A molecular pathway could explain how a class of drugs leads to heart failure. Researchers who study how tumours balloon in size have discovered one way that enlargement of the heart can lead to heart failure. The work, although mostly done in mice, could help explain why a class of diabetes drugs called thiazolidinediones (TZDs) increase the risk of heart failure.These drugs have been controversial since a 2007 analysis1 of Avandia (rosiglitazone), a TZD made by GlaxoSmithKline, suggested that patients taking it are at increased risk of heart attack. Less controversial are data linking TZDs with heart failure, a distinct...