Summary

Bone density studies of puberty blockers (drugs that pause puberty) usually report averages. Sociologist Michael Biggs argued that averages hide the patients who matter most: those whose bone density falls into the abnormal range. He used individual data released with England's 2011–15 early puberty blocker study, covering 24 patients scanned after 2 years. On average, bone density fell well behind other teens of the same age and sex. About a third of patients had hip bone density low enough to count as low bone mass, found in only about 2 in 100 teens. More than a quarter had low spine density, and four were in the lowest 1 in 750. The study originally excluded children who already had low bone density, but this was relaxed in 2012. This is a short re-analysis of a small group with no data on broken bones, but it shows reassuring averages can hide worrying individual results.

Key findings

• 这封信函重新分析了英格兰青春期阻断剂研究（2011至2015年）中24名青少年的个人骨扫描，他们是2019年一篇早期论文所描述的31人组的一部分。
• 使用青春期阻断剂2年期间，平均骨密度明显落后于同龄同性别的其他青少年，在髋部和脊柱上大致落后标准量表上的一个“台阶”。
• 2年后，约三分之一的患者髋部骨密度低到足以算作异常，这一水平在同龄同性别青少年中只有2.3%。
• 超过四分之一的人脊柱骨密度异常偏低，四人处于人群最低的0.13%（约750人中1人）。
• 考虑患者的身高并没有消除得分极低的这一群体。
• 英格兰的研究最初排除了骨密度已经异常偏低的儿童。2012年，这一规定被放宽，允许在“特殊情况下”进行治疗，尽管日后有骨质脆弱的风险。
• Biggs认为，骨折应当作为副作用记录下来，并批评了减少骨扫描频率或改变该群体正常范围的提议。

Conclusion

Biggs concludes that after 2 years of GnRHa, up to a third of patients had abnormally low bone density (Z-score below −2, the lowest 2.3% for sex and age), with a few in the lowest 0.13%. This undermines Joseph et al.'s reassuring conclusions. He calls their recommendations to reduce DXA monitoring and to redefine reference ranges for this cohort 'surprisingly complacent'. He argues that, rather than altering a measure that gives inconvenient findings, practitioners of puberty suppression must record fractures as adverse events. Whether cases of repeated fractures are exceptional is unknown because clinicians have not collected the relevant data.