It has been known that both estrogen and testosterone are the major sex steroids regulating bone metabolism and other physiological changes in both male and female, respectively. In postmenopausal women, osteoporosis is a major concern secondary to the lack of estrogen. These patients also experience a number of physiological changes that affect their life permanently to include hot flashes, irritability, difficulty concentrating, depression and mental confusion. In hypogonadal men, testosterone deficiency could lead to higher prevalence of depression, osteoporosis, fracture and frailty. Given the new military policy starting to support treatment for gender identity dysphoria military personnel, the number of transgender patients in our Endocrinology clinic has been slowly increasing over the past several months. These patients will require either testosterone replacement therapy or estrogen therapy to achieve their desired sexual characteristics. However, as mentioned above, the lack of estrogen or testosterone in female and male, respectively, could cause several issue in their body composition, cognitive function and quality of life. We designed this prospective case-control study to include patients with hypogonadism and the transgendered populations to learn about the long-term effects of these hormonal replacement therapies on bone density, fractures, memory/cognitive function and quality of life. This is a repetitive measures study taken at baseline, 6-months, and 12-months for three groups consisting of at least 75 subjects. The study will involve 3 arms, i.e. Group 1 primary/secondary untreated hypogonadism, Group 2 male-to female (MTF), and Group 3 female-to-male (FTM) participants that are planning to start hormone replacement therapy as per standard clinical guidelines.