Antonio Becerra Fernández
Specialist in Endocrinology and Gender Identity and honorary professor at the University of Alcalá
An important bias is that they include at least three months of treatment with blockers. This treatment time is not from Tanner stage II-III (around 12-13 years of age) and up to 16 years of age, where oestrogens or testosterone were added. Blockers have to be used from Tanner stage II, when children are between 11 and 12 years old. At that age, three months does not block puberty, it is already very advanced.
Another bias is that in the cohort the proportions of sex assigned at birth are opposite to the usual. There were always more trans girls than trans boys, about two thirds, and now it has changed: 31% are transitioning from boy to girl (assigned male at birth), and the other 69% are transitioning from girl to boy.