SLC6A3 and Parkinson disease: In the ELLDOPA cohort, 49 levodopa-naive PD patients with fatigue had similar [123I]-β-CIT striatal dopamine transporter uptake as 82 PD patients without fatigue.14 Another study showed no difference in 18F-dopa uptake between 10 fatigued PD subjects and 10 nonfatigued PD subjects.2,61