Testosterone is an anabolic steroid hormone synthesized from androstenedione in the Leydig cells of the testes of males and, in smaller quantities, in the ovaries of females. (1) Small amounts are also secreted by the adrenal glands in both sexes. In both men and women a large portion of total testosterone production occurs in peripheral tissues by conversion of circulating DHEA-S, DHEA, and androstenedione. In post-menopausal women, the ovaries and peripheral tissues continue to produce testosterone and other androgens, which then serve as precursors for the synthesis of estradiol in the peripheral tissues. The conversion of precursors into testosterone and the estrogens in peripheral tissues allows these steroids to be delivered to the appropriate tissues without leakage of significant amounts into the circulation, avoiding undesirable effects of high circulating levels. (2,3,4) Testosterone exhibits a diurnal rhythm, with highest levels in the morning and a nadir around midnight. (5,6)
In men, testosterone plays an important role in the development of male reproductive tissues including the testis and prostate, as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and hair growth. (7,8) Additionally, testosterone is essential for health and well-being, stamina, sexual function, cardiovascular health, and immune protection. (9,10,11,12) Testosterone measurements are typically used for clinical evaluation of hypogonadism in males and hyperandrogenic states in females. (13,14,15)
In blood, only 1 to 15% of testosterone is in its unbound or biologically active form. The remaining testosterone is bound to serum proteins. Unbound testosterone enters the saliva via intracellular mechanisms, and in saliva the majority of testosterone is not protein-bound. (16) The serum-saliva correlation for testosterone is very high for males, but only modest for females, possibly because women’s values often fall near the bottom of the measurable range for both serum and saliva immunoassay kits. (17,18)
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.