain barrier-deprived median eminence, has been little studied. Objective and Methods: We studied a case of autoimmune polyendocrine syndrome type I with GH secretory deficiency, a distinctly rare event in autoimmune polyendocrine syndrome type I. We used rat and bovine tissue substrates to study autoantibodies against hypothalamic-hypophyseal nerve structures and endocrine cells. Results: In the study case, circulating autoantibodies selectively decorated median eminence dopaminergic nerve terminals, as well as pituitary gonadotropes, but not GHRH nerve terminals or pituitary somatotropes. Such autoantibodies appeared de novo in parallel with the onset of GH secretory deficiency, whereas no median eminence labeling was found in patients suffering of idiopathic GH deficiency (n = 7) or in healthy controls (n = 23). Conclusions: The pathophysiological significance of our patient’s autoantibodies remains to be confirmed. Nonetheless, the heterogeneous neuroendocrine structures of the median eminence are pointed out as potential immune targets, relevant to autoimmune polyendocrinopathy, as well as to a wide range of other conditions.