Shanlee M. Davis, MD, PhD, associate professor of pediatrics, [Section of Endocrinology, University of Colorado School of Medicine], is corresponding author of an original investigation published March 29 by JAMA Network Open that considers the prevalence of an additional X or Y chromosome among men who served in the U.S. military. Davis and her co- authors conducted a cross-sectional study of 595,612 men in the VA’s Million Veteran Program, finding that 1 in 370 men had a sex chromosome aneuploidy, but only 14.2% were clinically diagnosed by the time they were 60 years old. Men with an extra X or Y chromosome have increased risk of delayed development, learning disabilities, type 2 diabetes, and cardiovascular disorders.