Olympic 1,500 metres champion Asli Cakir Alptekin is facing a lifetime ban after being charged with a second anti-doping offence.
Cakir, who was given a two-year ban in 2004 after a positive dope test at the world junior championships, competed at the London Olympics last summer under a dark cloud of suspicion.
And following abnormal blood values from her biological passport is now facing an automatic lifetime ban.
Another Turkish athlete, double European 100m hurdles champion Nevin Yanit, also faces a ban after multiple positive findings in both in-competition and out-of-competiton tests.
Both athletes have been charged with anti-doping rule violations by the The International Association of Athletics Federations (IAAF) and are provisionally suspended.
Their cases have been referred to the Turkish federation for adjudication.