Associations of sex steroids with bone maturation, bone mineral density, bone geometry, and body composition: a cross-sectional study in healthy male adolescents.

BACKGROUND: Although both testosterone (T) and estradiol (E2) are considered essential in the regulation of the male skeleton, there are few data concerning the relative contribution of T and E2 on bone mineral density (BMD), bone geometry, and bone maturation in healthy boys.

OBJECTIVE: The objective of the study was to analyze the relationship between T and E2 and BMD, bone geometry, skeletal maturation, and body composition.

METHODS: This is a cross-sectional study in 199 healthy boys (aged 6-19 y). T and E2 were determined by liquid chromatography tandem mass spectrometry. Whole-body and lumbar areal bone mineral density (aBMD) and bone area, lean mass, and fat mass were determined by dual-energy X-ray absorptiometry. Trabecular (distal site) and cortical (proximal site) volumetric BMD (vBMD) and bone geometry were assessed at the nondominant forearm and leg using peripheral quantitative computed tomography. Skeletal age was determined by an X-ray of the left hand.

RESULTS: T was positively associated with lean mass (P < .001), lumbar and whole-body bone area (P < .001), trabecular and cortical area (P < .01), and periosteal circumference (P < .01) at the radius. E2 was positively associated with lumbar and whole-body aBMD (P < .001), trabecular vBMD at the radius and tibia (P < .01), and cortical thickness at the radius (P < .05). E2 was an independent negative predictor of the endosteal circumference (P < .01). Moreover, E2 was positively associated with bone age advancement (P < .001).

CONCLUSION: Circulating E2 is positively associated with bone maturation and aBMD and vBMD and negatively with endosteal circumference in healthy boys, whereas T is a determinant of lean mass and bone size. These findings underscore the important role of E2 in skeletal development in boys.