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Antiproliferative effects of low-dose micronized progesterone
1Department of Obstetrics and Gynecology, Jones Institute for Reproductive Medicine, Eastern Virginia Medical School, Norfolk, USA.
Objective:
To study the pharmacodynamic effects of oral micronized P on endometrial maturation.
Design:
This was a controlled, open, parallel group, pilot study.
Setting:
The experiment was performed in an outpatient academic clinical research unit.
Patients:
Twelve healthy, P-challenged, estrogen-primed, postmenopausal women participated in the study.
Interventions:
Patients were given 300 mg micronized P daily (8:00 A.M.) or twice (8:00 A.M. and 4:00 P.M.) daily from study days 1 through 14 after estrogen priming for 30 days. Blood samples were taken at 0, 0.5, 1, 1.5, 2, 3, 4, 6, and 8 hours after the 8:00 A.M. dose on study day 1 and 14 and again at 8:00 and 9:30 A.M. on days 3 and 5 fasting, days 7 and 9 after a fatty meal, and day 11 after a high fiber meal. Endometrial biopsies were taken on day 1 and 14.
Main Outcome Measures:
Progesterone concentrations were measured. Endometrial biopsies were studied for effects on histology, glycogen content of glands, ribosomal RNA, and nuclear estrogen receptors in glands, surface epithelium, and stroma.
Results:
Day 1 and 14 P kinetics were similar for 8 hours. Dose-dependent increases in glandular glycogen, decrease in ribosomal RNA, and decrease in nuclear estrogen receptors were demonstrated.
Conclusions:
Oral micronized P can induce antiproliferative changes in the human endometrium at doses lower than those required for transformation of the endometrium to a full secretory state.