Category Archives: Testosterone

Development and Validation of a Fecal Testosterone Biomarker: DISCUSSION(4)

The radioactive tracer experiment indicated substantial metabolism of the [14C]testosterone resulting in only a small percentage of injected radiolabeled testosterone being excreted in the feces. Though measurable, androsterone and etiocholanone were not good indicators of testes function, probably because these steroids are also formed as metabolites of adrenal steroid secretion. Despite the extensive metabolism of testosterone, there is sufficient amount excreted to quantify using the … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: DISCUSSION(3)

The first phase (a) corresponded to the rapidly available portion of the [14C]testosterone that went directly to highly perfused tissues such as liver and kidney. The second phase (p) corresponded to a slower component in which the testosterone is sequestered in slowly perfused tissues such as adipose tissues. Intraperitoneal dosing may favor the excretion of testosterone in one phase over another. Fecal excretion of testosterone … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: DISCUSSION(2)

Comparison of an ether extraction, with and without wetting, to a 10% methanol solubilization extraction showed that the former was the better method of extraction for unconjugated testosterone. An additional extraction with ether on the wetted sample recovered only an additional 5%, indicating this additional step was not necessary because it provided only a minor increase in extraction efficiency. Though the exact percentage of unconjugated … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: DISCUSSION(1)

The use of feces for steroid analysis enables laboratory and field data to be collected in situations in which blood and urine collection may prove either detrimental to the animal or impossible to obtain. Blood collection is an invasive technique through which only limited number of samples can be obtained from a single animal. Furthermore, fecal measurements of testosterone correlate well with measurements of plasma … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: RESULTS(4)

Analysis of the aqueous component remaining after ether extraction yielded a single large polar peak (the presumably conjugated metabolites were not enzyme hydrolyzable and were not identified). Further HPLC analyses using an in-line ra-diomatic detector on samples from Mus indicated that testosterone made up less than 8% of nonpolar steroids from feces. buy cipro Animal Validation Fecal testosterone concentrations increased to 8 times the basal … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: RESULTS(3)

In Peromyscus, an average of 72.8 ± 12.8% of the total radiolabeled steroid was recovered from each animal. The testosterone excreted into urine and feces was very consistent between the three animals injected. Of the 73% recovered, 91.8 ± 1.5% was excreted in the first 24 h (Fig. 1). The rate vs. time profile showed two elimination phases. The first phase (a phase) occurred between … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: RESULTS(2)

Extraction Efficiency The extraction of tritiated testosterone metabolites from pooled fecal samples using pentane:ethyl acetate (80:20) and ethyl ether resulted in 82% and 86% recovery, respectively. Decreasing the sample size to less than 30 mg and increasing the solvent volume to 4 ml increased the efficiency to 90%. buy birth control online Ether extraction of pooled fecal samples wetted with 10% methanol gave the highest recovery of free (ether … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: RESULTS(1)

Assay Validation The cross-reactivity of several steroids with the polyclonal antibody shows very high specificity for testosterone. The 5-reduction product of testosterone, 5-alpha-di-hydrotestosterone (5a-DHT), resulted in 57% cross-reactivity; the next highest cross-reactivity, 0.30%, was shown by androstenediol. Androsterone, dehydroepiandrosterone, estradiol , progesterone, and pregnenolone all had cross-reactivities of less than 0.04%. The bile acids had reactivities of less than 0.02%. The slopes generated from the serially … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: MATERIALS AND METHODS(9)

Animal Validation To validate the use of the biomarker for measuring changes in male reproductive condition, a fecal sample was obtained from three male Peromyscus to determine a basal testosterone level. The animals were then weighed and injected s.c. with 2.5 IU/g hCG in 0.9% sterile saline. ventolin 100 mcg Fecal samples were collected at 20, 24, and 28 h after injection to obtain the peak testosterone excreted. … Continue reading

Development and Validation of a Fecal Testosterone Biomarker: MATERIALS AND METHODS(8)

Separation of Free Steroid Samples initially extracted with 10% methanol were reextracted using ethyl ether to obtain primarily unconjugated testosterone and nonpolar metabolites of testosterone. Extracts were concentrated into 2-ml vials, dried under nitrogen, and reconstituted in ethanol. HPLC separations were obtained using a Waters 5 X 100-mm Nova-Pac C18 column contained in an RCM Radial Compression Cartridge Holder (Waters, Milford, MA). A linear gradient … Continue reading