Effect of graded oral doses of oestradiol on circulating hormonal levels
Dada, O.A.; Laumas, V.; Landgren, B.M.; Cekan, S.Z.; Diczfalusy, E.
Acta Endocrinologica 88(4): 754-767
1978
ISSN/ISBN: 0001-5598 PMID: 581116 Document Number: 127399
A single oral dose of micronized estradiol (1, 2 or 4 mg) was administered to 10 normally menstruating women on the 2nd day of 3 consecutive menstrual cycles. The order in which the 3 doses were given was chosen randomly for each subject. Samples of peripheral blood were withdrawn on 3 occasions (10, 5 and 1 min) before and on 9 occasions (0.37, 0.75, 1.5, 3.0, 6.0, 12.0, 24.0, 48.0 and 72.0 h) after estradiol ingestion. Estradiol, estrone, estradiol sulfate estrone sulfate testosterone and LH were measured by means of radioimmunoassays in blood plasma on all occasions. The levels of all estrogens increased significantly following the ingestion of estradiol, although to a greatly different extent. The largest and most prolonged increase was seen in the case of estrone sulfate, the levels of which, depending on the dose ingested, were 20-50 times higher than the pre-treatment levels 3 h after the ingestion of the estradiol capsule. The increase of the levels of estrone sulfate was still significant (P < 0.001) after 24 h, and following the ingestion of 2 and 4 mg of estradiol even after 72 h (P < 0.05). The levels of estrone and estradiol sulfate exhibited smaller increases 3 h after ingestion, i.e., 4-10 and 2.5-5 times, respectively, and the plasma estradiol levels showed a minor increase only (1.4-1.8 times). The concentration of estradiol metabolites studied increased proportionally with the dose of estradiol administered. A clear-cut dose-effect relationship could not be observed between the amount of estradiol administered and the plasma levels of LH and testosterone. Apparently the bulk of perorally administered estradiol is transformed to estrone sulfate accompanied by smaller quantities of estrone and estradiol sulfate and that the ratios of circulating estrogens seen after estradiol ingestion deviate considerably from those observed in the normal menstrual cycle.