SST5 and D2R expression was highest in prolactinomas showing the highest response to pasireotide and cabergoline in vitro (median D2R IRS 1.0 vs 8.0 for < 50% vs. > 50% inhibition by cabergoline and median SST5 IRS 3.5 avs. This evidence concerns the gene DRD2 and prolactin-producing pituitary gland adenoma.