The distribution of endometrial leukocytes and their proliferation markers in trimegestone-treated postmenopausal women compared to the endometrium of the natural cycle: a dose-ranging study.

The effect of trimegestone-based sequential hormone replacement therapy (HRT) on the distribution of endometrial leukocytes and Ki-67 expression was investigated and the findings compared with the endometrium of the natural cycle. Endometrial cells positive for CD45(+), CD56(+), CD3(+), Ki-67(+) and CD45(+)/Ki-67(+) antigens were immunohistochemically evaluated in samples from postmenopausal women who completed a randomized, double-blind, dose-ranging study of oral trimegestone (0.05, 0.1, 0.25 and 0.5 mg per day) from days 15 to 28 with continuous micronized oestradiol 2 mg daily for six treatment cycles. The control samples were luteinizing hormone (LH)-dated endometrial biopsies. Cell counts were interpreted using linear discriminant analysis and unpaired t-test. The dose of trimegestone did not significantly affect the mean count of CD45(+), CD56(+), CD3(+), Ki-67(+) and CD45(+)/Ki-67(+) cells in the endometrial biopsies obtained from treated women. Endometrial sections from women who bled on the day of the biopsy contained higher numbers of CD45(+) and CD56 cells. In the trimegestone-treated endometrium, CD45(+), CD56(+) and CD3(+) cell expression was similar to the proliferative and early secretory phases of the natural cycle. However the expression Ki-67 and CD45(+)/Ki-67(+) cells was similar to the menstrual phase of the natural cycle endometrium. Women treated with four doses of trimegestone exhibited four different bleeding patterns. Therefore the endometrial infiltration with these cells did not explain the pattern of bleeding in women on this HRT regimen.