Polysiloxane vaginal rings and cylinders for physiologic endometrial priming in functionally agonadal women

17 beta-estradiol (E2)-and/or crystalline progesterone (P)-impregnated polysiloxane vaginal rings and cylinders were tested as a system for endometrial priming in functionally agonadal women awaiting donor embryo transfer. Endometrial tissue was obtained by a transcervical biopsy procedure on simulated cycle day 26. The adequacy of the replacement regimen was judged by endometrial histologic dating, scanning electron micrographs, receptor content, and circulating E2 and P serum concentrations. Endometrial dating was consistent with cycle day 26. Electron micrographs showed normal surface characteristics. E2 and P receptor concentrations were within the normal range. Serum E2 levels were midfollicular, 105 +/- 12.8 pg/ml (mean +/- SEM), and midcycle, 254 +/- 28.6 pg/ml. P levels during the simulated follicular phase were undetectable (less than 0.2 ng/ml) but rose to a mean peak level of 17.3 +/- 1.8 ng/ml. The steroid-impregnated polysiloxane vaginal ring and cylinder system provided continuous and sustained hormone release, morphologically and endocrinologically normal endometrium, serum levels of E2 and P within the normal range for the entire menstrual cycle, and a convenient and physiologic therapeutic alternative to oral, vaginal, or intramuscular steroid replacement.