CLIMACTERIC 2005;8(Suppl 1):3–63
"Even though there is a significant correlation between
the serum concentrations of estradiol and their
clinical effects, e.g. on hot flushes or bone mass,
the serum level of an individual woman does not
predict the therapeutic effect."
"the number of hot flushes differs largely in
patients who showed identical estradiol levels
during transdermal hormone therapy1. This casts
considerable doubts on the usefulness of regular
measurements of hormone levels for the prediction
or control of a therapeutic success."
In other words, individuals may respond differently to similar levels so that aiming for a certain range, sometimes quite narrow, may not be useful. Sensitivity of each varies. I may respond well to lower levels where some may need higher levels.
Horm Metab Res. 1994 Sep;26(9):428-31.
"In addition, pseudopregnancy may be useful and effective in osteopenia and lacking secondary sexual development due to gonadal dysgenesis like in Ullrich-Turner syndrome (after completion of growth), where substitution doses of ovarian hormones may be not sufficient enough to guarantee satisfactory response."
Confirming that some may need much more to respond optimally.
Also,
Maturitas, 12 (1990) 171-197
"When the serum concentrations of natural or synthetic sex steroids are measured
at short time-intervals after administration and repeatedly during long-term
treatment, it becomes obvious that there are large intra-individual and interindividual
variations. This holds true for both the contraceptive steroids and the natural
oestrogens and does not apply solely to the oral route. Long-term studies
indicate that an important influence is exerted by predisposing factors, particularly
the metabolic capacity of the liver, on the pharmacokinetics of sex steroids.
Large variations in oestradiol and oestrone levels can be observed in an individual
woman from day to day or from hour to hour, even during transdermal therapy
with oestradiol, indicating short-lived alterations in the inactivation rate
rather than changes in the release rate from the dermal reservoir.
Bypassing of the first-pass effect using parenteral routes of administration"
Hence, further supporting the idea that measuring levels is inaccurate.
Lastly,
High levels are not a good predictor of risk, rather the type of estrogen is and the route.
Am J Obstet Gynecol. 1993 Dec;169(6):1549-53.
"As serum estradiol levels increased throughout each phase (maximum mean estradiol 739.8 pg/ml)"
"Down-regulation of the fibrinolytic system was observed as estradiol levels increased. However, thrombin formation did not change, thus suggesting that elevated circulating estradiol alone does not predispose to a thromboembolic event."
Thromb Haemost. 2001 Apr;85(4):619-25.
"the oral route of estradiol administration rather than the circulating free estradiol concentration is critical for any changes to be observed."
