Cortisol

Cortisol helps the body respond quickly and constructively to stress. It also stimulates appetite, boosts energy levels, improves digestion, eases movement in the joints, eases inflammation and pain, soothes allergies, fever, and reactions to toxins, and enhances the immune system (though at excessive doses cortisol actually depresses the immune system). Assuming the correct balance with androgens ("male" hormones like testosterone) is maintained, cortisol might help you live longer.

Cortisol, sometimes called hydrocortisone, comes from the adrenal glands. Casual investigation might lead you to associate cortisol with stress - and, indeed, cortisol levels soar when you are under a great deal of stress. But it is really the anti-stress hormone. It rises under stress because it is actually helping your body handle stress, trying to give you a way to get rid of it. Cortisol frees up your energy reserves at opportune moments. At times of stress, cortisol makes the heart beat faster, increases blood pressure (and so the supply of oxygen and nutrients to all parts of the body), and boosts blood-sugar levels to provide strength and energy. Cortisol drives blood toward strategic parts of the body, including the head, shoulders, trunk, pelvis, and hips - basically preparing you for "fight or flight". These are all short-term responses you need in the moment of greatest stress, though this hormone also works over the long term. Cortisol helps keep you ready for anything and eager for action.

Cortisol stimulates the brain, muscles, heart, and circulatory and respiratory systems. It fights certain forms of cancer (at reasonable doses), like leukemia and certain lymphomas. It also fights jet lag, fatigue, confusion, hypoglycemia, sugar cravings, anxiety, irritability, low mood, "burnout", and low blood pressure. It stimulates the immune system, helping ward off the flu and other viral, bacterial, or parasitic infections as well as cancer.

Humans cannot live without cortisol. Even mild deficiencies can wreak havoc in the body, resulting in hair loss, emaciation, low blood pressure, rapid pulse and/or palpitations in response to the least stress, painful and inflamed joints, and skin problems including eczema, psoriasis, hives, allergies, vitiligo, or spots of excessive pigmentation (melanoderma). Insufficient levels of cortisol can also cause flu-like fatigue that gets worse under stress, cravings for sweets and/or salty and spicy foods, a dazed feeling and confused thoughts or empty-headedness, inability to handle stress, loss of appetite, nausea, digestive problems (including colitis), allergies and asthma, medication intolerance, rheumatoid arthritis, and regular spiking of fevers.