Since hyperprolactinemia generally appears after ~73% striatal D2R occupancy [19], and TRS patients often show lower prolactin levels in blood [20], it has been argued that antipsychotics exert an ineffective dopamine blockade in TRS, for instance due to suboptimal or variable D2R engagement, receptor anomalies, or pharmacokinetic differences. The gene discussed is DRD2; the disease is hyperprolactinemia.