Indian sprinter Dutee Chand has started an appeal at the Court of Arbitration for Sport (Cas) against her indefinite ban from competition.
Chand, 19, has not been allowed to compete since last summer after failing a hormone test.
The test revealed her body produced natural levels of testosterone above International Association of Athletics Federations (IAAF) guidelines.
Her legal team will argue the ruling is discriminatory and flawed.
There is currently no similar assessment for male athletes.
|READ MORE: What is the hormone test? Dutee Chand's story and a history of controversy|
The landmark case against the IAAF and Athletics Federation of India started on Monday at Cas in Lausanne, Switzerland, and is expected to last up to four days.
A final judgement could take weeks or even months.
Chand was forced to miss the Commonwealth Games and Asia Games after failing the controversial test but refused medical treatment to help make her eligible.
Her appeal is the first to challenge the "hyperandrogenism" rules the IAAF introduced in the wake of the Caster Semenya affair in 2009.
|Born on 3 February, 1996, the third of seven children to a weaver couple from the state of Odisha|
|Becomes Indian national under-18 champion for 100m when she clocks 11.8 seconds in 2012|
|Wins a 200m bronze at 2013 Asian Games and is first Indian to reach a global sprint final at the World Youth Games, coming sixth in 11.62 seconds|
|Claims 100m/200m double at Asian Junior Athletics Championships, prompting the Athletics Federation of India to ask for a hormone test in July|
Subjected to enormous media scrutiny, Semenya subsequently returned to the sport, winning an Olympic silver medal at London 2012.