During the past month I also have been suffering with low cortisol ( 214 nmol/l ). I also have low ferritin at the moment. That said my morning serum cortisol almost doubled ( to 400 nmol/l ) when I reduced my Enanthate dose.
Still it may very well be that correcting low iron levels could improve the function of the HPA-axis. Here's a quote from mariano that seems to give support to all this:
"Poor nutrition - which is the bulk of modern diets even those that seem nutritious - impairs metabolic function, which in turn impairs the reception of signals from the immune system, nervous system, and endocrine system. For example, iron deficiency or suboptimization, significantly impairs recovery of the HPA Axis. So long as ferritin levels are low, the adrenal can't function well, no matter what the treatment. Low iron also forces a compensatory shift to a stressed nervous system.
Suboptimal nutrition - including the lack of saturated fats and cholesterol in the diet, the lack of complex foods and highly dense nutritious meals - impairs metabolic function. Multiple areas in the world are minerally deficient - leading to minerally deficient vegetables. They look the same but don't have the nutritional value of foods years ago. Fat soluble vitamin deficiencies are very frequent. Vitamin D deficiency is frequent - without Vitamin D, serotonin and dopamine signaling is impaired, insulin resistance worsens, etc. B-vitamin deficiencies prevent thyroid hormone from working."