Athletics South Africa (ASA) on Monday said it would lodge an appeal after Olympic champion Caster Semenya lost her case challenging new rules forcing female athletes to regulate their testosterone levels.

Semenya's case has provoked a furious debate across sport worldwide about gender and "hyperandrogenic" athletes, those with "differences of sexual development" (DSD).

The decision on May 1 by the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland, means female athletes with elevated testosterone will have to take suppressive treatment if they wish to compete as women in certain events.

"We'll file the appeal as soon as we possibly can," said Vuyo Mhaga, spokesperson for the South African sport and recreation ministry.

Mhaga said the appeal, to be lodged at the Switzerland Federal Tribunal, would be based on complaints over the judges' past record on similar cases, lack of clarity over how the ruling could be implemented and how the evidence was handled.

"It is not explained how the IAAF (the International Association of Athletics Federations) is going to administer those regulations," he said.

"We feel that the scientific information that has been brought has been actually completely ignored and we've got a belief that a different court will arrive at a different determination.

"Everything is being done through Athletics SA."

The IAAF argued that athletes such as two-time Olympic 800 metres champion Semenya had an unfair advantage over others.

Semenya, 28, won the 800m at the Doha Diamond League meeting on May 3 in her first race after the ruling, saying that "actions speak louder than words".

Asked if she intended to take hormone-suppressing treatment, the three-time world champion said: "No way.

"I don't know what will happen next. But no one should tell me what to do, if people want to stop me from doing something that's their problem, not mine."

The South African government, sports bodies and fans have reacted in fury over Semenya's case, which many in the country see as having racist undertones.

The World Medical Association has urged doctors not to enforce the controversial new rules, warning that attempts to do so would breach ethics codes.

The court itself said there was insufficient evidence to overturn the new regulations, but it "expressed some serious concerns as to the future practical application" of the rules.

The rules must remain a "living document", which are revised based on new information, the court added. 

The DSD rules - first adopted last year but suspended pending the legal battle - came into effect on May 8, applying to distances from 400m to a mile, and includes the heptathlon.