"It represents a rapid change in the population's understanding of the range of gender identity in individuals and the practicality of therapy," study author Dr John Delahunt, of Otago University's Department of Medicine, said of the findings.
"However, we could only note the rate of change of referrals not the reasons for this."
Still, Delahunt and his co-authors noted it seemed "likely to be related to the increasing societal awareness and acceptance of gender diversity".
Many people had also found out more information through the internet, or had linked with other transgender people in online groups.
The authors wrote there was also "an increasing awareness" that a change of gender appearance was a practical option with hormone therapy.
In the past, endocrinologists in Wellington had been prepared to accept referrals for the consideration of hormone therapy in adults without prior assessment from a mental health professional, largely because resourcing limited access to such checks within the public health system.
The authors noted that referral pathway had since been adjusted, and now included a comprehensive psychosocial assessment conducted within the unit, before hormone therapy was initiated.
Another factor could have been support available in the region: special practices that offered counselling, support and group discussion for teenagers had only been in place since 2004.
Delahunt said the "Youth 12" survey conducted in Auckland in 2012 indicated 1.2 per cent of teens identified as transgender.
"We do not expect 1.2 per cent of teenagers would seek advice on transgender management, but this number does represent a potentially large pool of individuals who may want to work through gender-related issues."
He said the study was mainly aimed at clinicians and health administrators to "highlight an area of increasing need" - and one that would require medical professionals to work together.
'I was going in the right direction'
For one Wellingtonian, who asked only to be named as Ash, gender reassignment surgery was a journey that began with worry and doubt.
But, the closer 32-year-old moved toward the decision, the better it felt.
"I started transitioning from around 25 and decided to go through surgery at 31," Ash said.
"Each step of my transition affirmed that I was going in the right direction.
"I decided to follow through with surgery when it got to the point where the uncomfortableness I was experiencing in intimate situations was interfering with my relationships."
Years of research, counselling and therapy, and all the science also pointed to a ''yes'' decision.
"Through the internet, I could connect with people across the world who felt the same way, and I realised it is actually not uncommon - I believe one per cent of any population are in some way gender diverse."
Moving from provincial New Zealand to Wellington - "a beautiful and welcoming and accepting place" - also played a big part.
"In Wellington, I found some amazing communities of supportive people and that's why I stayed here.
"I also found someone who had seen my surgeon and she was very happy to share her experience and advice with me, and that was an amazing gift."
Ash opted to undergo in the surgery in Thailand, and saved for years to afford the $25,000 cost.
"I knew that if I was going to have to wait for the New Zealand health system that I would have to jump through dozens of hoops, maybe see someone in 5 to 10 years at best, and get a low-quality result.
"I believe New Zealand should be funding trans people to see surgeons overseas."
While the world wasn't perfect in other ways - it remained hard to be non-binary, even today, and Ash described the current US administration as "appalling and terrifying" - attitudes and acceptance had "improved dramatically" in the past decade.
"Not just from LGBTIQ+ people, but also straight, cisgender people, who believe us and support us - some of them are my best friends."
