Androstenedione (4-androstenedione; 4-dione; 4-androstene-3,17-dione) is a steroid hormone produced in the adrenal glands and the gonads. (1,2,3) It is synthesized from DHEA or 17OH-progesterone, and it serves principally as the immediate precursor compound that is converted into testosterone or estrone, both of which may then be further converted into estradiol. (4) The same sequence of conversion of DHEA and androstenedione into other steroids also takes place in many peripheral tissues throughout the body, allowing androgens and estrogens to be delivered to the appropriate tissues without leakage of significant amounts into the circulation. (5,6) Levels of androstenedione begin to increase in children at about age 6-8, and it serves as the main source of androgens prior to gonadarche. (7) High levels of androstenedione may confer androgenic risk, especially in females, and estrogenic risks, especially in males. Children and adolescents are particularly vulnerable to the effects of androstenedione conversion to active sex steroids.
These effects may disrupt normal sexual development, specifically virilization in girls associated with severe acne, excessive body hair, disruption of the menstrual cycle, and infertility. The conversion of androstenedione to estrogens can cause feminization of boys. (8,9) Elevated levels have been associated with disruptive behavior disorders in children. (7) Measurement of serum androstenedione is used as a marker of androgen biosynthesis. High circulating androstenedione levels are indicated in virilizing congenital adrenal hyperplasia, polycystic ovarian syndrome, and other causes of hirsutism in women. Elevated androstenedione levels may also occur as a result of adrenal or ovarian tumors. (10,11) Androstenedione exhibits a diurnal rhythm similar to that of cortisol, with highest levels in the morning and a nadir in the late evening. (12,13)
In blood, androstenedione is not strongly bound to sex hormone binding globulin (SHBG) or albumin. Approximately 95% of circulating androstenedione is available to tissues. (14) Unbound androstenedione enters saliva from blood via intracellular mechanisms, and the correlation between serum and saliva values is highly significant. (15)
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.