Despite findings from studies in animals that suggest testosterone encourages the buildup of plaque in the arteries, clinical studies in humans have suggested that the male hormone may instead protect elderly men from developing atherosclerosis. Findings from the University of Turku, Finland, confirm that in healthy middle-aged men, normal testosterone levels are protective against atherosclerosis. The study involved 99 men (average age 58) whose testosterone levels had declined, and compared them with 140 similar men who had normal levels. After taking into account age, blood pressure, and other determining factors, researchers found that artery wall thickness increased as levels of testosterone decreased. They found that the thickness of the wall of the carotid artery was significantly higher in men with lower testosterone levels. The researchers agree that further studies are needed to investiagte the effects of testosterone supplementation on those whose levels decline with age.