Bone Abstracts

Background: Although both testosterone and estrogens are considered essential for normal bone growth, epiphyseal maturation and bone mass accrual during adolescence, only very few data concerning the changes of estrogens, bone maturation, bone mineral density (BMD) and bone geometry in healthy boys at different pubertal stages have been published.

Objectives: This study aimed to analyze the relationship between sex steroids and more especially estrogens and skeletal maturation, BMD and bone geometry in healthy boys and adolescents.

Methods: Two hundred and five healthy boys (aged 6–18 years; median age 13 years) were included in this cross-sectional study. Pubertal status of the subjects was assessed according to the method established by Tanner. Estradiol (E₂) and testosterone (T) levels were determined by liquid chromatography tandem mass spectrometry. Whole body areal bone mineral density (aBMD) and area, lumbar aBMD and area were determined by DXA. Trabecular (4%) and cortical (66%) volumetric BMD and bone geometry (trabecular area, cortical area, periosteal circumference, endosteal circumference and cortical thickness) were assessed at the non-dominant forearm using pQCT. Skeletal age was determined by an X-ray of the left hand and wrist.

Results: As expected increasing sex steroids (E₂ and T) levels were found with advancing pubertal development (P<0.001). Lumbar and whole body aBMD and area, trabecular and cortical vBMD, trabecular and cortical area, periosteal and endosteal circumference and cortical thickness increased significantly throughout puberty (P<0.001). Regression models including age and BMI showed that estradiol (E₂) was positively associated with lumbar (E₂: β: 0.35 P<0.001) and whole body aBMD (E₂: β: 0.20 P<0.001), trabecular vBMD (E₂: β: 0.32 P<0.01), and cortical thickness (E₂: β: 0.27 P<0.01) at the radius. Moreover, E₂ was positively associated with the degree of bone age advancement (E₂: β: 0.26 P<0.01). No associations were found between E₂ and cortical vBMD and endosteal circumference. Testosterone was positively associated with lumbar (T: β: 0.36 P<0.001) and whole body area (T: β: 0.23 P<0.001), trabecular (T: β:0.29 P<0.01) and cortical area (T: β:0.21 P<0.02), periosteal circumference (T: β: 0.28 P<0.001).

Conclusion: Circulating estradiol is strongly associated with bone maturation and areal and volumetric bone mineral density in healthy boys, whereas testosterone determines mainly bone area (lumbar spine area, whole body area, cortical area and trabecular area, periosteal circumference). These cross-sectional findings need confirmation by a longitudinal study.