Chicago actor Jeremy Piven has unexpectedly left the cast of the Broadway revival of "Speed-the-Plow" because of a mercury count that his doctor said was the highest level he'd ever seen.

Piven, 43, wanted to continue but he was advised to stop. Dr. Carlon Colker, who had been treating Piven, said Piven was suffering from "extreme mercury toxicity" and that "a test revealed that Jeremy had ... six times a healthy amount of mercury in his system." Piven has long been a sushi eater, often twice a day, which may be the ultimate cause of the problem.

A major symptom of mercury poisoning is extreme fatigue. Piven was also experiencing neuro-muscular dysfunction, which resulted in his having trouble lifting his arms and legs.

Piven has won Emmy Awards for his role as foul-mouthed Hollywood agent Ari Gold in the HBO series Entourage. He had been performing to critical praise in "Speed-the-Plow" since October.