In the second study, "Spironolactone Treatment for Boys with Familial Isosexual Precocious Puberty", - the patients received another medication, spironolactone (Aldactone). The drug blocked the effects of testosterone, -but bone age advancement did not improve. Some patients began experiencing gynecomastia (an abnormal growth of the male breasts). Researchers believe these may be the effects of elevated levels of estrodiol (a form of the female hormone, estrogen).