Effect of tamoxifen administration on prolactin release by invasive prolactin-secreting pituitary adenomas.
Bromocriptine treatment of patients with invasive prolactin (PRL)-secreting pituitary adenomas does not invariably result in normalization of the plasma PRL levels. We previously showed that the antiestrogenic drug tamoxifen inhibited hormone release from transplantable PRL-secreting pituitary tumors in rats. In 8 patients with invasive PRL-secreting pituitary adenomas with extrasellar extension, the effect of the administration of tamoxifen was investigated on the plasma PRL concentration and on the bromocriptine-mediated inhibition of PRL release. Treatment for 5 days with tamoxifen (20 mg/day) suppressed plasma PRL levels as measured in 5 samples over the day significantly by 20 +/- 3% (means +/- SEM; p less than 0.01). During tamoxifen administration the inhibition of PRL secretion by 2.5 mg bromocriptine was further suppressed by 36 +/- 7%, in comparison with the plasma PRL levels after bromocriptine alone (p less than 0.01). Tamoxifen administration suppressed PRL release in patients with giant invasive PRL-secreting pituitary adenomas, and it had a slight but significant additive or potentiating effect on the bromocriptine-mediated inhibition of PRL secretion. However, despite the simultaneous administration of bromocriptine and tamoxifen, normalization of the circulating PRL levels was not reached in this type of patient.
D000236:Adenoma / Q000188:drug therapy*; D000328:Adult; D001971:Bromocriptine / Q000627:therapeutic use; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000188:drug therapy*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D013629:Tamoxifen / Q000627:therapeutic use*
D013629:Tamoxifen; D001971:Bromocriptine; D011388:Prolactin