The information provided by the adrenal cortical steroids: a hypothesis

We present the hypothesis that in vertebrates their closed blood circulation facilitated the evolution of the adrenal cortex as a central processing unit that provides the rest of the body with information on the effect of changes in the blood glucose and sodium levels on the functioning of the mitochondria, and of sodium transporters in the adrenal cortex. When cells in the glomerulosa can no longer increase the synthesis of aldosterone, the message to the body is that a higher level of sodium in the blood may damage the cells. When the fasiculata cells cannot increase the synthesis of glucorticoids, the message to the body is that their mitochondria cannot produce more ATP, and that higher levels of glucose in the blood may harm the organism.