South Korean actress Lee Si Young has opened up about a serious health issue caused by her intense fitness regimen, revealing that her testosterone levels rose so high that her body "couldn't recognize itself as a female body," prompting year-long hospital treatment.

The Sweet Home actress made the revelation on a recent episode of Zzanbro, a YouTube talk show hosted by Shin Dong-yup.

Sitting with fellow actress Kim Dasom, Lee eagerly revealed how her determination to work out every day after her divorce resulted in a weird side effect.

"My testosterone, it got too high... I had to go to the hospital for a year," Lee said. Lee, a former amateur boxer and fitness enthusiast, gained attention for her muscular transformation in the Netflix hit Sweet Home.

However, she explained that the transformation came at a cost. "I had more than 30kg of muscles for the first time... [Body fat] was around 6% then," she said.

The actress explained that while her physique became widely praised, internally her body was under stress.

She lost her menstrual cycle, a condition she had previously experienced during her boxing days. In the past, she said regaining some weight was enough to restore her cycle, but this time it didn't work.

After undergoing medical tests, Lee was told that the elevated testosterone levels were disrupting her hormonal balance.

"I was told my body couldn't recognize itself as a female body because my testosterone levels had gone way too high," she said.

Lee admitted the experience left her shaken. "I became a bit scared of losing that much [weight and body fat] again," she noted, suggesting she now takes a more cautious approach to physical training.

Lee is currently starring in the ENA drama Salon de Holmes as Kong Miri. The show airs Mondays and Tuesdays at 10 p.m. KST.

Known for her athleticism and action roles, Lee made her acting debut in the early 2000s and has since become one of Korea's most physically dynamic performers.

Her revelation contributes to the growing conversation about the health consequences of extreme fitness in entertainment.