Originally Posted by muskimd
Yes, since ACTH produces a precursor for MSH - POMP - hence you see pigmentation is addisons disease
From what I remember POMC (proopiomelanocortin)is large molecule made in anterior pituitary and it is a precursor of many molecules,one of them is ACTH and MSH(there is 2 MSH made from POMC: alpha and beta-MSH,both stimulate melanocytes but one made by further cleavage of ACTH to alpha-MSH,beta MSH made from cleavage of lipotropin:also molecule made from POMC) .
In Cushing disease(NOT syndrom-for example in SC lung carcinoma which also cause Cushing, there will not be hyper- pigmentation) there is increase production of POMC due to loss of negative inhibition by cortisol,in Addison disease on the other hand there is low cortisol so there is increased production of POMC which cleaved to ACTH and than MSH etc..
So it will be in BOTH Addison and Cushing disease hyperpigmentation.