Effect of estriol administration on the hypogonadal woman.

Authors: Schiff I, Wentworth B, Koos B, Ryan KJ, Tulchinsky

Publication Year: 1978

Citation: Fertil Steril. 1978;30(3):278-82.

Vaginal or oral estriol (0.5 mg) was given to 14 postmenopausal women.  When given orally, the estriol was rapidly conjugated, so that most of the estriol was present in a non-biologically active form in the blood.  Vaginal treatment resulted in less rapid conjugation, making it more biologically available.  Estrogenic effects were observed on the vaginal lining with both treatment forms.  Serum levels of unbound estriol after a month of oral treatment were similar to those seen 3 hours after vaginal application of 1/16 of the oral dose.  Continuous oral administration of estriol increases its potency, while much lower doses can be used vaginally to achieve similar biological effects.

http://www.ncbi.nlm.nih.gov/pubmed/710598