Sex hormone-binding globulin mRNA levels in human uterine endometrium

Sex hormone-binding globulin (SHBG) is a specific steroid hormone-binding protein that plays a role in transporting dihydrotestosterone, testosterone and estradiol-17 beta (E2), altering their concentration in blood and influencing their biological action. Recently it has been reported that immunoreactive SHBG is localized in target tissues and that SHBG mRNA was identified in human endometrial and prostatic cell lines. In the present work, SHBG mRNA was detected in human normal endometrial tissues using Northern blot analysis and polymerase chain reaction. Its level was higher (p < 0.02) in the secretory phase than in the proliferative phase. In the secretory phase, the endometrial SHBG mRNA level was correlated positively with serum E2 and progesterone level (p < 0.05). However, there was a negative correlation between endometrial SHBG mRNA level and serum E2/progesterone ratio (p < 0.01). These findings suggest that SHBG is synthesized in the uterine endometrium and a part of its synthesis is regulated complexly by sex steroid hormones such as E2 and progesterone.