COMT and Parkinson disease: This hypothesis is consistent with [18F]DOPA-PET studies indicating a hyperdopaminergic state in prefrontal areas in early PD (79, 80) (presumably compensating for nigrostriatal dopamine loss), as well as a more recent [18F]-DOPA study indicating that COMT met alleles are associated with reduced dopamine metabolism and higher synaptic dopamine levels in frontal brain regions in early PD patients (81).