AVP and Hyponatremia: If OXT is only a surrogate marker of SIADH, one can posit that the OXT axonal terminals passively release their neuropeptide at the same time than the AVP axonal terminals, starting early in the days after surgery, but, taking into account the mechanisms of action of AVP (namely an increased insertion but also transcription of water channels into the kidney tubes), the occurrence and nadir of hyponatremia could be delayed 3 days later.