Transgender female athletes must lower their testosterone levels by half under new regulations introduced by the International Association of Athletics Federations (IAAF).

The IAAF Council, which met in Doha, approved eligibility rules that require the concentration of testosterone in an athlete to be less than five nanomoles per litre continuously for a period of at least 12 months prior to being declared eligible. The previous limit was 10 nanomoles.

Caster Semenya. Credit:AP

The athlete must also keep the levels below that mark to maintain their eligibility to compete in the female category.

The change brings the regulation into line with that which applies to athletes with differences of sexual development, like Caster Semenya who is currently challenging the rules.

"Under the new regulations a transgender female athlete is no longer required to be recognised by law in her new gender but should provide a signed declaration that her gender identity is female," an IAAF statement said.

"She must demonstrate to the satisfaction of the expert panel that the concentration of testosterone in her serum has been less than 5nmol/L continuously for a period of at least 12 months prior to being declared eligible, and must keep her serum testosterone concentration below that level to maintain her eligibility to compete in the female category."

PA