Kenyan Emmaculate Anyango, the world's second fastest woman over 10km, has been suspended for six years for doping, the Athletics Integrity Unit (AIU) announced.
The 24-year-old Anyango tested positive for prohibited testosterone and the banned blood-boosting hormone EPO in four tests in Kenya between February and June.
The AIU said in its ruling on Friday that it had decided to "increase the period of ineligibility" from the normal four years because of "aggravating circumstances". It said these included using "multiple Prohibited Substances" and using testosterone on "multiple occasions".
The AIU also chided Anyango for her failure to respond to the charges. The AIU statement said that after the deadline had passed, she sent e-mails "stating, inter alia, that she had nothing to say in the matter and that it was for the AIU 'to see what to do to me'."
Anyango, an African Under-20 3 000m silver medallist in 2019, had been tipped as one of the East African nation's rising stars.
She became the second Kenyan woman to run 10km in under 29 minutes, finishing runner-up in Valencia in January behind compatriot Agnes Jebet Ngetich who won with a world record 28:46. That time, recorded before the first failed test, still stands.
Anyango also defied a strong field that included former New York and London marathon champion Joyciline Jepkosgei to win the women's cross-country race at Sirikwa Classic, a World Athletics Tour Gold meeting in Kenya's northwest in February.
Kenya has invested massively in the wake of a doping scandal at the 2016 Rio Olympics, creating its revamped anti-doping agency that year. Some 78 athletes have been sanctioned in the last three years alone.
In June, Kenya's 10km road race men's record holder Rhonex Kipruto was banned for six years for doping and his world mark cancelled by the AIU.
However, there are fears the programme could be undermined after the Anti-Doping Agency of Kenya said last month that severe budget cuts had halted tests.