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Estradiol is an estrogen, or an agonist of the nuclear estrogen receptors (ERs), the estrogen receptor alpha (ERα) and the estrogen receptor beta (ERβ). [1] [2] [6] In one study, the EC 50 Tooltip half-maximal effective concentration value of estradiol for the human ERα was 50 pM (0.05 nM) and for the human ERβ was 200 pM (0.2 nM).
In the normal menstrual cycle, estradiol levels measure typically <50 pg/mL at menstruation, rise with follicular development (peak: 200 pg/mL), drop briefly at ovulation, and rise again during the luteal phase for a second peak. At the end of the luteal phase, estradiol levels drop to their menstrual levels unless there is a pregnancy.
A higher dosage of estradiol gel containing 1.5 mg estradiol per daily application has been found to produce mean estradiol levels of 40 to 100 pg/mL and estrone levels of 90 pg/mL, while 3 mg per day has been found to result in respective mean estradiol and estrone levels of 60 to 140 pg/mL and 45 to 155 pg/mL. [15]
During pregnancy, levels of estradiol increase to very high concentrations that are as much as 100-fold normal levels. [138] [139] [140] In late pregnancy, the body produces and secretes approximately 100 mg of estrogens, including estradiol, estrone, and estriol, per day. [138]
The influence of 2 mg/day oral estradiol valerate on coagulation factors is less than that of 10 μg/day oral ethinylestradiol. [93] [26] [94] [95] [96] Oral ethinylestradiol at 10 μg/day has been found to have about 1.5- to 2.5-fold the impact of 2 mg/day oral estradiol valerate on HDL cholesterol and triglycerides.
[142] [145] The increase in risk is dependent on the duration of treatment, with more than five years (OR = 2.43) having a significantly greater risk than less than five years (OR = 1.49). [142] In addition, sequential estrogen–progestogen treatment ( OR = 1.76) is associated with a lower risk increase than continuous treatment ( OR = 2.90 ...
The four major naturally occurring estrogens in women are estrone (E1), estradiol (E2), estriol (E3), and estetrol (E4). Estradiol (E2) is the predominant estrogen during reproductive years both in terms of absolute serum levels as well as in terms of estrogenic activity.
The standard definition of a reference range for a particular measurement is defined as the interval between which 95% of values of a reference population fall into, in such a way that 2.5% of the time a value will be less than the lower limit of this interval, and 2.5% of the time it will be larger than the upper limit of this interval, whatever the distribution of these values.