Summary: Physical exercise benefits bone structure and mineralization, especially in children. Immediately following high-impact exercise, PTH increased and returned to resting values within 24 h in both groups, while sclerostin increased in men but not in boys. The underlying mechanisms and implication of this age-related differential response are unclear.
Introduction: Circulating sclerostin, a negative regulator of bone, decreases during puberty and increases in adulthood. Parathyroid hormone (PTH) is inversely related to sclerostin. In mice, sclerostin decreases following 24 h of mechanical stimulation. Its response to exercise in humans and, especially in children, in whom high-impact physical exercise benefits bone structure and mineralization is unclear. The aim of this study was to investigate the acute response of sclerostin to a single exercise session of high mechanical loading and the corresponding changes in PTH in boys and men.
Methods: Twelve boys (10.2 ± 0.4 years old) and 17 young men (22.7 ± 0.8 years old) underwent a protocol of plyometric exercises (total 144 jumps). Blood samples were collected pre-, 5 min, 1 h, and 24 h post-exercise.
Results: Boys had significantly higher resting values of sclerostin compared with men (150 ± 37 vs. 111 ± 34 pg/ml, respectively, p = 0.006). Following exercise, sclerostin markedly increased in men but this response was attenuated in boys (at 5 min: 51 ± 38 vs. 14 ± 21%, respectively, p = 0.005). PTH levels were similar in boys and men at rest and throughout the 24-h study period, increasing significantly (p < 0.001) 5 min after exercise, decreasing after 60 min post-exercise and returning to resting values within 24 h.
Conclusion: Although the PTH response was similar in boys and men, the sclerostin response was greater in men. The combined increases in PTH and sclerostin immediately post-exercise appear contrary to the accepted osteogenic effect of exercise. The underlying mechanisms and full implication of the differential response between children and adults need to be further examined.
Keywords: Bone; Children; Exercise; Mechanical loading; Osteocyte; Sost.