AVP and myalgic encephalomeyelitis/chronic fatigue syndrome: Several studies found that the response to CRH injection was blunted in ME/CFS patients compared to controls (i.e., ensuing cortisol or ACTH production were lower than in controls) (51, 56, 62), but this was not the case when CRH was combined with desmopressin (a synthetic analog of arginine vasopressin, AVP) which acts synergistically with CRH on the pituitary to stimulate ACTH secretion (52).