Profiles of plasma estrogens, progesterone and their metabolites after oral or vaginal administration of estradiol or progesterone

Abstract

Listen

Translate article

Doses of 100 mg of micronized progesterone (P) and of 0.5 mg of micronized estradiol (E 2) were administered vaginally and orally, respectively, in the early follicular phase of the menstrual cycle in six premenopausal women. In the second cycle, the same doses were administered in the same subjects, orally for P and vaginally for E 2. Serial blood samples were collected and the following steroids were assayed by highly reliable techniques: P, E 2, estrone (E 1), deoxycorticosterone (DOC), 5α- and 5β-pregnanolone and the sulfates of E l, E 2, and DOC. Circulating P and E 2 levels were higher after vaginal than after oral administration, while those of E 1 were similar after either route. Metabolites of P (DOC, DOCS and pregnanolone) were higher after oral administration. Concerning estrogen sulfates, E 1S concentrations were similar whichever the route, while those of E 2S were lower after oral than after vaginal administration. This study has confirmed that metabolism of ingested P and E 2 occurs mainly in the intestine. Moreover, P was predominantly metabolized to 5α-reduced derivatives, whatever the route of administration. In view of the metabolic pathways which are operative and of the peripheral plasma levels which were found, the vaginal route appears to be more adequate than the oral one for hormone replacement therapy.