- Females 14-21 years old Note: Our pilot data are reassuring in that young women 18-25 years old with hypothalamic amenorrhea are not adversely affected with estrogen use. In fact, in our prospective study, beneficial effects were observed both in young women 18-25 years old using oral estrogen, and in 14-18 year old adolescent girls using transdermal estrogen. We therefore feel that including girls in the 14-21 year age range will not be hazardous to their bone health. In fact, given the lack of data in this age group, it is important to study younger women and teenagers rather than extrapolate data from studies in adults to this younger population. Hormone dynamics differ in teenagers compared with adults, and bone mass accrual is even more dependent on estrogen and IGF-1 in younger than older women who have already achieved peak bone mass.