Otago University used to prop up puberty blocker claims

Adolescents acquire adult levels of bone mass during puberty. Blocking puberty is known to impact bone health in the short-term and has potential long-term impacts as well.

Bone health impacts must weigh on the minds of clinicians who prescribe puberty blockers. On March 1st TVNZ published an article where Auckland-based opposite-sex imitation clinician and PATHA executive committee member Dr Rachel Johnson had the following to say:

“We know that bones, while someone is on a blocker, they’re just not building up in the same way they usually would do in adolescence. We still don’t know when you’re 60 or 70, whether that might have an impact…”

The same day, two Otago University academics, Dr (Dame) Sue Bagshaw and Dr Jane Spittlehouse released a statement (the “Otago statement”) regarding a student’s literature review conducted over the previous summer.

Bagshaw is also the medical director of the 298 Youth Health Centre in Christchurch. 298 Youth Health has around 100 trans or non-binary identified youth under their care, and about 65 of them are on puberty blockers. Dr Bagshaw has been prescribing puberty blockers “for 20 years” (Chisholm, 2021).

The literature review concerned the impacts and benefits of puberty blockers for treating adolescents with gender dysphoria. The review has not been published, but the media statement made claims about the review’s findings, including claims on the impacts of puberty blockers on bone health:

“One exception is that use of puberty blockers does result in a decrease in bone mineral density, but this normalises when GnRH analogues are stopped and either a return to self-produced or cross-sex hormones are started.”

The claims were repeated in several media articles. Johnson must have found the Otago statement reassuring. In a Listener article published June 26th, Johnson had changed her position on the long-term bone health impacts of blockers:

“Research is showing that when you either stop the blocker or add in gender-affirming hormones then the bone density improves. Bone density is restored within approximately three years.”

The only “research” that makes claims resembling the above is the Otago statement. The literature review’s lack of publication and peer review did not stop Johnson from paraphrasing it. Presumably, both Bagshaw and Johnson now inform their patients that their long-term bone health is not at risk from blockers.

Unfortunately, the claims are false. No research that demonstrates that bone density is “restored within three years” under estrogen or self-produced hormones. There is some evidence of bone density recovery under testosterone, but that is not what Bagshaw, Spittlehouse, and now Johnson have claimed. The evidence for bone health impacts is reviewed in the bone health section.

It is not clear how Bagshaw and Spittlehouse justify the claims. We have made an OIA request to Otago University to bring light to the matter and will update this blog with further information. The troubling, and frankly, bizarre quirk to this story is a second summary of the literature review that contradicts a claim made in the Otago Statement. The second summary is published on The Collaborative Trust website, an NGO associated with Dr Bagshaw. In the Collaborative Trust summary, the claim that bone density will normalise under self-produced hormones does not appear. Instead, the summary notes (correctly) that there is no evidence for recovery in the self-produced hormones case:

“There is a lack of evidence around the impacts of bone mineral density for those who do not receive new sex hormones.”

Perhaps the two literature review summaries were written by different people who disagree on the literature review’s findings? It is hard to know when the review does not exist publicly. In any case, the claim that bone density recovers from puberty blockers under all circumstances has gone halfway round the world, while the truth is still getting its shoes on.

Conflicts of Interest

Clinicians who have been prescribing blockers “for 20 years” will struggle to give an unbiased account of the research. Imagine the consequences of discovering that you had been misinforming patients and had to have a series of difficult conversations. Conversations that might lead to complaints of professional misconduct. Fallible clinicians would be inclined to downplay the research that suggests a favoured treatment could cause harm and highlight research that suggests benefits. Well-regarded evidence-based guideline development institutions such as NICE (UK) and Cochrane (International) limit the number of clinical practitioners on guideline development committees for this reason.

New Zealand does not have the independent clinical guideline development institutions of the UK. Instead, we rely heavily on expert judgement. The COVID pandemic has heightened concerns about medical misinformation. In response, the media has taken a more active role in distributing the official medical advice from trusted experts and shifted away from a “both sides” debate-style presentation of medical issues.

That’s understandable during a pandemic. But not every medical issue will have its ‘trusted experts supported by a solid scientific consensus’. Medical controversies still exist, and Bagshaw and Johnson have been found wanting.


otago university