Differential reduction in the volume of leiomyoma and uterus during buserelin treatment

Twenty-four women (mean age 42.0 +/- 2.4 years) with leiomyoma underwent treatment with a gonadotropin releasing hormone (GnRH) agonist (buserelin) for 6 months at a dose of 1200 micrograms daily intranasally for the first 2 months, followed by 900 micrograms daily for 4 months. The volume of the uterus and of individual leiomyomas were measured by echosonography before treatment, every 2 months during treatment, and every 2 months for 6 months after cessation of therapy (a total of 7 evaluations). A control group, comprising 14 women with untreated leiomyoma, underwent ultrasound scanning every 2 months for 6 months. A significant reduction in the volume of the uterus and leiomyomas was observed after the first 2 months of treatment in all but one patient. Leiomyomas showed a greater reduction in volume (54.6 +/- 2.2%) than did the uterus (41.8 +/- 2.3%; p = 0.0003). They also showed a more rapid increase in volume after cessation of therapy (p = 0.03). The control group showed an insignificant increase in the size of the uterus and individual leiomyomas over the 6 months' monitoring. The differences observed in reduction of the volumes of the leiomyomas and the uterus during the state of hypoestrogenism induced by buserelin, as well as in their regrowth after cessation of treatment, can be explained by the greater number of estrogen receptors in leiomyoma tissue and a possible lower rate of conversion of estradiol into estrone.