Proposed regulations on testosterone levels in women’s athletics have been criticised by academics who say they are not backed by scientific evidence and risk opening a pandora’s box on genetic advantages in sport.

The International Association of Athletics Federations (IAAF) put forward new regulations which could require some female athletes to lower their testosterone level. However the introduction of these regulations is currently on ice while the courts decide on a legal challenge brought by the South African athlete Caster Semenya, a female 800 metre Olympic gold medallist. A ruling is expected within days.

Two academics argue that the IAAF regulations are based on the idea that testosterone levels are the prime indicator of biological sex and of how well an athlete will perform – something they say goes against medical and scientific evidence. The IAAF regulations stipulate that female athletes with circulating testosterone levels of 5nmol/L or higher, and whose bodies respond to such sex hormones, must lower their testosterone levels to compete in women’s track events from 400m to 1 mile.

Dr Sheree Bekker and Dr Cara Tannenbaum, writing in the BMJ, said there was no valid test for determining whether someone was insensitive to testosterone, and physical genital examinations required by the IAAF regulations were “an invasion of personal privacy”.

“Men usually have higher levels of testosterone in the blood than women, but not always, since hormone levels in the blood depend on a lot of different factors such as age, health conditions, other medications, menstrual cycle and stress,” said Bekker, an applied health scientist at the University of Bath.

“Based on these circumstances, there can be overlap between blood levels of testosterone in some men and women, and especially athletes,” she said, adding that many factors – including access to training and funding – all contribute to who becomes a winning athlete.

Bekker and Tannenbaum argued there were no clear lines in the sand about what a “male” or “female” level of testosterone was, pointing to one study in which 74 of 446 male athletes had testosterone levels below the “normal male” lower limit of 8.4 nmol/L while 32 of 234 female athletes had levels above the upper “normal female” limit of 2.7 nmol/L. Eleven female athletes had levels over 8 nmol/L.

“What we are seeing is the policing of women’s bodies, problematically framed as fairness or protecting other women,” said Bekker. “We don’t need to be protected from women just as men in sport aren’t protected from other men.”

Bekker said focusing on natural levels of testosterone in women raised further issues. “This is about natural testosterone levels. Are we going to go to a point where we are banning people who are tall from playing basketball or swimmers with long arms? Those are also natural advantages,” she said.

While Semenya’s challenge and the article by Bekker and Cara Tannenbaum are focused on the matter of women with differences in sex development – such as intersex athletes – the proposed IAAF regulations could also have implications for trans athletes.

Debate around trans athletes’ participation in women’s sport is a heated one: the athletes Kelly Holmes, Paula Radcliffe and Sharron Davies recently said they were going to write to the International Olympic Committee requesting more research into whether transgender athletes are at an advantage. Radcliffe previously said trans women being able to compete in women’s events made “a mockery of the definitions of male and female sports categories”.

In response to the article by Bekker and Tannenbaum, the IAAF said: “The 5 nmol/L limit used in the IAAF regulations is not ‘arbitrary’. Rather, it is based on a comprehensive survey of all reliable reported data, which established that female athletes with ovaries will usually have testosterone in the range 0.06 to 1.68 nmol/L, and will not get anywhere near 5 nmol/L; whereas athletes with the DSDs (differences in sexual development) covered by the IAAF regulations will have testosterone levels in the normal male range (7.7 to 29.4 nmol/L) or above.”

• A correction was made to this article on 21 March 2019. The article originally said the ruling in the Semenya legal challenge to IAAF regulations would have implications on transgender athletes. This has been changed to could.