These include:1) aromatic amino acid decarboxylase-deficient individuals suffer from hypoglycemia [53], 2) patients with Parkinson's disease receiving oral dopamine precursor L-DOPA display reduced insulin secretion during oral glucose tolerance testing [54]; and 3) there is an inverse correlation between circulating concentrations of C-peptide and DA [55]. The gene discussed is INS; the disease is Parkinson disease.