Cape Town - South Africa's queen of the track Caster Semenya may be forced, once again, to lower her testosterone levels.
If she doesn't, she will not be allowed to compete in her specialist 800m and 1 500m events.
According to the Daily Mail website, the IAAF will on Thursday announce a new set of rules for athletes with hyperandrogenism.
The report says that, once the rule changes have come into effect, Semenya, 27, will be forced to take daily medication to lower her testosterone levels.
If she doesn't, she will be forced to compete in longer distances - or, effectively, quit the sport.
The new rule will apply to distances between 400m and a mile and it is expected to be fully operating by November this year.
The IAAF introduced a similar rule in 2011 after Semenya’s dominant victory at the 2009 IAAF World Championships, and it had a major impact on her pace.
Thursday's announcement will not come as a surprise after the IAAF council last month approved a proposal to limit natural testosterone levels in women athletes in the above-mentioned distances.
It will also sidestep the Court for Arbitration of Sport's (CAS) 2015 decision to suspend regulations on hyperandrogenism in women's athletics.
While that decision was a major win for Semenya, it is not likely to count for anything moving forward given that the CAS is not a regulatory authority for world athletics.
Semenya's dominance was on show for all to see at the recently-completed Commonwealth Games in Australia, where she cruised to gold in both the 800m and 1 500m.
She is also a double 800m Olympic gold medallist.
BIG news coming on Thurs from IAAF. They will rule that Caster Semenya must take testosterone-lowering tablets or switch to 5000m. The rule for testosterone levels will apply from 400m to a mile— Gary Lemke (@GaryLemke) April 25, 2018