Levels of sex hormone-binding globulin and corticosteroid-binding globulin mRNAs in corpus luteum of human subjects: correlation with serum steroid hormone levels.

To understand regulation of the function of human ovarian corpus luteum by sex steroid-binding proteins, the levels of luteal intracellular sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) mRNAs and serum steroid hormones were simultaneously determined. The expression of SHBG and CBG mRNAs was detected in all samples analyzed. SHBG mRNA level was positively correlated with serum estradiol-17 beta level (p < 0.05), but not with serum progesterone level. There was a positive correlation between SHBG mRNA level and serum estradiol-17 beta/progesterone ratio (p < 0.01). On the other hand, CBG mRNA level was positively correlated with serum estradiol-17 beta and progesterone level (p < 0.01 and p < 0.01, respectively). There was no correlation between CBG mRNA level and serum estradiol-17 beta/progesterone ratio. SHBG and CBG mRNA levels were not correlated with the levels of serum testosterone, free testosterone or cortisol. These findings suggest that the synthesis of luteal SHBG and CBG is complexly regulated by estrogen and progesterone, and that SHBG and CBG interact with estrogen and progesterone, respectively, for luteal steroidal activity.