Using testosterone to categorise male and female athletes isn't perfect, but it's the best solution we have | Joanna Harper

An important new study could lead to the reinstatement of rules imposing a maximum level of male sex hormones in athletes competing as female

• Caster Semenya could be forced to undertake hormone therapy for future Olympics

While it has long been recognised that testosterone (T) level differences are the principle cause of the athletic advantage that men hold over women, there has been little published data indicating that T differences among women can result in significant advantage for those with higher T.

This lack of scientific data was one of the main reasons the CAS panel issued a temporary ruling in favour of Dutee Chand's team in the 2015 trial against the IAAF.