Doctors will be told to show caution in prescribing puberty blockers in New Zealand after a review found strong evidence for their effectiveness and safety was lacking.

The Ministry of Health today released its long-awaited evidence brief and a position statement on puberty-stalling hormones.

“The evidence brief found that the evidence supporting the effectiveness and safety was limited and of poor quality,” the ministry said.

As a result of the findings, the ministry is outlining an expectation that greater caution is used in prescribing the medication. Further safeguards may be introduced after consultation with interested parties.

Other countries have also taken steps to restrict puberty blockers out of concern about a lack of robust evidence and rising prescribing rates.

New Zealand has not gone as far as the United Kingdom, which has banned their routine use. The ministry’s approach was applauded by experts in this country, who said a ban would have gone too far and would have removed a medication that has improved the mental health of some individuals.

Puberty blockers can be prescribed to stall unwanted physical changes in young people with gender dysphoria - the psychological distress that arises from the feeling of being born in the wrong body or assigned the wrong gender. Advocates say this can provide time to explore gender identity and potentially improve mental wellbeing.

Prescribing rates have been gradually rising in New Zealand. In 2010, around 25 people aged between 11 and 17 were started on the treatment, the ministry said. That rose to 140 in 2021, before falling to 113 last year.

The ministry reviewed 4000 international studies for its evidence brief. Among the key findings was that patients who had taken puberty blockers had lower bone density than expected when compared to other young people at the same stage of development.

Another key finding was that there was no evidence that the medication, known as GnRH analogues, had any significant effect on renal or liver function or fertility.

At present, puberty blockers can be prescribed by clinicians in New Zealand as part of gender-affirming care when a patient reaches puberty.

As of today, the ministry is now outlining a more cautious approach to prescribing the medication.

“The ministry’s assessment is that the starting point for treatment is a holistic assessment determining the full spectrum of needs a young person may have including social and mental health.

“The new precautionary approach signals the need for clinicians to exercise caution in prescribing, including that prescribing should only be initiated by clinicians who are experienced in providing gender-affirming care, and are part of an interprofessional team offering a full range of supports to young people presenting with gender identity issues.”

The ministry will consult on whether further regulations are needed, such as amendments to the Medicines Act to formalise changes in prescribing expectations.

“These tighter controls reflect a level of concern here and overseas about the increasing use of these medicines for the treatment of gender identity issues without sufficient evidence to support their safety and effectiveness both now and in the longer-term,” the ministry said.

Professor Paul Hofman, a paediatric endocrinologist at the University of Auckland, said the ministry had taken a “very reasonable” approach.

“Encouragingly, the evidence published to date, while of low quality, all indicates the use of pubertal blockers is safe,” he said.

“The effectiveness of treatment varies depending on the study and this may reflect a number of variables including the appropriate selection of patients for pubertal blockade.

“At an individual level there are clear reports of improvement and it would be inappropriate to withdraw the use of this medication for the (likely many) patients suffering from gender dysphoria where it could improve mental health.”

Dr Massimo Giola, a sexual health physician, also said the ministry had taken a reasonable position.

“In my opinion gender care should always be delivered in a multidisciplinary context, combining relevant medical and mental health professional profiles ... and obviously caution should be exercised in prescribing, as in any other case.

“I think it is a well-balanced position and does not affect the way gender care is and should be delivered.”

Other steps are also being taken by the ministry and Health NZ - Te Whatu Ora, including updated clinical guidelines on puberty blockers, better monitoring of use in New Zealand and developing New Zealand’s local knowledge on the subject to guide further advice. Research is also being commissioned on the long-term clinical and mental health affects of puberty blockers.

The Act Party welcomed the ministry’s change of approach, saying it brought New Zealand into line with other countries.

Isaac Davison is an Auckland-based reporter who covers health issues. He joined the Herald in 2008 and has previously covered the environment, politics and social issues.