Biosynthesis of steroid hormones requires a battery of oxidative enzymes located in both mitochondria and endoplasmic reticulum. The rate-limiting step in this process is the transport of free cholesterol from the cytoplasm into mitochondria. Within mitochondria, cholesterol is converted to pregnenolone by an enzyme in the inner membrane called CYP11A1. Pregnenolone itself is not a hormone, but is the immediate precursor for the synthesis of all of the steroid hormones. The following table delineates the enzymes required to synthesize the major classes of steroid hormones.
Catecholamines are produced in chromaffin cells in the medulla of the adrenal gland, from tyrosine , a non-essential amino acid derived from food or produced from phenylalanine in the liver. The enzyme tyrosine hydroxylase converts tyrosine to L-DOPA in the first step of catecholamine synthesis. L-DOPA is then converted to dopamine before it can be turned into noradrenaline. In the cytosol , noradrenaline is converted to epinephrine by the enzyme phenylethanolamine N-methyltransferase (PNMT) and stored in granules. Glucocorticoids produced in the adrenal cortex stimulate the synthesis of catecholamines by increasing the levels of tyrosine hydroxylase and PNMT.  
Depletion and dysregulation of adrenal hormones such as cortisol and adrenaline are the primary symptomatic drivers of Adrenal Fatigue and crashes. Repeated crashes over time will invariably further weaken the adrenal glands. While the intensity of each crash will increase as Adrenal Fatigue increases, it is not a linear progression clinically. Many in Stage 1 and Stage 2 Adrenal Fatigue are not aware of their impending problems. Their daily activities will remain unchanged, as there is sufficient adrenal reserve to compensate for any transient energy low.