Severe drug-related hyperprolactinemia (commonly defined as PRL values above 100 ng/mL), in the context of 100–250 ng/mL (approximately 2120–5300 mIU/L) and > 250 ng/mL (> ~5300 mIU/L), were found to occur in ~30% and ~5% of the cases (particularly with antipsychotics), respectively (50, 51). This evidence concerns the gene PRL and hyperprolactinemia.