Cutler explains that Hg affects cortisol production in the adrenal cortex but not adrenal production in the adrenal medulla. I think he says that Cd does the opposite. This is not a quote so what he actually says might be worded differently. I think I read this in his book Hair Test Interpretation but he touches on it in Amalgam Illness as well in the image around p 32.
By taking the whole adrenal supplement instead of just cortex, there is the likelihood of promoting production of more adrenaline. So many Hg toxic folks already have trouble with anxiety and stress management. The last thing they need is more adrenaline!