Recurrent Cushing's disease with low adrenal androgen production.

A 33 year old woman presented with recurrent Cushing's disease 4 years after complete remission induced by pituitary surgery. On relapse she exhibited the unusual pattern of elevated indices of cortisol secretion with markedly suppressed serum DHEA-S; urinary 17-ketosteroid excretion was also below the normal range. Biochemical testing was otherwise consistent with ACTH-mediated hypercortisolism, and adrenal histopathology showed bilateral hyperplasia with no evidence of tumor. This case illustrates that serum DHEA-S is not an infallible guide to the differential diagnosis of Cushing's syndrome, and it supports the existence of a pituitary-secreted adrenal androgen stimulating factor that is distinct from ACTH.