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

• 這封信函重新分析了英格蘭青春期阻斷劑研究（2011–15 年）中 24 名青少年的個別骨骼掃描，他們是 2019 年一篇較早論文所描述的 31 人群組的一部分。
• 使用青春期阻斷劑 2 年期間，平均骨質密度明顯落後於相同年齡和性別的其他青少年，在髖部和脊椎上大約落後標準量表上的一個「級距」。
• 2 年後，約三分之一的患者髖部骨質密度低到被視為異常，這個水準在相同年齡和性別的青少年中只占 2.3%。
• 超過四分之一的人脊椎骨質密度異常偏低，四人屬於人口中最低的 0.13%（約每 750 人 1 人）。
• 考慮患者的身高並沒有消除分數極低的那一組。
• 英格蘭的研究最初排除骨質密度本來就異常偏低的兒童。2012 年這項規定被放寬，允許「在特殊情況下」治療，儘管日後有骨質脆弱的風險。
• Biggs 主張，骨折應被記錄為副作用，並批評減少骨骼掃描頻率或改變此群體正常範圍的提議。

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.