In conference today Dr. Kirmani presented his data on the topic of increased fractures in puberty. He noted that in reviewing data gathered over the last 4-5 decades by the Mayo Clinic, there is an increase in fractures during puberty in both boys and girls. Overall, the frequency of fractures is also increasing over this time period.
In order to study this, the group looked at the distal radius (the most common site of fractures in this age group). They used a novel technique of high-res QCT to obtain images that were very close in detail to bone biopsy. By enrolling subjects in different age groups, they were able to gather data regarding the changes that take place in terms of bone.
As seen in the figure, the cortical portion of the bone becomes the weakest during puberty as bone growth occurs. This may be due a delay in the formation of cortical bone as opposed to trabecular bone as overall lengthening occurs. The reasons behind this are unknown but many in the audience suggested a local action of PTH in serving up cortical bone as a source of calcium (similar to that seen in breast feeding).
Regardless of the etiology, due to the lenghtening process without adequate thickening, the bone strength is approximately 1/8 that of the original bone thus leading to increase fractures.