Expression of sex hormone-binding globulin mRNA in uterine leiomyoma, myometrium and endometrium of human subjects.

This study was designed to evaluate the effect of sex hormone-binding globulin (SHBG) on the estrogen-dependent growth of human uterine leiomyoma. Levels of SHBG mRNA were analyzed using competitive reverse transcription-polymerase chain reaction-Southern blot analysis (RT-PCR-SBA). In normal uterine endometria, the levels of SHBG mRNA in the early/mid and late proliferative phases of the menstrual cycle were significantly lower than in the secretory phase (p < 0.01). In uterine myometria and leiomyomas, SHBG mRNA level showed no significant differences during the menstrual cycle, while the ratio of leiomyoma SHBG level to the corresponding myometrium SHBG level was >1 in 21 out of 23 cases (91%). Our results suggest that steroidal regulation of intracellular SHBG synthesis in the myometrium and the leiomyoma might differ from that in the endometrium, and that the mechanism of SHBG expression in leiomyoma might, in the process of tumorigenesis, be altered from that of corresponding normal myometrium, contributing to SHBG overexpression and the abundant estrogen supply.