Description: Hip fracture, a very disabling and costly condition to individuals and society, is typically thought of as a health problem of older women. However, 25-30 percent of hip fractures occur in men, and by 2025, the incidence of hip fracture in men is expected to be the same as that currently seen in women, making this an emerging public health concern for older men, their families, and the healthcare system. Abstract: Most of what is known about the consequences of hip fracture comes from studies of women. In 2005, the National Institute on Aging awarded Dr. Magaziner a Merit Award (R37 AG09901) to extend this body of work on the consequences of hip fracture to include an investigation of functional, metabolic, physiologic, muscular and skeletal consequences of hip fracture in men in comparison with women. The proposed ancillary study is designed to extend this investigation of the hip fracture consequences further by examining trajectories of change in bone strength, bone metabolism, muscle composition, hormones, and markers of inflammation following hip fracture, and by comparing these changes in men and women during the year following a hip fracture. Ascertaining this information is important since without knowing how men and women differ, it is not possible to decide which information already known about women who have hip fractures can be applied confidently to men. In Component 1 of this study, men and women who are being recruited with a new hip fracture for the parent study will be compared on measures of bone strength and turnover, muscle composition, hormones and inflammatory markers. Where measures or specimens for the ancillary study can be obtained directly from information collected as part of the parent study, 200 men will be compared to 200 women. When new measures of bone strength and muscle composition are required, additional measures will be made on a subset of male and female patients. In Component 2 of this study, emphasis will turn to identifying changes in selected aspects of bone, muscle, function, and metabolism attributable to hip fracture in men. This aim will be accomplished by comparing the 200 men in the Component 1 cohort with 200 men matched on age and race/ethnicity from the Male Osteoporosis Study (MOST). Sample sizes for both components are large enough do detect small to moderate sized differences in longitudinal analyses. Together with information being collected in the parent project, new information from the ancillary study will allow us to determine where the next set of etiologic, prognostic, and mechanistic studies should be targeted, and areas in which interventions need to be developed and tested to improve the outcomes of hip fracture in men and in women.