GCG and type 2 diabetes mellitus: Exenatide has been shown to increase transcription of tyrosine hydroxylase (the rate limiting enzyme in dopamine synthesis) in brainstem catecholaminergic neurons.10 Furthermore, stimulation of GLP-1 receptors may have beneficial effects on the neurodegenerative processes of PD through downstream cellular pathways.6 11 These findings are further supported by a recent study suggesting a reduced future risk of developing PD in T2DM patients treated with GLP-1 agents.12