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Figure 12.  TSH-induced thyrotoxicosis in a 33-year-old woman. Laboratory values were as follows: free T4 = 2.0 ng/dL, T3 = 191 ng/dL, and TSH = 37.1 µIU/mL. The latter measurement was repeated, and the value was 39.0 µIU/mL. Anterior distant Tc-99m pertechnetate image shows relatively high target-to-background activity, similar to that seen in Graves disease. CT of the brain performed at an outside imaging center revealed a pituitary tumor. Upon removal of the tumor, the symptoms subsided and thyroid function returned to normal.