Hormonal determinants of bone turnover before and after attainment of peak bone mass.

INTRODUCTION: Bone turnover decreases from adolescence into adulthood, but does not reach a nadir until the fourth decade. Biochemical markers of bone turnover reflect different processes before and after peak bone mass, so hormonal influences on bone turnover may differ before and after peak bone mass. OBJECTIVES: To describe the changes in bone turnover and hormones relevant to bone metabolism from adolescence into adulthood, and to identify which hormones correlate with bone turnover before and after peak bone mass. DESIGN/PARTICIPANTS: Two measurements of bone turnover markers and hormones were obtained 5-9 years apart in 116 healthy males and females recruited from secondary schools and general practices. Correlations were examined cross-sectionally and longitudinally. RESULTS: Dehydroepiandrosterone sulphate (DHEAS) correlated negatively with bone turnover cross-sectionally and longitudinally (r-0.59 to -0.69) in males and females under the age of 25 years. IGF-1 correlated positively with aminoterminal propeptide of type I procollagen (PINP) cross-sectionally and longitudinally (r 0.35) in women over the age of 25 years. After correction for change in BMI, there were significant longitudinal correlations between DHEAS and bone turnover in women under 25 years (r-0.62, -0.66) and IGF-1 and PINP in women over 25 years (r 0.56). CONCLUSIONS: We have described changes in bone turnover and hormones from adolescence into adulthood. Dehydroepiandrosterone sulphate correlates with bone turnover before peak bone mass which may represent a direct effect on bone metabolism or the role of dehydroepiandrosterone sulphate as a substrate for conversion to other sex steroids. IGF-1 is correlated with aminoterminal propeptide of type I procollagen in women after peak bone mass, which may reflect an influence on cortical modelling.

Attainment of peak bone mass at the lumbar spine, femoral neck and radius in men and women: relative contributions of bone size and volumetric bone mineral density.

The age at which peak bone mineral content (peak BMC) is reached remains controversial and the mechanism underlying bone mass "consolidation" is still undefined. The aims of this study were to investigate; (1) the timing of peak BMC by studying bone size and volumetric BMD (vBMD) as separate entities and (2) to determine the relative contributions of bone size and vBMD to bone mass "consolidation". A total of 132 healthy Caucasian children (63 boys and 69 girls, ages 11-19 years) and 134 healthy Caucasian adults (66 men and 68 women, ages 20-50 years) were studied. BMC was measured by DXA at the AP and lateral lumbar spine (LS) femoral neck (FN) and ultradistal radius (UDR). vBMD and bone volume (size) were estimated. Bone mass "consolidation" was examined between age 16 years to the age peak bone values were attained. During growth, BMC and bone size increased steeply with age and approximately 80-90% of peak values were achieved by late adolescence. vBMD at the spine and UDR (in women) increased gradually, but vBMD at the FN and UDR in men remained almost constant. During "consolidation", bone size continued to increase with little change in vBMD. Peak vBMD at the lumbar spine was reached at 22 and 29 years in men and women, respectively, but earlier at the FN at 12 years. At the UDR peak vBMD was achieved at age 19 years in women, with little change in men. In conclusion, peak vBMD and bone size are almost fully attained during late adolescence. Although speculative, the lack of change in vBMD during consolidation implies that the continued increase in bone mass may primarily be due to increases in bone size rather than increases in either trabecular volume, cortical thickness or the degree of mineralisation of existing bone matrix (vBMD). Skeletal growth and maturation is heterogeneous, but crucial in understanding how the origins of osteoporosis may begin during childhood and young adulthood.