Growth factors and cytokines in uterine leiomyomas.

Uterine leiomyomas, hard masses of smooth muscle-like tissue embedded in the myometrium, may be the most common tumors among humans. These tumors enlarge in as many as 30% of women over 30 years of age, cause significant morbidity, and are the most frequent indication for hysterectomy. Many researchers and clinicians have recently directed their attentions to understanding the etiology of these benign tumors, the conditions which cause their enlargement, and appropriate therapies which may be used as alternatives to hysterectomy. The ovarian steroid hormones estrogen and progesterone are known to play a central role in the pathology of leiomyomas. Both estrogen and progesterone contribute to the pathology of leiomyomas through gene regulation, but in opposing ways. During the follicular phase, estrogen maintains high expression of several genes which are normally expressed in the differentiated myometrium of pregnancy. During the luteal phase, progesterone can increase the mitotic activity of leiomyomas, particularly in younger women. Progesterone may act by inducing the production of growth factors and/or their respective receptors. This article surveys growth factors which may promote enlargement of susceptible leiomyomas. A potential role for cytokines in leiomyoma pathology is also discussed.