The adrenal glands sit atop the kidneys and secrete a variety of hormones including adrenaline, male sex hormones, and cortisol, a hormone produced in response to stress. Two well-known adrenal gland disorders are Cushing's Syndrome, marked by excessive hormonal production and Addison's disease, marked by adrenal deficiency.
"Adrenal exhaustion" and "adrenal fatigue" are popular diagnoses among alternative medicine practitioners but are not recognized in conventional medicine. They are often made by people not qualified by medical training (including nutritionists, chiropractors, massage therapists and health food store clerks) and are unlikely to be valid. Symptoms of adrenal exhaustion are usually vague and non-specific - fatigue, lack of energy, depression, weight problems, and insomnia. It is conceivable that very severe stress (resulting from a prolonged illness, for example) could lead to an adrenal imbalance, but I'm not sure that there is any physiological basis for the notion that everyday stress can ever "exhaust" the adrenals. Some treatments recommended for this questionable condition usually are innocuous - rest, stress reduction, a healthy diet, and vitamin/mineral supplements. Others are not, especially adrenal glandular products. I strongly advise against taking any supplements that contain adrenal glandular tissue. (In fact, never take any over-the-counter glandular supplements.) At best, they are unnecessary; at worst, dangerous. They can disrupt the body's hormonal balance, which is maintained by a delicate and interconnected set of controls.
If you feel that you're under stress and need a lift, I recommend taking a multivitamin with B-complex vitamins, as well as cordyceps and tonic herbs such as American ginseng or Eleuthero ginseng. In addition, try relaxation techniques such as deep breathing, meditation, yoga or biofeedback to help reduce the stress itself.
Andrew Weil, M.D.