SEARCH · PubMed Health

Results for “testosterone”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources

PubMed2004

Testosterone effects on the breast: implications for testosterone therapy for women.

Androgens have important physiological effects in women. Postmenopausal androgen replacement, most commonly as testosterone therapy, is becoming increasingly widespread. This is despite the lack of clear guidelines regarding the diagnosis of androgen insufficiency, optimal therapeutic doses, and long-term safety data. With respect to the breast specifically, there is the potential for exogenous testosterone to exert either androgenic or indirect estrogenic actions, with the latter potentially increasing breast cancer risk. In experimental studies, androgens exhibit growth-inhibitory and apoptotic effects in some, but not all, breast cancer cell lines. Differing effects between cell lines appear to be due primarily to variations in concentrations of specific coregulatory proteins at the receptor level. In rodent breast cancer models, androgen action is antiproliferative and proapoptotic, and is mediated via the androgen receptor, despite the potential for testosterone and dehydroepiandrosterone to be aromatized to estrogen. The results from studies in rhesus monkeys suggest that testosterone may serve as a natural endogenous protector of the breast and limit mitogenic and cancer-promoting effects of estrogen on mammary epithelium. Epidemiological studies have significant methodological limitations and provide inconclusive results. The strongest data for exogenous testosterone therapy comes from primate studies. Based on such simulations, inclusion of testosterone in postmenopausal estrogen-progestin regimens has the potential to ameliorate the stimulating effects of combined estrogen-progestin on the breast. Research addressing this is warranted; however, the number of women that would be required for an adequately powered randomized controlled trial renders such a study unlikely.

Androgens↗

PubMed1980

Differentiation between endogenous and exogenous testosterone in human plasma and urine after oral administration of deuterium-labeled testosterone by mass fragmentography.

A mass fragmentographic method employing stable isotopically labeled testosterone was employed to simultaneously determine the concentrations of endogenous and exogenous testosterone in the urine and plasma of two healthy male volunteers. After oral administration of 20 mg testosterone-19,19,19-d3, a slight but significant amount of the deuterated testosterone appeared in the plasma and was rapidly cleared. The results show that the exogenous testosterone did not influence the plasma levels or urinary excretion of endogenous testosterone.

Administration, Oral↗

PubMed1989

Endogenous and exogenous testosterone levels after administration of deuterium-labelled testosterone propionate in hypogonadotropic hypogonadism.

A gas chromatography-mass spectrometry-selected ion monitoring technique was employed to determine simultaneously the plasma concentrations of endogenous and exogenous testosterone in three patients with hypogonadotropic hypogonadism after a single i.m. dose of testosterone propionate-19,19,19-d3. The plasma levels of testosterone-19,19,19-d3 derived from testosterone propionate-19,19,19-d3 were maintained above the normal testosterone levels (greater than 4 ng/ml) for 48 h, while the plasma levels of endogenous testosterone changed little.

Adult↗

PubMed1983

Plasma testosterone levels in adult and neonatal female rats bearing testosterone propionate-filled silicone elastomer capsules for varying periods of time.

Testosterone propionate (TP) was administered, by means of subcutaneous implanted silicone elastomer capsules, into adult and neonatal (aged 3 days) female rats. In the adult rats a dose-dependent increase in plasma testosterone was measured for capsules of three different sizes (5, 10 and 20 mm crystal length). Testosterone levels reached a peak 4-8 h after insertion (5 mm, 24.6 +/- 1.4 (S.E.M.) nmol/l; 10 mm, 34.0 +/- 3.8; 20 mm, 44.4 +/- 3.1) and returned to control levels within 4 h after removal: the calculated half-life of testosterone was 1 h for all sizes of capsule. In neonates, a capsule of 2.5 mm crystal length was removed after 4 h subcutaneous implantation (at day 3 of age) and produced peak testosterone levels of 126.2 +/- 11.8 nmol/l: the calculated half-life was 8.6 h which compared with a half-life of 48 h after a subcutaneous injection of 312 mumol TP (in 0.05 ml arachis oil) which produced peak levels of testosterone in 4-8 h of 84.6 +/- 11.8 nmol/l. Chronic implants of TP-filled capsules (2.5 mm crystal length) at 3 days of age and left in situ for 15 weeks gave a half-life of 69 h. Removable silicone elastomer capsules were found to be a versatile vehicle for the administration of TP to rats of all ages where precise hormone treatment for a known period or prolonged administration is required. The duration and magnitude of plasma hormone levels should be established by assay in an in-vivo situation.

Age Factors↗

PubMed1988

Effect of aldrin on spermatogenesis, plasma gonadotrophins and testosterone, and testicular testosterone in the rat.

Quantitative evaluation of the different varieties of germ cells at stage VII of the seminiferous epithelium cycle, namely type-A spermatogonia (ASg), preleptotene spermatocytes (pLSc), mid-pachytene spermatocytes (mPSc) and step 7 spermatids (7Sd), along with radioimmunoassay of plasma gonadotrophins (FSH and LH), testosterone and testicular testosterone were performed in Wistar rats following treatment with aldrin (polycyclic chlorinated hydrocarbon insecticide) for approximately one (13 days) or two cycles (26 days) of the seminiferous epithelium. Extensive degeneration of all varieties of germ cells at stage VII, reduction in the sperm count and significant reductions in plasma concentrations of LH and testosterone were observed following aldrin treatment. The reduction in plasma concentrations of FSH was statistically significant only after treatment for two cycles. The inhibitory effect of aldrin on plasma gonadotrophins, testosterone levels, testicular testosterone content and numbers of 7Sd and ASg was maximum after treatment for two cycles. Administration of human chorionic gonadotrophin along with aldrin treatment for two cycles partially prevented the degeneration of germ cells and enhanced testosterone production. The results indicate that aldrin may have a direct inhibitory influence on gonadotrophin release, but the possibility of a direct action of the insecticide at the level of the testes is also discussed.

Aldrin↗

PubMed1989

Testosterone concentrations in testicular interstitial fluid collected with a push-pull cannula or by drip-collection from adult rats given testosterone or aminoglutethimide.

This study was designed to investigate the differences in testosterone concentrations measured in testicular extracellular interstitial fluid obtained with a push-pull cannula or by post-mortem drip-collection. In the first experiment, testosterone-filled silicone elastomer capsules (2-16 cm lengths) or empty 2 cm capsules were implanted s.c. in adult male rats for 1 week. Animals were then anaesthetized and interstitial fluid was collected with a push-pull cannula for 1 h from one testis in each animal. Testicular and peripheral venous blood were then sampled and supernatant fluid was collected from the dispersed cells of the same testis. The contralateral testis in each animal was removed, and postmortem interstitial fluid obtained by drip-collection for 20 h at 4 degrees C. In animals given empty capsules, testosterone concentrations in drip-collected interstitial fluid were significantly (P less than 0.01) greater than testicular and peripheral venous blood levels, testicular fluid levels, and levels in interstitial fluid calculated from push-pull cannula samples. The concentrations of testosterone calculated in interstitial fluid collected with a push-pull cannula were never significantly greater than testicular venous blood levels. In animals with testosterone-filled capsules, testosterone concentrations measured in drip-collected interstitial fluid were similar to those calculated from push pull cannulae samples, and to testicular venous blood levels. In a second experiment, a group of adult male rats was pretreated with amino-glutethimide to block steroidogenesis. Two hours later, interstitial fluid was drip-collected from the testes of these animals and from a group of vehicle-treated controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoglutethimide↗

PubMed1978

Serum LH and FSH following passive immunization against circulating testosterone in the intact male rat and in orchidectomized rats bearing subcutaneous silastic implants of testosterone.

Subcutaneous Silastic implants were designed to release quantities of testosterone approximating that produced by the rat testis and appropriate testosterone treatment was found to produce a physiologic inhibition of both LH and FSH secretion in orchidectomized rats. In rats bearing such testosterone implants, intravenous injection of an ovine anti-testosterone serum (0.3 cc) was sufficient to completely abolish the inhibitory effects of the testosterone implant for a period of 3 days as judged by the development of typical post-castration increases in serum LH and FSH. When this dose of antiserum was administered to intact adult male rats, the increases in serum LH on days 1, 2, and 3 post-injection were approximately 19%, 15%, and 11% of those observed in untreated castrates. Increases in serum FSH in antiserum injected rats followed a pattern similar to that for serum LH but the response was slightly greater (19%, 23%, and 22% of the castrate response) and there was no indication of a decreasing effect during the three days following injection. In these experiments, passive immunization against testosterone in intact male rats produced a clearcut stimulation of both LH and FSH release, but produced no data to support the suggestion that the intact testis can secrete nonsteroidal compounds capable of producing a differential inhibition of FSH secretion.

Animals↗

PubMed1999

[Reference values of FSH, LH, total testosterone, free testosterone, 17-beta-estradiol and SHBG in healthy children in Zaragoza].

OBJECTIVE: Our purpose was to estimate reference values for basal serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), total testosterone, free testosterone, 17-beta-estradiol (E2) and sex steroid binding globulin (SHBG) in healthy children of Zaragoza. PATIENTS AND METHODS: The reference population consisted of healthy children between 0 and 14 years of age with normal weight and height and living in the metropolitan area of Zaragoza (Spain). It was a transversal study. Basal serum concentrations of FSH, LH and SHBG were measured by immunoradiometric assay. Basal serum concentrations of total testosterone, free testosterone and E2 were analyzed by radioimmunoassay. Reference values and ranges were estimated according to the recommendations of the International Federation of Clinical Chemistry. RESULTS: Reference values have been classified by age, sex and pubertal stage. Serum concentrations of FSH, LH, total testosterone, free testosterone and E2 increase during the first six months, remain low in infancy and rise during puberty. All of these concentrations showed marked differences according to sex. Serum SHBG levels are influenced by age and during puberty by sex. CONCLUSIONS: Differences in reference values for gonadotrophins, sex steroids and SHBG during infancy, childhood and adolescence makes it necessary for every population to establish their own reference values according to age, sex and pubertal stage.

Adolescent↗

PubMed1976

[Effect of neonatal injections of estradiol, testosterone and cryproterone acetate on plasma and testicular testosterone and on the genital system in adult male mice].

On day old male mice received a single injection of oestradiol benzoate, testosterone propionate or cyproterone acetate in order to study their action on testicular development, particularly testosterone secretion. Oestrogenization of newborn males leads, when the animals mature, to a high proportion or cryptorchidism, to atrophy of testes and seminal vesicles, and inhibition of spermatogenesis. Testosterone levels were reduced in the plasma. Testosterone propionate produced moderate reduction of testicular weight but spermatogenesis was not impaired. Plasma testosterone level was reduced. Cyproterone acetate increased significantly testicular testosterone level.

Animals↗

PubMed1979

[Testosterone and dihydrotestosterone radioimmunoassays in Müllerian ducts of control and testosterone propionate injected quail embryos (author's transl)].

Testosterone (T) and dihydrotestosterone (DHT) have been quantitated by means of radioimmunoassay in Müllerian ducts (CM) from control quail embryos (6 to 8-day male and 6 to 15-day female) and from female embryos injected with 50 nanograms of testosterone propionate (PT) on the 8th day. These hormones are demonstrable in undifferentiated CM from 6-day control embryos. In control males although a highly significant decrease of the CM weight occurs during the CM involution, the detected amounts of androgens remain at a constant level. In control females, the right CM shows a slight increase of the androgen content during the rudimentation, i.e. from day 8 on; in the left CM: the highest steroid levels are found on the 6th day; while the CM differentiate, concentrations decrease and become similar to those found in neutral tissues. Given testosterone propionate on day 8 female embryos: right CM: both testosterone and DHT levels highly increase until day 14; the CM of treated embryos contain 8 times as much steroid as control; left CM: testosterone and DHT increase after injection until day 9,5; they slightly decrease between days 9,5 and 12, and then remain constant on day 14. Differences in concentrations are highly significant between CM of control and of PT - injected embryos. It seems that the binding sites of these androgens are more numerous during the involution and that bound testosterone or DHT could take a part in CM regression in male embryos and right CM rudimentation in female embryos.

Animals↗

PubMed2006

Is it necessary to measure free testosterone to assess hyperandrogenemia in women? The role of calculated free and bioavailable testosterone.

Hirsutism in women is defined as excessive facial and/or body terminal hairs showing a masculine distribution; the condition affects approximately 7% of women of reproductive age, and chronic anovulation is a common problem for infertile couples, with a rate of 20-25%. There is a general consensus that these women should be evaluated endocrinologically, as many are found to have an androgen excess (AE) disorder. Free testosterone (FT) is the most prevalent marker in women with androgen excess, but the reference measurement procedures for FT are time-consuming and complex manual procedures that are not routinely practicable in large laboratories. Recently, models have been developed for calculating FT from total testosterone (TT), sex hormone binding globulin (SHBG), and albumin. These calculated values have been found to correlate closely with values estimated using the reference measurement procedures. This study compared measured endocrinological parameters--TT, free testosterone (aFT) by analogue ligand immunoassay method, dihydrotestosterone (DHT), dehydroepiandrosterone sulfate (DHEAS), (SHBG), And calculated parameters--calculated free testosterone (cFT), calculated bioavailable testosterone (cBT), and the free androgen index (FAI) in hirsute women and women with polycystic ovary syndrome (PCOS)--with the values in control individuals. A modified Ferriman-Gallwey score was use to describe the hirsutism pattern. No differences were observed when the measured hormone parameters were compared, while the calculated parameters were significantly increased in women in the hirsutism and PCOS groups in comparison with the values in the control group. Calculate parameters mat be more appropriate markers for assessing hyperandrogenemia in women in comparison with measured values of simple enzyme immuno-assays. These calculated values may be capable of replacing the values estimated using reference measurement procedures, so that time-consuming and complex manual procedures for measuring free testosterone with the reference methods may be dispensable in clinical practice.

Adult↗

PubMed2006

Double blind randomized placebo-controlled trial on the effects of testosterone supplementation in elderly men with moderate to low testosterone levels: design and baseline characteristics [ISRCTN23688581].

In ageing men testosterone levels decline, while cognitive function, muscle and bone mass, sexual hair growth, libido and sexual activity decline and the risk of cardiovascular diseases increase. We set up a double-blind, randomized placebo-controlled trial to investigate the effects of testosterone supplementation on functional mobility, quality of life, body composition, cognitive function, vascular function and risk factors, and bone mineral density in older hypogonadal men. We recruited 237 men with serum testosterone levels below 13.7 nmol/L and ages 60-80 years. They were randomized to either four capsules of 40 mg testosterone undecanoate (TU) or placebo daily for 26 weeks. Primary endpoints are functional mobility and quality of life. Secondary endpoints are body composition, cognitive function, aortic stiffness and cardiovascular risk factors and bone mineral density. Effects on prostate, liver and hematological parameters will be studied with respect to safety. Measure of effect will be the difference in change from baseline visit to final visit between TU and placebo. We will study whether the effect of TU differs across subgroups of baseline waist girth (< 100 cm vs. > or = 100 cm; testosterone level (< 12 versus > or = 12 nmol/L), age (< median versus > or = median), and level of outcome under study (< median versus > or = median). At baseline, mean age, BMI and testosterone levels were 67 years, 27 kg/m2 and 10.72 nmol/L, respectively.

Journal Article↗

PubMedDate not supplied

Suppression of the proliferative response of the seminal vesicles to testosterone by inhibitors of prostaglandin synthesis. Testosterone, indomethacin, and proliferation in seminal vesicles.

Effects of indomethacin (1.25 mg/kg) and aspirin (20 mg/kg) on testosterone-induced (0.25 mg/rat), and of indomethacin on dihydrotestosterone-induced (0.25 mg/rat) mitotic activity of the seminal vesicles and the ventral prostate in rats were examined. The results demonstrate that the seminal vesicles' proliferative reaction induced by testosterone was suppressed by treatment with indomethacin and aspirin; whereas, in the ventral prostate, the mitogenic effect of testosterone was not blocked by either of these inhibitors of prostaglandin synthesis. Cellular proliferation induced by dihydrotestosterone was not inhibited by indomethacin in either the seminal vesicles or the ventral prostate. These results suggest the existence of different mechanisms of proliferative reactions of the seminal vesicles and the ventral prostate to testosterone. The results further suggest an involvement of prostaglandins in the mitogenic effect of testosterone on the seminal vesicles.

Animals↗

PubMed1993

Seasonal variations in testicular LH, FSH, and PRL receptors; in vitro testosterone production; and serum testosterone concentration in adult male vizcacha (Lagostomus maximus maximus).

Seasonal changes in the reproductive activity of the adult male vizcacha (Lagostomus maximus maximus), a South American rodent, were investigated. Monthly, for 1 year, the animals were captured during the night near their burrows in the vicinity of San Luis, Argentina. The animals were killed, and samples of blood and the testes were collected. The testosterone serum levels were determined and the testicular tissue was used for biochemical and structural studies. Significant changes associated with seasonal cycles were found. In July-August (winter in South America), a short hibernal period of sexual quiescence, decline in testicular volume, and a significant decrease in serum testosterone were observed. The in vitro testosterone production and testicular LH, FSH, and PRL receptors revealed a significant decrease during this period. During September-November (spring season), recovery was observed, with a significant increase in gonadal activity during April-May (autumn season). During this season, the gonadal volume was increased, the serum testosterone and the in vitro stimulation of testosterone production by hCG (as well as the basal levels) also revealed a significant increase. Correspondingly, the concentration of testicular LH, FSH, and PRL receptors was elevated. These results indicate an increase in parameters related to testicular function. A gradual reduction in the testicular activity was observed in June-July (early winter). Our findings indicate that the male adult vizcacha, under natural conditions, exhibits characteristics of an annual reproductive cycle.

Animals↗

PubMed1993

Effects of high doses of testosterone propionate and testosterone enanthate on rat seminiferous tubules--a stereological and cytological study.

The effects of exogenous testosterone on various testicular variables has become of increasing significance because of its potential use in male contraception. For this reason, high doses of two testosterone esters [testosterone propionate (TP) and testosterone enanthate (TE)] were used in a study of their influence on the morphology, length and curvature of the seminiferous tubules of the rat testis, and on cytological smears of the seminiferous tubules epithelium. TP was given for 14 days (3 mg/100 g body weight, i.m.) to assess the acute effects of testosterone on the seminiferous tubules. TE was administered for 60 days (in the same manner as TP) to study possible chronic effects on the rat testis. After TP and TE treatment the seminiferous tubule epithelium showed disorganization and desquamation of spermatogenic cells. In the TP-treated testes the tubules lined with Sertoli cells only were observed. The values for the length and curvature of seminiferous tubules of the TP- and TE-treated rats were significantly reduced (p < 0.001). All these changes were observed earlier in the TP-treated than in the TE-treated animals. In cytological smears of the testis of the TP- and TE-treated rats an increase of vacuoles and residual bodies in Sertoli cell cytoplasm was noted. In addition, a reduction of spermatogenic cells, particularly sperms, was manifest in the smears after treatment. Large groups of Sertoli cells were seen in the smears from these testes.

Animals↗

PubMed1983

Binding capacity of testosterone-estradiol-binding globulin (TeBG), total and calculated unbound concentrations of testosterone in patients with carcinoma of the prostate treated with orchidectomy or estrogens.

Testosterone-estradiol-binding globulin (TeBG) binding capacity, total estradiol-17 beta and total testosterone were measured in patients with carcinoma of the prostate treated with orchidectomy or estrogens. Comparisons were made with a control group. There was a significant increase in TeBG binding capacity in the group treated with estrogens. Both orchidectomy and estrogen-treatment decreased total testosterone significantly and to the same degree. The concentration of free testosterone was calculated using a new method, and was found to be lower in orchidectomized and estrogen treated patients when compared with the control group. When the two groups under treatment were compared, the calculated free testosterone concentration was significantly lower in the estrogen treated group.

Adenocarcinoma↗

PubMed1985

A study of 19-O-carboxymethyl ether and 19-hemisuccinate derivatives of testosterone: their immunogenicity and use as iodinated radioligands for radioimmunoassay of testosterone.

Testosterone 19-O-carboxymethyl ether (T19C) and 19-hemisuccinate (T19H) derivatives were synthesised, and coupled to bovine serum albumin (BSA) or porcine thyroglobulin (PT) for immunogens or to iodohistamine for radioligands. The immunogenicity of these conjugates in mice was compared with those of testosterone 3-O-carboxymethyloxime and 15 beta-thioethyl conjugates. Of 10 immunogens studied, those linked to PT gave the highest antiserum titres and more sensitive standard curves. The site of conjugation (19 or 3 position) had little effect on immunogenicity. Cross-reactivity with 5 alpha-dihydrotestosterone (DHT) was in the range 22-100%, for the 19-linked immunogens. Antisera to T19C and T19H conjugated to PT were then raised in rabbits and characterised with 4 radioligands. Homologous assay systems in which the chemical bridge was identical in immunogen and 125I-radioligand gave the highest antiserum titres but the poorest assay sensitivity while those heterologous with respect to bridge or site gave the most sensitive standard curves. Rabbit antisera to both T19C and T19H immunogens showed good specificities with respect to DHT (range of cross reactions 0.78-21.1%), androstenedione, AN (range 0.45-2.3%) and progesterone, Po (range 0.05-1.4%) with all radioligands. The best assay system employed an antiserum to the T19H-PT immunogen with heterologous radioligand [125I]T19C. It had a detection limit of 15pg/tube and low cross-reactivity with DHT (0.78%), Po (0.3%) and AN (0.43%). We conclude that 19-linked derivatives of testosterone conjugated to PT are good immunogens and the antisera when combined with [125I]testosterone radioligands which are heterologous with respect to the chemical bridge, provide highly specific assays for testosterone with potential for clinical application.

Animals↗

PubMed1986

A new method for the simultaneous determination of androstenedione, testosterone, 11-oxotestosterone and 11 beta-OH-testosterone in fish plasma using combined techniques of Celite chromatography and radioimmunoassay.

A new method for the simultaneous determination of androstenedione, testosterone, 11-oxotestosterone and 11 beta-hydroxy-testosterone in teleost plasma has been developed. Steroids extracted from the plasma were first separated by Celite chromatography using ethanediol as the stationary phase and different concentrations of ethyl acetate in iso-octane as the eluting solvents. Androstenedione, testosterone, 11-oxotestosterone and 11 beta-OH-testosterone were eluted successively with 0, 10, 15 and 40% of ethyl acetate in iso-octane. The eluted steroid fractions were then quantatively determined by radioimmunoassay. Data on the accuracy, precision, and sensitivity were presented showing that this new assay system was precise and reproducible. As an illustration of its application, this method was used in the present study to determine the plasma androgen levels in Monopterus albus and in methyl-testosterone treated Tilapia mossambicus.

Androstenedione↗