Enzyme immunoassay for the in vitro diagnostic quantitative measurement of active free Estradiol, an estrogenic steroid, in saliva. Results may be used in the diagnosis and treatment of various hormonal sexual disorders and in assessing placental function in complicated pregnancy.
Estradiol (1,3,5(10)-estratriene-3,17Beta-diol; 17Beta-estradiol; E21) is a C18 steroid hormone with a phenolic A ring. This steroid hormone has a molecular weight of 272.4. It is the most potent natural Estrogen, produced mainly by the Graffian follicle of the female ovary and the placenta, and in smaller amounts by the adrenals, and the male testes (1 -3)
Estradiol (E2) is secreted into the blood stream where 98% of it circulates bound to sex hormone binding globulin (SHBG) and to a lesser extent to other serum proteins such as albumin. Only a small fraction circulates as free hormone or in the conjugated form (4,5). Estrogenic activity is effected via estradiol-receptor complexes which trigger the appropriate response at the nuclear level in the target sites. These sites include the follicles, uterus, breast, vagine, urethra, hypothalamus, pituitary and to a lesser extent the liver and skin.
In non-pregnant women with normal menstrual cycles, estradiol secretion follows a cyclic, biphasic pattern with the highest concentration found immediately prior to ovulation (6,7). The rising estradiol concentration is understood to exert a positive feedback influence at the level of the pituitary where it influences the secretion of the gonadotropins, follicle stimulating hormone (FSH), and luteinizing hormone (LH), which are essential for follicular maturation and ovulation, respectively (8). Following ovulation, estradiol levels fall rapidly until the luteal cells become active resulting in a secondary gentle rise and plateau of estradiol in the luteal phase. During pregnancy, maternal serum Estradiol levels increase considerably, to well above the pre-ovulatory peak levels and high levels are sustained throughout pregnancy (9).
The DRG Salivary Estradiol ELISA kit is based on the competition principle and the microplate separation.
An unknown amount of Estradiol present in the sample and a fixed amount of Estradiol conjugated with horse-radish peroxidase compete for the binding sites of a polyclonal Estradiol antiserum coated onto the wells.
After two hours incubation the microtiter plate is washed to stop the competition reaction. Having added the substrate solution the concentration of Estradiol is inversely proportional to the optical density measured.