SLC6A3 and Parkinson disease: As the current clinical studies showed, reduced dopamine transporter uptake of the bilateral caudates was observed in hyposmic PD compared with the normosmic PD patients [29], although another study showed olfactory dysfunction in early PD is not correlated with dopamine uptake (as a measure for dopaminergic degeneration), but with dopamine turnover (as a marker for dopaminergic presynaptic compensatory processes) [30].