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Three Questions to the Editorials Author
Does progesterone exert stimulatory effect on uterine myoma growth?
Although the action of progesterone (P4) on uterine myoma growth is not simple, the net effect of P4 on uterine myoma growth is in favor of the increase in the proliferative activity for leiomyoma cells. P4 contributes to leiomyoma cell growth through stimulating EGF expression and to the cell survival through stimulating Bcl-2 expression and inhibiting TNFα expression in the cells. However, P4 also exerts an inhibitory effect on leiomyoma cell growth and survival through inhibiting IGF-I expression in the cells. This suggests that P4 may have dual actions on uterine myoma growth: one is to stimulate and the other is to inhibit leiomyoma cell growth.
What is the relationship in regulating uterine myoma growth between estrogen and progesterone?
Historically estrogen has been attributed to the pathogenesis of uterine myoma. However, it is now evident that P4 and estradiol (E2) act in combination to stimulate the EGF/EGF receptor system in regulating leiomyoma cell growth. E2 stimulates EGF receptor expression in the cells, while P4 stimulates EGF expression in uterine leiomyoma cells.
Do uterine myomas increase in size during pregnancy?
Although until recently it has been described in textbooks that uterine myomas increase in size during pregnancy, uterine myomas do not necessarily increase in size during pregnancy despite the increased circulating concentrations of E2 and P4. The dual actions of P4 may explain, at least in part, why most uterine myomas identified early in pregnancy remain the same size or even shrink over the course of pregnancy.