What Is Cortisol?
Cortisol, also known as cortisone and hydrocortisone, is a steroid hormone produced in the adrenal glands in response to stress. As such, cortisol is often referred to as the primary "stress hormone." In the body, cortisol is needed to maintain normal physiological processes during times of stress; without cortisol, as discussed in earlier chapters, the body would be unable to respond effectively to stress. Without cortisol, that lion charging at us from the bushes would cause us to do little more than wet our pants and stand there staring (not good). With an effective cortisol metabolism, however, we're primed to run away or do battle, because cortisol secretion releases amino acids (from muscle), glucose (from the liver), and fatty acids (from adipose tissue) into the bloodstream for use as energy. So cortisol is "good"—right? Yes. And no.
Synthetic forms of cortisol, such as prednisone and dexamethasone, are used to treat a wide variety of conditions. They are usually prescribed for their anti-inflammatory and immune-suppressing properties. Cortisol-like drugs can be quite helpful in relieving excessive inflammation in certain skin disorders (Chattem makes an anti-itch skin cream called Cortizone), as well as in inflammatory diseases such as arthritis, colitis, or asthma (the inhalers for which contain corticosteroids). During organ transplantation, cortisol-like drugs are used to suppress the body's immune response, thereby helping to reduce the chance of the body's rejecting the newly transplanted organ. Cortisol-like drugs are also used as replacement therapy for people who have lost function of their adrenal glands (Addison's disease). So, again, cortisol is a "good thing"—right? Yes, but only at certain levels and for a certain period of time.
What Does Cortisol Do?
Cortisol has diverse and highly important effects on regulating aspects of all parts of the body's metabolism of glucose, protein, and fatty acids. The functions of cortisol are also particularly important in when it comes to controlling mood and well-being, immune cells and inflammation, blood vessels and blood pressure, and in the maintenance of connective tissues such as bones, muscles, and skin. Under conditions of stress, cortisol normally maintains blood pressure and limits excessive inflammation. Unfortunately, many people's adrenal stress response overreacts by secreting too much cortisol—with devastating consequences. Cortisol and related corticoids are also known as glucocorticoids, a term that, as was pointed out in the preceding chapter, is derived from early scientific observations that these hormones are intimately involved in glucose metabolism. Cortisol is known to stimulate several metabolic processes that collectively serve to increase concentrations of glucose in blood.
These effects include stimulation of gluconeogenesis (conversion of amino acids into glucose), mobilization of amino acids from muscle tissues (to serve as the raw material in gluconeogenesis), inhibition of glucose uptake in muscle and adipose (fat) tissue (which further increases blood-sugar levels), and stimulation of fat breakdown in adipose tissue. Unfortunately, the fatty acids released by lipolysis (fat breakdown) have a detrimental effect on health, as they reduce cellular sensitivity to insulin, a condition that can be a precursor to diabetes. Cortisol also has potent anti-inflammatory and immunosuppressive properties—both of which are important in regulating normal responses of the immune system.