Estrogens are essential for male pubertal periosteal bone expansion.

[aromatase deficiency]

The skeletal response to estrogen therapy was studied in a 17 -yr -old boy with congenital aromatase deficiency . As expected , estrogen therapy (1 mg estradiol valeriate /d from age 17 until 20 yr ) normalized total and free testosterone and reduced the rate of bone remodeling . Dual-energy x-ray absorptiometry-assessed areal bone mineral density (BMD ) of the lumbar spine and femoral neck increased significantly (by 23 % and 14 %, respectively ), but peripheral quantitative computed tomography at the ultradistal radius revealed no gain of either trabecular or cortical volumetric BMD . The increase in areal BMD was thus driven by an increase in bone size . Indeed , longitudinal bone growth (height , +8 .5 %) and especially cross-sectional area of the radius (+46 %) and cortical thickness (+12 %), as measured by peripheral quantitative computed tomography , increased markedly during estrogen treatment . These findings demonstrate that androgens alone are insufficient , whereas estrogens are essential for the process of pubertal periosteal bone expansion typically associated with the male bone phenotype .