Antiproliferative effects of low-dose micronized progesterone

Area of Science:

• Reproductive Endocrinology
• Pharmacodynamics
• Gynecologic Oncology

Background:

• Endometrial maturation is a complex process influenced by hormonal signaling.
• Understanding the pharmacodynamic effects of progesterone is crucial for therapeutic applications.
• Estrogen priming is a common method to prepare the endometrium for progesterone treatment.

Purpose of the Study:

• To investigate the pharmacodynamic effects of oral micronized progesterone (P) on endometrial maturation in postmenopausal women.
• To assess the impact of different dosing regimens on progesterone levels and endometrial histology.
• To evaluate changes in endometrial glycogen, ribosomal RNA, and estrogen receptors following progesterone administration.

Main Methods:

• A controlled, open-label, parallel-group pilot study involving 12 healthy, estrogen-primed, postmenopausal women.
• Participants received 300 mg of oral micronized progesterone daily or twice daily for 14 days.
• Blood samples were collected at multiple time points to measure progesterone concentrations; endometrial biopsies were analyzed for histological changes, glycogen content, ribosomal RNA, and nuclear estrogen receptors.

Main Results:

• Progesterone pharmacokinetics were consistent between day 1 and day 14 of the study.
• Oral micronized progesterone demonstrated dose-dependent effects, including increased glandular glycogen.
• Significant decreases in endometrial ribosomal RNA and nuclear estrogen receptors were observed.

Conclusions:

• Oral micronized progesterone can induce antiproliferative changes in the human endometrium.
• These effects are achievable at doses lower than those required for complete secretory transformation.
• Findings suggest potential for using oral micronized progesterone in conditions requiring endometrial modulation.