Five world experts will be called upon to support the IAAF's bid to introduce a hyperandrogenism rule, one which is being challenged by two-time Olympic champion Caster Semenya.

In April, athletics' governing body announced planned protocols affecting women with higher than normal levels of testosterone who compete in track events ranging from the 400 metres up to a mile.

The IAAF stated in June those distances were selected because the "performance advantage" of having higher levels of circulating testosterone are "most clearly seen".

Under the regulations, some female athletes would have to reduce their blood testosterone levels to below five nmol/L for a continuous period of at least six months and then maintain it beneath that level – whether in or out of competition – for so long as they wish to remain eligible.

South African Semenya, winner of the 800m at each of the last two Olympic Games, lodged an appeal against the rules with the Court of Arbitration for Sport - a move that received backing from her government ahead of the start of the case being heard on Monday.

And on Monday, the IAAF issued a release announcing it would call on five experts - including from the fields of obstetrics and gynecology, pharmacology, andrology and law - to support its argument.