The NHS Gender Identity Development Service (GIDS), based at London’s Tavistock and Portman NHS Foundation Trust, is England’s only provider of NHS specialist treatment for young people with gender dysphoria.

In 2010 GIDS and University College London’s Institute of Child Health applied for ethical approval to conduct a cohort study offering puberty blockers to a “carefully selected group of adolescents” with gender dysphoria in early puberty.

But questions continue to emerge about the researchers’ conduct of this early intervention study.

We reported in July that potentially crucial information may have been missing from the study’s protocol and patient information sheets, casting doubt as to whether participants gave informed consent.1 Critics had said that the researchers had downplayed interim findings that might suggest increased suicidality. And the researchers had not submitted the annual progress reports required by the NHS Health Research Authority (HRA), which promotes patients’ interests in health research. Also, despite the full study findings remaining unpublished, the NHS changed its policy to allow GIDS to prescribe these drugs to children under 12 in established puberty.

Here we present new allegations that the researchers might have broken rules when seeking ethical approval. They might also have misinterpreted another study’s findings about potentially worrying effects of the drugs on changing bone density.