How much testosterone is too much for a female athlete?

South Africa's Caster Semenya celebrates after winning the gold in the women's 800-meter final during the Diamond League in Doha, Qatar, Friday, May 3, 2019. [Agencies]

The South African athlete, Caster Semenya, has lost her case against the athletic governing body, IAAF, which means that she will have to take medication to lower her testosterone levels if she wishes to continue competing internationally in running events.

Last year, the IAAF introduced new regulation for female athletes with “difference of sexual development” (DSD). Athletes with circulating testosterone of five nanomoles per litre of blood (5nmol/L) or above and who are androgen-sensitive, have to meet certain criteria if they wish to compete internationally. One criterion is that DSD athlete must use medication to reduce their blood testosterone level to below 5nmol/L for a continuous period of at least six months.