- Bone age (BA) >15 years Note: 99% of adult height is achieved at a BA of 15 years, thus estrogen replacement will not result in stunting of height potential after this age. Although we could have chosen to include girls with a BA >14 in this study, we are limiting this to girls with a BA of >15 years. This is because 2% of growth potential persists at a BA of 14 years, versus only 1% at a BA of 15 years (~0.6" of potential height (130)). Thus, to avoid potential stunting of growth potential with estrogen replacement, we have chosen to include girls with BA of > 15 years.