Estradiol

Estradiol
Estradiol is the most potent estrogen of a group of endogenous estrogen steroids which includes estrone and estriol. In women estradiol is responsible for growth of the breast and reproductive epithelia, maturation of long bones and development of the secondary sexual characteristics. Estradiol is produced mainly by the ovaries with secondary production by the adrenal glands and conversion of steroid precursors into estrogens in fat tissue.

During the early part of the menstrual cycle, estradiol levels remain nearly constant. This is followed by a rapid increase reaching a peak the day before or the day of the Leutinizing Hormone (LH) surge (ovulation). It is generally believed that the rise in estradiol is the factor which triggers LH release. Following ovulation there is a drop in estradiol followed by a second rise which corresponds with the formation of the corpus luteum.

At menopause, estrogen concentrations in the body fall to low levels. This decrease is often accompanied by vascular instability (hot flashes and night sweats), a rise in incidence of heart disease, and an increasing rate of bone loss (osteoporosis). Estrogen replacement for alleviation of menopausal symptoms or to prophylax against heart disease and osteoporosis has become very common.

Estradiol levels are used to assess fertility, amenorrhea and precocious puberty in girls. Measurement of estrogen levels is also useful to monitor and titrate replacement therapy especially when the endpoints are long term health (reduction in heart disease and osteoporosis) rather than the immediate relief of symptoms.

Interpretation of Results
Salivary levels of naturally produced hormones reflect the free fraction (non-protein bound fraction) of the hormone in the blood. Levels are about 1% of the total serum concentration (although individual variability is relatively broad). Salivary levels of those on oral replacement show the same pattern. Transdermal cream users show much higher saliva estradiol levels. Trough levels are just prior to next scheduled dose and were used to determine our ranges.

Ranges of estradiol in saliva for those with and without supplementation are outlined below. Estradiol is measured in pg/ml.

Endogenous Supplemented

Premenopausal                                 Oral Replacement*          2 - 20
    follicular         0.5 - 5
    midcycle          3 - 8                      Pharmaceutical Patch*     1 - 5
    luteal             0.5 - 5
                                                        Transdermal Cream*      10 - 50
Postmenopausal    <1.5

*Ranges represent levels 8 - 12 hours after last dose or application.

References
1) Worthman CM, Stallings JF, Hofman LF: Sensitive Salivary Estradiol Assay for Monitorig Ovarian Function. Clin Chem 1990;36(10):1769-1773
2) Tamate K, Charleton M, Gosling JP, Egan D, et al.: Direct Colorimetric Monoclonal Antibody Enzyme Immunoassay for Estradiol-17 beta in Saliva. Clin Chem 1997;43(7):1159-1164
3) The Writing Group for the PEPI Trial: Effects of estrogen or estrogen/progestin regimens on heart disease risk factors in postmenopausal women. JAMA 1995;273:199-208
4) Ross G, Vande Wiele R, Frantz A: The Ovaries and the Breasts: Textbook of Endocrinology, 6th ed., Williams, R. (ed.) W.B. Saunders, 1981:355
5) Lipson, S & Ellison P: Development of protocols for the application of salivary steroid analysis to field conditions. American Journal of Human Biology 1989;1:249-255