However , subgroup analyses for the estrogen dose and the progestin type in relation to changes in SHBG levels did show significant differences : COCs containing second generation progestins and /or the lower estrogen doses ( 20–25 µg EE ) were found to have less impact on SHBG concentrations .
The current literature review and meta- analysis demonstrates that COCs decrease circulating levels of total T and free T and increase SBHG concentrations .
Due to the SHBG increase , free T levels decrease twice as much as total T. The estrogen dose and progestin type of the COC do not influence the decline of total and free T , but both affect SHBG .
BACKGROUND Combined oral contraceptives ( COCs ) reduce levels of and rogen , especially testosterone ( T ) , by inhibiting ovarian and adrenal and rogen synthesis and by increasing levels of sex hormone-binding globulin ( SHBG ) .
Although this suppressive effect has been investigated by numerous studies over many years , to our knowledge no systematic review concerning this issue had been performed .
Validity of free testosterone and free estradiol determinations in serum samples from postmenopausal women by theoretical calculations.
In this study , we vali date d measurements of free testosterone ( fT ) and free estradiol ( fE(2 ) ) concentrations calculated from total serum concentrations of testosterone ( T ) , estradiol ( E(2 ) ) , and sex hormone-binding globulin ( SHBG ) , measured by direct , commercial radioimmunoassays , by comparison with reference measurements obtained by dialysis plus an in-house radioimmunoassay after extraction and chromatographic purification . The study was conducted in serum sample s from 19 postmenopausal women who were part of an ongoing prospect i ve cohort study . We also performed sensitivity analyses to examine the robustness of the theoretical calculations . Sensitivity analyses showed that in this population , competitive binding of dihydrotestosterone and total T could be ignored in the calculation of fE(2 ) , and competitive binding by dihydrotestosterone does not need to be taken into account for calculation of fT. Furthermore , variations in albumin and SHBG concentrations had negligible effects on fT and fE(2 ) calculations . Values of fT and fE(2 ) , calculated from total T and E(2 ) concentrations obtained by the same in-house radioimmunoassay used for the dialysis method , correlated highly with the measurements by dialysis ( Pearson 's coefficients of correlation above 0.97 ) . When calculating fT and fE(2 ) using total T and total E(2 ) concentrations obtained by different direct radioimmunoassays , almost all kits gave good correlations with the reference method for fT ( Pearson 's r > 0.83 ) , but only a few gave good correlations for fE(2 ) ( Diagnostic System Laboratories and DiaSorin ; r > 0.80 ) . The direct radioimmunoassays giving the best correlation for fT and fE(2 ) with the dialysis method were those that best measured total concentrations of T and E(2 ) . Furthermore , mean values of fT and fE(2 ) corresponded well to mean values by the reference method if SHBG measurements were also well calibrated . We conclude that in postmenopausal women , theoretical calculations are valid for the determination of fT and fE(2 ) concentrations and can give reliable estimation of cancer risk in epidemiological studies when the total concentrations of T , E(2 ) , and SHBG are measured accurately
However , subgroup analyses for the estrogen dose and the progestin type in relation to changes in SHBG levels did show significant differences : COCs containing second generation progestins and /or the lower estrogen doses ( 20–25 µg EE ) were found to have less impact on SHBG concentrations .
The current literature review and meta- analysis demonstrates that COCs decrease circulating levels of total T and free T and increase SBHG concentrations .
Due to the SHBG increase , free T levels decrease twice as much as total T. The estrogen dose and progestin type of the COC do not influence the decline of total and free T , but both affect SHBG .
BACKGROUND Combined oral contraceptives ( COCs ) reduce levels of and rogen , especially testosterone ( T ) , by inhibiting ovarian and adrenal and rogen synthesis and by increasing levels of sex hormone-binding globulin ( SHBG ) .
Although this suppressive effect has been investigated by numerous studies over many years , to our knowledge no systematic review concerning this issue had been performed .