SURPRISE, Ariz. — Kansas City Royals left-hander John Bale will undergo surgery on Tuesday to correct a thyroid problem.

"John Bale has a condition known as Graves' disease, better known as hyperthyroidism," Royals manager Trey Hillman said Saturday. "It means an overactive thyroid gland. ... There are two options. You can medicate it or have it surgically removed. John has chosen the surgery on Tuesday in Kansas City."

The Royals learned of Bale's possible thyroid problem after a spring training physical detected abnormalities. Bale returned to Kansas City for further examinations.

The 34-year-old, who began last season in the rotation, is hoping to resume workouts after two weeks, if all goes well.

Bale went on the disabled list in April with a sore shoulder, then broke his left hand while rehabbing. He did return until September, when he pitched 11 1-3 scoreless innings in 10 relief appearances. He is projected as a left-handed setup man this season for closer Joakim Soria.

Bale had a 3-6 record with a 4.46 ERA in the majors with Toronto, Baltimore, Cincinnati and Kansas City. He also pitched three years for Hiroshima in the Japanese League.