Estradiol (17β-estradiol; E2; 1,3,5(10)-estratriene-3,17β-diol) is one of the three main estrogenic steroid hormones present in humans. It is the most active naturally secreted estrogen. (1) In menstruating women, estradiol is produced primarily by the ovarian follicles from testosterone, with additional amounts produced by extraglandular conversion of testosterone in peripheral tissues. (1,2,3,4) Concentrations peak mid-cycle, marking ovulation, followed by a rapid decline with a smaller secondary increase during the luteal phase. (5,6) In women of reproductive age, estradiol exhibits a diurnal rhythm where the peaks tend to occur in the early morning; the timing of the peaks is shifted later during the menstrual phase. There are also ultradian harmonics superimposed upon the basic diurnal rhythm. (7) In post-menstrual women, small amounts of estradiol continue to be made from estrone and testosterone in the peripheral tissues, but estrone, also produced peripherally, replaces it as the predominant form of estrogen. (8,9) In women, estradiol is responsible for the development of secondary sexual characteristics, enhancing breast development and affecting body shape, bones, joints, and fat deposition. (10)
In men and pre-pubertal children, estradiol originates principally from extraglandular conversion of androgens; men also have small amounts produced in the testes. (11,12) In men there is no diurnal rhythm to estradiol production. (13)
In addition to its role in sexual and reproductive functioning, estradiol also affects other parts of the body, including the cardio-vascular system, the brain, and the immune system. (14,15,16,17) Estradiol also has also been studied for strong relationships with cancers of the breast, ovary, and uterine lining. (18,19,20)
In the blood only 1 to 15% of estradiol is in its unbound or biologically active form. The remaining estradiol is bound to serum proteins. Unbound serum estradiol enters saliva via intracellular mechanisms, and in saliva the majority of estradiol remains unbound to protein. (21) The correlation between serum and saliva samples is high. (22,23,24)
The effects of freeze thaw on most biological measures, regardless of biospecimen type, can be dramatic. Analytes in oral fluid are not distinct or different in this way. As a general rule, multiple freeze-thaws should be avoided. The most practical way to address this concern is by aliqouting samples after collection. Some analytes are more resistant to freeze thaw than others. We recommend that investigators consult the literature for the analytes of interest. If there is freeze thaw data for a specific biological measure in traditional biospecimens, it is reasonable to assume this would also be true for saliva.
No, but the literature is rather extensive on this subject for several salivary analytes; especially for salivary alpha-amylase and cortisol. We do not track that information internally.
With modern search tools online, we no longer maintain records of this type. We suggest that you use Pubmed or Psychlit to search the literature or you can Ask An Expert and we will be happy to assist you in your search.
If the analyte you are interested in is not noted in our website, please contact Dr. Granger at [email protected] to find out what developments are in the pipeline.
Salimetrics does not release products for sale if the quality control (QC) testing shows any issues. Here are some probable causes:
1) Can timing of adding reagents be off? For instance with a multichannel you can pipette the conjugate and TMB so many times before you refill, but you can pipette the stop twice as fast because it is a smaller volume. If you do this, it shortens the time the bottom rows have with TMB.
2) Can your washer be uneven and sheering off antibody in the bottom corner? Aspirate and check the amount of fluid left. It should be even in all wells and no wells should be completely dry.
3) Are you mixing faster than recommended? Or slower?
4) Are all reagents completely at room temperature? A bottle of assay diluent takes 2 hours to come to RT. You can pour some off into a smaller tube to warm up quicker for the zero and nsb.
5) Are you leaving the plate come to room temperature BEFORE opening the bag? (Otherwise moisture due to humidity may form in the wells and this is particularly a problem in this high humidity weather)
6) Are your multichannel pipettes dispensing the same amount each time reliably? We discard the first and last dispenses as they are not as reliable.
7) Are you incubating with TMB in the dark? (We no longer recommend aluminum foil.)
8) Are you testing one plate at a time? For example, do not put the standards on 5 plates then go back and fill in with samples. This delays the addition of conjugate to the plates.
9) Clean your plate reader filter. Dust from the lab can collect on the filter.
10) Are you adding assay diluent to the zero in sequence after the standards and not the last thing?
11) Never put the multichannel pipette tips into the wells as you can drag down standard from the wells above it causing lower readings in other wells.
12) Thoroughly blot all wells just before adding TMB but do not let the plate dry out.