The study is a clinical report on a male child who underwent pubertal suppression at a clinic in Brazil. The clinic administered puberty blockers for two years and four months between the age of 11 and 14. The clinicians took brain scans and intelligence tests at three stages and vocal measurements at four stages.
The child's cognitive function declined across a range of measures: comprehension index from 101 to 86, working memory index from 83 to 74, processing speed from 68 to 64, and global IQ from 80 to 70. The study found no significant changes in brain matter, and vocal measurements remained near the child range.
An IQ of 70 is borderline for intellectual disability. Blocking puberty appears to have limited the child's cognitive potential - an unsurprising resut in line with the current understanding of puberty as a period for critical brain maturation. Medical professionals treating children for gender dysphoria must inform parents of this risk to gain their informed consent.