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At least 19 recordsLinked to original sources
PubMed1976

Preferential binding of testosterone over epitestosterone by human plasma.

The main purpose of this study was to investigate if the specificity of the binding of testosterone to plasma proteins could be defined as a preferential binding of this steroid over epitestosterone. The amount of testosterone that is specifically bound was calculated using the formula: (see article) concentration, where "Ri" is the ratio (14C) testosterone: (3H) epitestosterone in plasma prior to centrifugation, "Ru" is the isotope ratio in the protein-free supernatant obtained after ultracentrifugation (149,000 x g, at 0 C, for 18 h) and "T concentration" is the testosterone concentration in plasma resulting from addition of (14C) testosterone, the endogenous steroids having been removed by preliminary charcoal extraction. The theoretical separation of the binding sites for testosterone into two populations, one non-specific with no preference for testosterone over epitestosterone, and another with absolute specificity for testosterone over its physiologically inactive stereoisomer, proved to be useful. Ovalbumin was found to be an example for non-specific, non-preferential binding. Determination of the ratio (14C) testosterone: (3H) epitestosterone in the successive fractions of various ultracentrifuged preparations showed a small but significant preference for (14C) testosterone by human and bovine serum albumin, while alpha1-acid glycoprotein had a preference for (3H) epitestosterone. Saturation curves showed at least two components: the first one, presumably corresponding to TeBG, had a higher affinity and lower capacity. This binding capacity can be accurately determined by extrapolation to the ordinate or the second component, a straight line corresponding to a binding of somewhat lower affinity and much larger capacity.

Blood Proteins↗
PubMed1979

Epitestosterone in the plasma of the goat during pregnancy and at parturition.

Epitestosterone, a product of the metabolism of androstenedione by the caprine placenta in vitro, is present in the plasma of the pregnant goat. The maternal concentrations of both epitestosterone and unconjugated oestrogens (mostly oestradiol-17 alpha) in the blood increased before parturition and dropped post partum. Measurement of arteriovenous differences at term indicated that epitestosterone was secreted by the uterus; its production was not dependent on the presence of corpora lutea. It is suggested that the concentration of epitestosterone (+ androstenedione + oestrogens) in maternal plasma may be used as an indicator of placental C-17,20 lyase activity; the slight rise in the concentration of these compounds prepartum suggests a relatively small increase in flow through this enzyme.

Animals↗
PubMed1991

Observations on the biological activity of epitestosterone.

Epitestosterone, a 17 alpha-epimer of testosterone is a normal constituent of body fluids in many species including man. It has long been believed that it is devoid of any biological significance. However, it is now demonstrated that in in vivo experiments on castrated male mice it counteracts the action of testosterone on androgen-dependent organs. In vitro experiments show that on the overall antiandrogenicity of epitestosterone participate true antiandrogenic action due to the binding to androgen receptors, strong 5 alpha-reductase inhibiting activity as well as a weak antigonadotropic activity. Epitestosterone is devoid of any embryotoxicity as checked by chick embryo-toxicity screening test.

5-alpha Reductase Inhibitors↗
PubMed1989

[Does epitestosterone function as an endogenous antiandrogen?].

The action of the endogenous steroid epitestosterone administered to castrated male mice substituted with testosterone propionate is manifested by reduced weight increments and a reduced relative weight of their seminal vesicles and kidneys. Epitestosterone in vitro displaces androgens from their bond with receptors in cytosol from rat prostates and markedly inhibits the testosterone transformation to the more effective androgen dihydrotestosterone. Epitestosterone can be thus defined as a true endogenous antiandrogen; to its action at the receptor level a potent inhibitory effect on 5 alpha-reductase must be added.

Androgen Antagonists↗
PubMed1979

Urinary testosterone and epitestosterone excretions in women with idiopathic hirsutism.

Urinary testosterone and epitestosterone were determined in 90 normal healthy women and in 90 women with idiopathic hirsutism, both groups aged between 16 and 46 years. Testosterone and epitestosterone excretion values were above the normal range in 27 of the 90 hirsute women (30%), and these 27 women had much more prominent hair growth than the others. When these results were statistically analysed according to the age groups or for all ages as a whole, they were found to be highly significant (P less than 0.0005). Therefore, it is concluded that the estimation of urinary testosterone and epitestosterone could be meaningfully applied to study the androgen status of hirsute women.

Adolescent↗
PubMed1989

Epitestosterone--an endogenous antiandrogen?

Epitestosterone (17 alpha-hydroxy-4-androsten-3-one), a normal constituent of human plasma and urine, prevents the testosterone induced changes in body weight and in organ weights of seminal vesicles and kidney of castrated male mice. It competes with methyltrienolone in the binding to rat prostate cytosol (Ki = 29.8 nmol.l-1. It inhibits also the activity of 5 alpha-reductase from rat prostate pellet (Ki = 1.2 mumols.l-1). Epitestosterone can be considered as a weak antiandrogen in the term of displacement of androgen from receptor binding and as an efficient inhibitor of 5 alpha-reductase.

Animals↗
PubMed1979

[Testosterone, epitestosterone and total estrogen excretion in men with cancer of certain localizations].

To obtain more insight into the problem on the concentration of active androgens in the male organism, the diurnal elimination of testosterone, epitestosterone and estrogens in the urine of male patients with cancer of the lung, urinary bladder, larynx and prostate (321 patients), in stage II--III, was estimated. In patients with cancer of the lung and urinary bladder testosterone was found to be lowered, while total estrogens--lowered or unchanged irrespective of age, a relative hyperestrogenization being noted in them. Contrary, in cancer of the larynx and prostate the male hormones were predominating over female ones (hyperandrogenization). In all the examined patients irrespective of the tumor process localization a relative or even absolute predominance of epitestosterone over testosterone was evident.

Adult↗
PubMed1989

The in vitro biosynthesis of epitestosterone and testosterone from C19 steroid precursors in the testis of the lizard Tiliqua rugosa.

The metabolism of androgens in the testis of the lizard Tiliqua rugosa has been studied in vitro by incubating cellular homogenates with radiolabeled C19-steroid substrates. The identification 17 beta-oxidoreductase and 3 beta-hydroxysteroid dehydrogenase/isomerase activities. Aromatase, 5 alpha-reductase, and 17 alpha/beta-epimerase activities were not detected. The 17 alpha-oxidoreductase activity was temperature dependent (maximal at 32 degrees), while the 17 beta-oxidoreductase activity was temperature independent. Time yield and dual-label studies indicated that testosterone biosynthesis mainly involves the 4-ene pathway (via androstenedione), whereas the formation of epitestosterone uses both the 4-ene and 5-ene (via 5-androstene-3 beta, 17 alpha-diol) pathways. The function of alternative pathways in androgen biosynthesis is discussed, as is the role of temperature in the intratesticular regulation of androgen production.

Androstenediol↗
PubMed1989

Dehydroepiandrosterone and epitestosterone in the blood of cows at term.

From Day 268 of gestation till two days after parturition blood samples were collected from the jugular vein of 5 cows with normal and 4 cows with flumethasone induced parturition and centrifuged immediately after sampling. In another experiment blood samples were taken from the jugular and uterine vein of 3 cows during the last week before normal parturition. The dehydroepiandrosterone (DHA) and epitestosterone (ET) concentrations in plasma were measured using radioimmunoassay. In the control group the DHA concentration was in the range of 2 to 5 nmol/l, ET levels varied from 4 to 8 nmol/l before term. In both groups, there was an increase in DHA concentrations during the last periparturient period whereas ET levels increased only after flumethasone induced parturition. The concentrations of both androgens declined after the expulsion of the placenta and they were higher in the uterine vein than in the jugular vein. It is concluded, that both androgens are secreted by the bovine placenta and that the delta 5-pathway of steroidogenesis is active in vivo.

Animals↗
PubMed1990

[Detection of self-administration of testosterone as an anabolic by determination of the ratio of urinary testosterone to urinary epitestosterone in adolescents].

Testing for illicit self-administration of testosterone by athletes requires quantitative analysis by gas chronomatography-mass spectrometry combined with stable isotope dilution. International Sports Authorities have adopted the ratio of urinary excretions of testosterone and epitestosterone for drug testing. This ratio is required to be under 6. The authors studied the statistical distribution of this ratio in teenage athletes and found that the likelihood of false-positive results is 15/10,000.

Adolescent↗
PubMed1990

Criteria to indicate testosterone administration.

A detection method for testosterone administration was developed using radioimmunoassay to measure the urinary ratios of testosterone (T) to epitestosterone (E) and to luteinizing hormone (LH). A comparative study of the effect on these ratios of a single intramuscular injection of testosterone heptanoate followed by stimulation with human chorionic gonadotrophin (HCG) in three normal men was undertaken. To allow immediate investigation, a commercially supplied epitestosterone antiserum was used. This study showed that both T/E and T/LH ratios could be used to detect testosterone administration, the latter also being an indicator of HCG use due to cross-reactivity with the LH antiserum. Subsequently, an epitestosterone antiserum of superior specificity was raised and used in a study to demonstrate the insignificant effect of exercise on these ratios. Finally, an intramuscular injection of a combined preparation of testosterone/epitestosterone heptanoates resulted in raised ratios of T/LH but not of T/E. This demonstrated the importance of the T/LH ratio in circumstances where the T/E ratio can be easily circumvented.

Adult↗
PubMed1978

The utility and selection of laboratory tests in the diagnosis of the polycystic ovary syndrome.

Fourteen patients with clinically diagnosed and surgically documented polycystic ovarian (Stein-Leventhal) disease (PCOD) and 16 normal control women were studied to identify the laboratory test or tests that, from the clinician's point of view, are most likely to aid in the nonsurgical diagnosis of the disease. A single random morning blood specimen was assayed in all cases for testosterone, epitestosterone, androstenedione, FSH and LH. The mean testosterone level for the PCOD patients was significantly greater (p less than 0.001) than that for the controls, with 50% of the patients showing elevated levels. Androstenedione showed a similar pattern, but mean epitestosterone levels were not significantly different from controls. FSH was not significantly different, but LH levels were significantly higher than controls (p less than 0.005), with 10 of 13 (77%) demonstrating elevated levels. A strong positive correlation was also found between the degree of virilization and the levels of LH, testosterone and androstenedione. This study suggests that the most useful diagnostic laboratory assay from a single drawing of blood is the serum LH; the only other useful test is testosterone and/or androstenedione. These data do not support other reports of elevated levels of epitestosterone or decreased values of FSH in PCOD.

17-Ketosteroids↗
PubMed1991

Human chorionic gonadotrophin and sport.

Human chorionic gonadotrophin (hCG) is a glycoprotein hormone which is produced in large amounts during pregnancy and also by certain types of tumour. The biological action of hCG is identical to that of luteinizing hormone, although the former has a much longer plasma half-life. Some male athletes use pharmaceutical preparations of hCG to stimulate testosterone production before competition and/or to prevent testicular shutdown and atrophy during and after prolonged courses of androgen administration. Testosterone administration can be detected by measuring the ratio of concentrations of testosterone to epitestosterone (T/E). An athlete is often considered to have failed a drug test if the urinary T/E ratio is greater than 6. In contrast, hCG administration stimulates the endogenous production of both testosterone and epitestosterone without increasing the urinary T/E ratio above normal values. Although the administration of hCG was banned by the International Olympic Committee (IOC) in 1987, no definitive test for hCG has been approved by the IOC. Currently, the only way of measuring small concentrations of hCG is by immunoassay, and this does not have a discriminating power as great as gas-liquid chromatography with mass-spectrometry which is necessary to satisfy IOC requirements. Extraction procedures and chromatographic steps could be introduced before using a selected immunoassay for hCG to meet these requirements.

Chorionic Gonadotropin↗