Objective　Estradiol　(E2)　acts　to　modulate　the　ratio　of　two　dopamine　D2　receptor　isoforms　(D2L/D2S)　by　the　nuclear　estrogen　receptor　(ER)　and　to　reduce　dopamine＇s　inhibitory　action　on　PRL　secretion.　Here　we　demonstrate　the　correlation　between　the　expression　of　ER　mRNA　and　D2R　mRNA　isoforms　in　pituitary　neoplasms　cells.　Methods　Twenty-four　human　pituitary　adenomas　(14　prolactinomas　and　10　gonadotrope　tumors)　were　examined　for　the　expression　of　both　ER　mRNA　and　D2R　mRNA　by　means　of　semi-quantitative　RT-PCR　analysis.　Results　No　significant　difference　was　found　in　ER　beta　mRNA　expression　levels　between　prolactinomas　and　gonadotrope　tumors　(P　=　0.871),　but　there　was　a　significant　difference　in　the　expression　of　ER　alpha　mRNA　(P　=　0.003).　The　significant　difference　was　found　between　the　two　pituitary　adenomas　types　in　both　levels　of　D2S　and　D2L　mRNA　expression　(P　=　0.036　and　0.007　respectively).　Furthermore,　both　levels　of　expression　in　prolactinomas　were　significantly　higher　than　that　in　gonadotrope　tumors.　Additionally,　a　negative　correlation　between　D2S　and　ER　alpha　mRNA　expression　and　a　positive　correlation　between　D2L　and　ER　alpha　mRNA　expression　were　found　in　these　tumors.　Conclusion　This　study　for　the　first　time　shows　a　good　correlation　between　expression　of　ER　and　D2R　isoforms　in　prolactinomas　and　gonadotrope　tumors.　Reducing　the　amount　of　the　ER　alpha　in　neoplasm　cells　can　alter　the　ratio　of　D2L/D2S,　which　may　increase　the　drug　sensitivity　of　pituitary　adenomas.