Both males and females synthesize testosterone and estrogen. In addition to the well-known effects of these sex steroids on sexual development in males and females, respectively, receptors for these hormones affect development of bone, brain, liver, heart and blood vessels. Therefore, there are differences in development of many diseases between men and women including the age when the diseases begin, their symptoms and response to treatment. As the science of genomics (study of genes) progresses, diagnosis and treatments will become tailored to men and women (sex-based medicine) and eventually individualized. For more information please see the Institute of Medicine report W.T. Wizemann and M.-L. Pardue (2001). Sex affects health. Exploring the Biological Contributions to Human Health: Does Sex Matter? Report of the Institute of Medicine. Washington, National Academy Press.