The adrenal cortex is the outer layer of the adrenal gland. It is divided into three distinct "zones," each of which has an independent function. The outermost layer produces mineralocorticoid hormones. The second layer is the largest, comprising 80 percent of the structure. It mainly produces cortisol. The third, innermost layer of the adrenal cortex produces adrenal androgens, a precursor to testosterone and a vital part of the "fight" response of adrenaline.

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