A 67-year-old Chinese man sought medical help in a Taipei hospital because of progressive muscular weakness. Aside from somewhat elevated blood pressure he had been in good health. Doctors could find no abnormality except for a very low level of potassium in the blood. The man revealed that he had been taking a Chinese herbal remedy for his enlarged prostate. It turned out the remedy contained licorice root. Licorice has a long history in Chinese herbal medicine as a general healing agent. While the accounts of miraculous cures are highly suspect, glycyrrhizic acid, the active principle in the licorice root certainly does have physiological effects. Licorice was one of the first drugs used in the treatment of Addison's disease by western physicians. This is an ailment of the adrenal glands which results in reduced production of cortisol, a hormone that helps regulate blood pressure and water retention. It turns out that glycyrrhizic acid interferes with an enzyme that normally breaks down excess cortisol in the kidney. If you are really interested, the enzyme in question is 11-betahydroxysteroid dehydrogenase type 2! In any case, inactivation of this enzyme leads to elevated cortisol levels which can cause hypertension. Furthermore, high cortisol causes retention of sodium and excretion of potassium. Sodium retention in turn leads to excess water retention in the body. Potassium deficiency causes muscle weakness. The remedy? Remove the licorice and treat the patient with potassium supplements. In two weeks the gentleman had lost 2 kg in weight due to the elimination of water retention and his potassium and blood pressure returned to normal. All signs of muscle weakness disappeared. Physicians and patients need to be aware of the fact that licorice root may be lurking in herbal therapies and can lead to problems. Incidentally, there is no evidence that licorice has any benefit in the treatment of benign prostate hypertrophy.