[Uterine leiomyoma: pathogenesis and treatment].

The pathogenesis of uterine leiomyoma is controversial. Studies on the development of smooth muscle cells in the endoderm-derive ducts (digestive and urinary tracts) and in the mesoderm-derived ducts (mullerian duct) during the fetal period revealed that the development of smooth muscle in the mesoderm-derived ducts (until at least 30 weeks of gestation) is slower than that of smooth muscle in the endoderm-derived ducts (until 12 weeks of gestation). The undifferentiated cells which proliferate and differentiate into smooth muscle in the uterus during the fetal period thus have a longer duration of unstable period being affected by many maternal environmental factors such as sex steroids and/or growth factors. The undifferentiated cells affected by some unknown maternal factors during the fetal period probably become the progenitor cells of leiomyomas. The progenitor cells of leiomyomas probably reside in the myometrium and begin to grow after menarche, and thrive during the years of greatest ovarian activity under the hormonal influence of both estrogen and progesterone, and following the menopause, with regression of ovarian steroids, growth of leiomyomas usually ceases. The growth pattern of leiomyomas indicates that LH-RH analogue, which induces temporal regression of ovarian steroids, becomes one of candidates for the conservative treatment of uterine leiomyomas. However, if we may treat leiomyomas with drugs, the definite diagnosis of uterine leiomyoma is essential. Magnetic resonance imaging (MRI) is a powerful diagnostic method for uterine leiomyomas. MRI gives us an information of the location and numbers of leiomyoma in the uterus. Moreover, it also informs us the characteristics of leiomyomas.(ABSTRACT TRUNCATED AT 250 WORDS)