Question

Why pigmentation occurs in Primary adrenocortical insufficiency but not in secondary adrenocortical insufficiency?

Answer 1

In primary adrenocortical insufficiency i.e. Addison's disease, there is hypersecretion of ACTH through feedback regulation
Secondary adrenocortical insufficiency itself is caused by deficiency of ACTH
ACTH and MSH are synthesized from Pro-opiomelanocortin (POMC)