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

• Brevet genanalyserede individuelle knoglescanninger fra 24 teenagere i Englands studie af pubertetsblokkere (2011-15), en del af en gruppe på 31 beskrevet i en tidligere artikel fra 2019.
• Over 2 år på pubertetsblokkere sakkede den gennemsnitlige knogletæthed tydeligt bagud i forhold til andre teenagere af samme alder og køn, med cirka ét ‘trin’ på standardskalaen i hofte og rygsøjle.
• Efter 2 år havde cirka en ud af tre patienter så lav knogletæthed i hoften, at den regnedes som unormal, et niveau, der kun findes hos 2,3 % af teenagere af samme alder og køn.
• Mere end en fjerdedel havde unormalt lav knogletæthed i rygsøjlen, og fire lå i den laveste 0,13 % af befolkningen (omkring 1 ud af 750).
• Hensyntagen til patienternes højde fjernede ikke gruppen med meget lave scorer.
• Englands studie udelukkede oprindeligt børn, hvis knogletæthed allerede var unormalt lav. I 2012 blev dette lempet for at tillade behandling ‘under ekstraordinære omstændigheder’, trods risikoen for skøre knogler senere i livet.
• Biggs argumenterer for, at knoglebrud bør registreres som bivirkninger, og kritiserer forslag om at scanne knogler sjældnere eller ændre normalområderne for denne gruppe.

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.