Chinese actor Jet Li has received treatment for an overactive thyroid. The martial arts star, 50, was first diagnosed with the condition in 2010 and has managed to keep it under control with medication, but during the taping of a Chinese talent show he is judging he revealed he is struggling to manage the symptoms. The action star says, "I have hyperthyroidism, sometimes I'd lose 15 kilograms, sometimes I'd gain 15 kilograms. I'm really fat right now. That's a fact. And I haven't had a chance to slim down, because the medication I am taking controls my heart rate, so I cannot exercise... I'll wait until the doctor says I can do simple exercises before slimming down." An overactive thyroid, also known as hyperthyroidism, is a condition of the thyroid gland and affects the sufferer's metabolism and heart rate. It is incurable but can be controlled with medication. The Lethal Weapon 4 star insists he is determined to tackle the condition head on but admits he sometimes fears he will be unable to continue working. He adds, "I have brilliant days when I am at my best... as well as days when I question whether I can still continue working. I can be in pain, but I cannot cry, and must face it head on."