Pt has signs and Sx of hypercortisol. Low/normal ACTH favors elevated cortisol independent of ACTH, confirmed by lack of response to dexamethasone suppression. Zona fasciculata is origin of cortisol production.
champagnesupernova3They tried to confuse us saying both low dose and high dose dexamethasone didnt suppress it. But when ACTH is low you dont even need to do high dose dexamethasone test. The high dose is only to differentiate between Pituitary adenoma and ectopic ACTH production+8
azharhu786They got me on that question as well. I thought it was ectopic ACTH production due to some paraneoplastic syndrome and this is why Low/ high dose dexa is unable to suppress it. +1
skonysHigh dose dexamethasone would rule out Cushing Disease because the adenoma responds to cortisol, just at a higher set point. But even before that, the ACTH is low, so it can't be A or B because they would be high. The problem is downstream; low ACTH -> body saying "NOO! Stop! You can't just keep making cortisol!" but the zona fasciculata is like "haha, negative feedback go brrrrr"+2
utap2001Low dose dexamethsone is just for screening of Cushing syndrome(adenoma, ectopic, adrenal). For rule out normal person. High dose dexa is used to D/D adenoma and ectopic. +
submitted by โergogenic22(401)
Pt has signs and Sx of hypercortisol. Low/normal ACTH favors elevated cortisol independent of ACTH, confirmed by lack of response to dexamethasone suppression. Zona fasciculata is origin of cortisol production.