In addition to showing no benefit for subclinical hypothyroidism, levothyroxine is associated with a host of unwanted side effects, note editorialists William K Silverstein, MD, of Sunnybrook Health Sciences Centre, Department of Medicine, University of Toronto, Ontario, Canada, and Deborah Grady, MD, of the Department of Medicine, University of California, San Francisco. Some studies have shown a link between long-term levothyroxine therapy and an increased risk of cardiovascular disease, cardiac dysrhythmias, osteoporosis, and fractures, they explain.