Effects of 17 beta-estradiol, progesterone and tamoxifen on in vitro proliferation of human pituitary adenomas: correlation with specific cellular receptors.

Six human pituitary adenoma cultures, characterized for estrogen and progesterone (Pg) receptors, were treated with 17 beta-estradiol (17 beta-E2), Pg and tamoxifen (TAM) at different concentrations, alone and in combination, for 2, 4 and 8 days. Cell proliferation data showed in most cases a stimulating effect of 17 beta-E2 and an inhibitory effect of Pg on cell growth, which appeared to be correlated with specific receptor expression, but independent of pituitary cell hormone content. A marked inhibitory effect of TAM on cell proliferation was present in all cases, but, on the contrary, was independent of estrogen receptor expression.