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The murine Niemann-Pick type C lesion affects testosterone production.

We have determined the effects of the Niemann-Pick type C (NPC) lesion, which impairs transport of cholesterol from lysosomes, on the androgenic status of male NPC mice. The mice have low serum testosterone levels resulting from decreased testosterone secretion. Testosterone secretion is reduced in NPC mouse testes incubated with 8-bromo-cAMP, 20 alpha-hydroxycholesterol, and pregnenolone compared to testosterone release by normal mouse testes under identical conditions. Ultrastructural examination of testes revealed a paucity of lipid droplets, extensive accumulation of inclusion bodies, and distorted endoplasmic reticulum in Leydig cells of adult NPC mice. The hypoandrogenemia caused systemic deficiencies in NPC mice. Seminal vesicles, a testosterone-responsive tissue, were underdeveloped in NPC male mice. The testosterone-responsive kidney beta-glucuronidase activity was also underexpressed. Seminal vesicle mass and beta-glucuronidase activity were increased by testosterone treatment of NPC mice. Many hepatic proteins, identified by microsequencing, were also deficient in NPC male mice. Levels of alpha 2-mu-globulin, glutathione S-transferase-pi, carbonic anhydrase-III, and selenium-binding protein increased in normal male mice during puberty, but did not increase in the NPC male mice. Based on the increases in protein expression during puberty, differential expression in males and females, and the reported involvement of androgens in regulating expression of some of these proteins, deficient expression of most of these proteins in male NPC mice appears to result from low testosterone levels. We conclude that a defect in testicular testosterone production in NPC male mice causes a pleiotropic deficiency in androgen-sensitive expression of proteins in various organs.

Aging↗

Testosterone stimulates insulin-like growth factor-I and insulin-like growth factor-I-receptor gene expression in the mandibular condyle--a model of endochondral ossification.

Puberty is associated with an increase in the plasma concentration of sex steroids, GH, and insulin-like growth factor-I (IGF-I). Gonadal steroid hormones are important for the normal pubertal growth spurt and skeletal growth. The mechanism by which gonadal steroids induce skeletal growth is still not fully understood. To better understand the direct effect sex steroids have on bone growth, we studied an isolated organ culture system of the mandibular condyle, derived from 3.5-5.5-week-old male and female mice. We found that testosterone 10(-6) M, but not estradiol, stimulated thymidine incorporation into the DNA of male-derived condyle. Three days of testosterone treatment doubled the condyle size and increased the chondroprogenitor zone, while maintaining the normal gradient of the developing chondrocytes. Immunohistochemistry and in situ hybridization techniques showed that testosterone stimulated IGF-I and IGF-I-R and their messenger RNAs (mRNAs) mainly in the mature chondrocyte layer. Immunoneutralization of IGF-I in the testosterone-treated condyle caused the disappearance of the chondroblast and young chondrocyte layers, though the progenitor cell layer remained almost unaffected. Overtreatment with testosterone (dose or duration) accelerated condylar ossification. In the presence of testosterone 10(-5) M (high dose), calcification "climbs" up to the chondroprogenitor zone, and most of the condylar chondrocytes are replaced by bone tissue. Similar changes occurred after 7 days of testosterone treatment (long duration) with 10(-6) M. In conclusion, testosterone stimulates growth and local production of IGF-I and IGF-I-R in chondrocyte cell layers of an isolated organ culture of mice mandibular condyle. Part of the effect testosterone has on condylar growth is mediated by IGF-I.

Animals↗

Effects of testosterone supplementation on skeletal muscle fiber hypertrophy and satellite cells in community-dwelling older men.

OBJECTIVE: In this study, we determined the effects of graded doses of testosterone on muscle fiber cross-sectional area (CSA) and satellite cell number and replication in older men. PARTICIPANTS: Healthy men, 60-75 yr old, received a long-acting GnRH agonist to suppress endogenous testosterone production and 25, 50, 125, 300, or 600 mg testosterone enanthate im weekly for 20 wk. METHODS: Immunohistochemistry, light and confocal microscopy, and electron microscopy were used to perform fiber typing and quantitate myonuclear and satellite cell number in vastus lateralis biopsies, obtained before and after 20 wk of treatment. RESULTS: Testosterone administration in older men was associated with dose-dependent increases in CSA of both types I and II fibers. Satellite cell number increased dose dependently at the three highest doses (3% at baseline vs. 6.2, 9.2, and 13.0% at 125, 300, and 600 mg doses, P < 0.05). Testosterone administration was associated with an increase in the number of proliferating cell nuclear antigen+ satellite cells (1.8% at baseline vs. 3.9, 7.5, and 13% at 125, 300, and 600 mg doses, P < 0.005). The expression of activated Notch, examined only in the 300-mg group (baseline, 2.3 vs. 9.0% after treatment, P < 0.005), increased in satellite cells after testosterone treatment. The expression of myogenin (baseline, 6.2 vs. 20.7% after treatment, P < 0.005), examined only in the 300-mg group, increased significantly in muscle fiber nuclei after testosterone treatment, but Numb expression did not change. CONCLUSIONS: Older men respond to graded doses of testosterone with a dose-dependent increase in muscle fiber CSA and satellite cell number. Testosterone-induced skeletal muscle hypertrophy in older men is associated with increased satellite cell replication and activation.

Aged↗

Loss of circadian rhythmicity in blood testosterone levels with aging in normal men.

Previous studies concerning the relationship of serum testosterone levels to aging in normal men have yielded apparently inconsistent results. Studies performing blood sampling in the morning have often shown an age-related decrease in testosterone levels, while those using afternoon samples have failed to show such a decrease. These results suggested to us the possibility that the circadian rhythm in serum testosterone levels might be altered with normal aging in men. Hourly blood samples were obtained for 24 h from 17 young (mean age, 25.2 yr) and 12 old (mean age, 71 yr) healthy men. Total testosterone levels were measured by RIA. The circadian rhythm in serum testosterone levels found in normal young men was markedly attenuated or absent in healthy elderly men; the early morning rise in testosterone levels characteristic of young men was not present in old age. Mean testosterone levels for the entire 24-h day were lower in healthy old men than in young men. These results demonstrate a clear decrease in serum testosterone levels in healthy old men compared to those in young men and provide an explanation for the inability to demonstrate an age-related decline in testosterone levels in earlier studies using serum samples obtained in the afternoon.

Adult↗

Somatomedin response to testosterone stimulation in children with male pseudohermaphroditism, cryptorchidism, anorchia, or micropenis.

Somatomedin-C (Sm-C) levels increase during puberty. To determine if testosterone could play a role in the pubertal Sm-C increase, 17 boys with low levels of endogenous testosterone (80 ng/dl) were studied before and 7 days after im testosterone treatment. The serum testosterone levels achieved were comparable to those found during normal puberty in most instances. After parenteral testosterone administration, serum somatomedin activity (bioassay) increased in 9 patients (from 10-56% above basal levels) and decreased in 3 (from 3.2-20.3% below basal levels); overall, there was a significant 19.2% increase (P less than 0.02). Testosterone per se did not induce an increase in bioassayable Sm, since its addition to serum failed to cause increments in activity. After im testosterone treatment, serum Sm-C levels (determined by RIA) increased in every patient studied. The mean percent increase above basal levels was 108% (range, 14-202%; n = 10; P less than 0.001). Mean serum GH increased significantly (P less than 0.05) from 4.9 ng/ml before exogenous testosterone to 12.0 ng/ml afterward. The data show that parenteral testosterone administration can increase serum Sm activity and Sm-C, probably through increased pituitary GH secretion, and this response occurs in boys ranging in age from 0.24-14.57 yr.

Adolescent↗

Effect of testosterone on metabolic rate and body composition in normal men and men with muscular dystrophy.

We have examined the effect of testosterone enanthate injections (3 mg/kg.week, im) on the basal metabolic rate (BMR) estimated by indirect calorimetry and on lean body mass (LBM) estimated by 40K counting in four normal men and nine men with muscular dystrophy. Testosterone treatment increased plasma testosterone levels in all subjects (3-fold mean elevation). BMR increased significantly after 3 months of testosterone treatment (mean, 10%; P less than 0.01; 13% mean increase in the men with muscular dystrophy and 7% mean increase in the normal subjects). BMR remained elevated (mean increase, 9%) after 12 months of testosterone treatment in four men with muscular dystrophy. LBM also was significantly higher after 3 months of treatment (mean, 10%; P less than 0.01) and remained elevated at 12 months. The percent increase in LBM was similar in men with muscular dystrophy (+10%) and normal men (+11%). When BMR was adjusted for the increase in LBM by linear regression, the men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment (mean increase, 7%), but not after 12 months. The normal men did not have an increase in adjusted BMR. Testosterone treatment for 12 months slightly reduced body fat, whereas there was an increase in body fat in subjects with muscular dystrophy who were treated with placebo for 12 months. We conclude that there is a significant increase in BMR associated with pharmacological testosterone treatment, which for the most part is explained by the increase in LBM. However, in men with muscular dystrophy, there is a small hypermetabolic effect of testosterone beyond that explained by increased LBM.

Adult↗

Amplified nocturnal luteinizing hormone (LH) secretory burst frequency with selective attenuation of pulsatile (but not basal) testosterone secretion in healthy aged men: possible Leydig cell desensitization to endogenous LH signaling--a clinical research center study.

The specific mechanisms underlying the relative hypogonadism of aging remain to be elucidated fully. We used frequent venous sampling (every 2.5 min), sensitive and specific LH and testosterone assays, and deconvolution analysis of the endocrine time series to delineate the differences between healthy young (n = 10, age 21-34 yr) and aged (n = 8, age 62-74 yr) men in the nocturnal secretion of LH and testosterone and their half-lives. We found that elderly men vs. young men had more frequent bursts of LH secretion (1.4 vs. 0.9/h, P = 0.003), less testosterone secreted per testosterone secretory burst (9.2 vs. 17.0 nmol/L, P = 0.021), and less testosterone secreted per hour (10.7 vs. 25.0 nmol/L.h, P = 0.05). As the frequency of nocturnal LH secretory bursts increased, the frequency of testosterone bursts decreased (r = -0.746, P = 0.034). We conclude that healthy aging is associated with diminished nocturnal testosterone production attributable to 1) a decrement in the mass of testosterone released per burst and 2) an inadequate response by the pituitary gland to enhance testosterone production via an accelerated LH secretory pulse frequency. We speculate that this may reflect a partial desensitization of Leydig cells to LH.

Adult↗

Testosterone replacement increases fat-free mass and muscle size in hypogonadal men.

Testosterone-induced nitrogen retention in castrated male animals and sex-related differences in the size of the muscles in male and female animals have been cited as evidence that testosterone has anabolic effects. However, the effects of testosterone on body composition and muscle size have not been rigorously studied. The objective of this study was to determine the effects of replacement doses of testosterone on fat-free mass and muscle size in healthy hypogonadal men in the setting of controlled nutritional intake and exercise level. Seven hypogonadal men, 19-47 yr of age, after at least a 12-week washout from previous androgen therapy, were treated for 10 weeks with testosterone enanthate (100 mg/week) by im injections. Body weight, fat-free mass measured by underwater weighing and deuterated water dilution, and muscle size measured by magnetic resonance imaging were assessed before and after treatment. Energy and protein intake were standardized at 35 Cal/kg.day and 1.5 g/kg.day, respectively. Body weight increased significantly from 79.2 +/- 5.6 to 83.7 +/- 5.7 kg after 10 weeks of testosterone replacement therapy (weight gain, 4.5 +/- 0.6 kg; P = 0.0064). Fat-free mass, measured by underwater weighing, increased from 56.0 +/- 2.5 to 60.9 +/- 2.2 kg (change, +5.0 +/- 0.7 kg; P = 0.0004), but percent fat did not significantly change. Similar increases in fat-free mass were observed with the deuterated water method. The cross-sectional area of the triceps arm muscle increased from 2421 +/- 317 to 2721 +/- 239 mm2 (P = 0.045), and that of the quadriceps leg muscle increased from 7173 +/- 464 to 7720 +/- 454 mm2 (P = 0.0427), measured by magnetic resonance imaging. Muscle strength, assessed by one repetition maximum of weight-lifting exercises increased significantly after testosterone treatment. L-[1-13C]Leucine turnover, leucine oxidation, and nonoxidative disappearance of leucine did not significantly change after 10 weeks of treatment. There was no significant change in hemoglobin, hematocrit, creatinine, and transaminase levels. Replacement doses of testosterone increase fat-free mass and muscle size and strength in hypogonadal men. Whether androgen replacement in wasting states characterized by low testosterone levels will have similar anabolic effects remains to be studied.

Adult↗

Long-term effect of testosterone therapy on bone mineral density in hypogonadal men.

In both men and women, a decrease in bone mineral density (BMD) is a major symptom of hypogonadism. Although the effects of estrogens on osteoporosis in women are well documented, comparatively little is known about the effects of long term testosterone substitution on BMD in hypogonadal men. Therefore, we studied BMD in 72 hypogonadal patients (37 men with primary and 35 men with secondary hypogonadism) under testosterone substitution therapy that continued for up to 16 yr. Thirty-two of these men were also seen before initiation of therapy. At annual intervals, trabecular BMD of the lumbar spine was measured by quantitative computed tomography, a true volumetric and reproducible method for long term serial BMD measurements. Serum levels of testosterone increased to the normal range in all androgen-treated hypogonadal men. The most significant increase in BMD was seen during the first year of testosterone treatment in previously untreated patients, when BMD increased from 95.2 +/- 5.9 to 120.0 +/- 6.1 mg/cm3 hydroxyapatite (mean +/- SE). Long term testosterone treatment maintained BMD in the age-dependent reference range in all 72 hypogonadal men, independent of the type of hypogonadism. Transdermal testosterone patches applied to the scrotum were as effective in normalizing BMD as im testosterone enanthate injections. In summary, testosterone therapy increases BMD in hypogonadal men regardless of age. The greatest increase is seen during the first year of treatment in previously untreated patients with low initial BMD. In hypogonadal men, BMD can be normalized and maintained in the normal range by continuous, long term testosterone substitution.

Administration, Cutaneous↗

Developmentally delimited emergence of more orderly luteinizing hormone and testosterone secretion during late prepuberty in boys.

To quantitate changing feedback control in the GnRH-LH/FSH-testosterone axis in male puberty, we here quantitate the orderliness of hormone release patterns using the regularity (pattern-sensitive) statistic, approximate entropy (ApEn), in 46 eugonadal boys representing 6 genitally defined stages of normal puberty. ApEn is a single variable, model-free, and scale-independent barometer of coordinate signaling or integrative regulation within a coupled neuroendocrine axis. Accordingly, we quantitated ApEn of LH profiles obtained by immunofluorometric assay of sera sampled every 20 min for 24 h. LH ApEn declined remarkably between early prepuberty (genital stage I-A: mean bone age, 4.6 +/- 1.6 yr; testis volume, <3 mL for at least 3 succeeding yr) and late prepuberty (genital stage I-C: bone age, 8.7 +/- 1.8 yr; testis volume, <3 mL for up to 1 yr thereafter; P: = 0.00019), which indicates the acquisition of more regular LH release patterns in late prepuberty. Maximal LH orderliness occurred in puberty stage II (bone age, 10.7 +/- 1.0 yr; testis volume, 2.8 +/- 0.4 mL). The LH secretory process was more disorderly in mid- and later puberty (Tanner stages III and IV). Transpubertal variations in testosterone ApEn manifested a similar tempo, i.e. the greatest regularity of testosterone secretion (lowest ApEn) emerged in Tanner genital stage II (P: < 10(-)(7)), with less orderly patterns evident both earlier and later in sexual development. In contrast, FSH ApEn values remained invariant of pubertal status. Analysis of bihormonal coupling using the theoretically related bivariate cross-ApEn statistic disclosed maximal 2-hormone synchrony for LH and testosterone secretion in genital stage II (P: = 0.031), with relative deterioration of coordinate LH and testosterone release patterns both before and after. LH and FSH release became maximally synchronous at the end of prepuberty (genital stage I-C; P: = 0.029), and FSH and testosterone synchrony peaked in pubertal stage III (P: = 0.037). As mean 24-h serum concentrations of LH, FSH, and testosterone rose transpubertally by 35-fold (LH), 68-fold (FSH), and 70-fold (testosterone), respectively, we infer that pubertal developmental stage per se rather than level of hormone output dictates coordinate GnRH-LH/FSH-testosterone secretion. In summary, in eugonadal boys, the regularity of 24-h LH and testosterone secretory patterns undergoes well defined pubertal stage-specific control. No sexually developmentally delimited regulation is inferable for FSH. The concept of temporally biphasic puberty-dependent variations in neurohormone secretory regularity contrasts with the unidirectional rise in daily hormone output. Accordingly, we infer that late prepuberty and early puberty (Tanner genital stages IC and II) embody a physiologically unique sexual developmental window, marked by transiently enhanced LH and testosterone feedback stability in boys. Whether analogous plasticity of hypothalamo-pituitary-gonadal interactions unfolds during female adolescence is not known.

Child↗

Disruption of the nocturnal testosterone rhythm by sleep fragmentation in normal men.

Recently, we have demonstrated that in normal men the nocturnal testosterone rise antedated the first rapid eye movement (REM) sleep episode by about 90 min and was correlated with REM latency. To further elucidate whether the diurnal testosterone rhythm is a sleep-related phenomenon or controlled by the circadian clock, we determined serum testosterone levels in 10 men during the ultrashort 7/13 sleep-wake cycle paradigm. Using this schedule, subjects experienced partial sleep deprivation and fragmented sleep for a 24-h period. Serum testosterone levels were determined every 20 min between 1900-0700 h with simultaneous sleep recordings during the 7-min sleep attempts. The results were compared with those obtained in men during continuous sleep. Although mean levels and area under the curve of testosterone were similar in both groups, fragmented sleep resulted in a significant delay in testosterone rise (03:24 h +/- 1:13 vs. 22:35 h +/- 0:22). During fragmented sleep, nocturnal testosterone rise was observed only in subjects who showed REM episodes (4/10). Our findings indicate that the sleep-related rise in serum testosterone levels is linked with the appearance of first REM sleep. Fragmented sleep disrupted the testosterone rhythm with a considerable attenuation of the nocturnal rise only in subjects who did not show REM sleep.

Adult↗

Testosterone supplementation improves spatial and verbal memory in healthy older men.

OBJECTIVE: To determine the relationship between exogenous testosterone administration and cognitive abilities in a population of healthy older men. BACKGROUND: Serum levels of total and bioavailable testosterone gradually decrease with age in men and are associated with reductions in muscle mass, osteoporosis, decreased sexual activity, and changes in cognition. METHODS: Twenty-five healthy, community-dwelling volunteers, aged 50 to 80 years, completed a randomized, double-blind, placebo-controlled study. Participants received weekly intramuscular injections of either 100 mg testosterone enanthate or placebo (saline) for 6 weeks. Cognitive evaluations were conducted at baseline, week 3, and week 6 of treatment by use of a battery of neuropsychologic tests. RESULTS: Circulating total testosterone was raised an average of 130% from baseline at week 3 and 116% at week 6 in the treatment group. Because of aromatization of testosterone, estradiol increased an average of 77% at week 3 and 73% at week 6 in the treatment group. Significant improvements in cognition were observed for spatial memory (recall of a walking route), spatial ability (block construction), and verbal memory (recall of a short story) in older men treated with testosterone compared with baseline and the placebo group, although improvements were not evident for all measures. CONCLUSIONS: The results suggest that short-term testosterone administration enhances cognitive function in healthy older men. However, it remains unclear whether these improvements in cognition are attributable to increased testosterone or estradiol levels, or both. The potential role of testosterone vs its metabolites on cognition requires further research.

Aged↗

Dehydroepiandrosterone sulphate interferes with the Abbott Architect direct immunoassay for testosterone.

BACKGROUND: There are known difficulties in measuring testosterone in women using 'direct' (non-extraction) immunoassays. The positive bias encountered in many of these assays has been attributed to an unidentified interfering substance. We have evaluated the potential for dehydroepiandrosterone sulphate (DHEA-S) to cross-react in the Abbott Architect testosterone assay. METHODS: Samples (n = 81) from female patients who had DHEA-S, direct and extracted testosterone measured were examined retrospectively. Possible cross-reactivity was evaluated by spiking both testosterone free assay diluent and serum from a woman with exogenous DHEA-S. RESULTS: The retrospective patient analysis of the data demonstrated a relationship between interference and DHEA-S (r = 0.78, P < or = 0.0001). Spiking studies revealed a linear relationship between added DHEA-S and the measured testosterone concentration. Consistent with the retrospective study, for every 1 micromol/L increase in DHEA-S, 0.23 nmol/L of testosterone was measured in the diluent. Spiking DHEA-S into serum gave only a 0.12 nmol/L increase in measured testosterone for every 1 micromol/L rise in DHEA-S. CONCLUSION: DHEA-S cross-reacts in the Abbott Architect direct immunoassay for testosterone to a clinically significant effect. This cross-reactivity is likely to be responsible for much of the interference observed when measuring testosterone in women by this method.

Cross Reactions↗

Alteration in sexually dimorphic testosterone biotransformation profiles as a biomarker of chemically induced androgen disruption in mice.

Assessment of the impact of environmental chemicals on androgen homeostasis in rodent models is confounded by high intraindividual and interindividual variability in circulating testosterone levels. Our goal was to evaluate changes in testosterone biotransformation processes as a measure of androgen homeostasis and as a biomarker of exposure to androgen-disrupting chemicals. Sex-specific differences in hepatic testosterone biotransformation enzyme activities were identified in CD-1 mice. Gonadectomy followed by replacement of individual steroid hormones identified specific sex differences in biotransformation profiles that were due to the inductive or suppressive effects of testosterone. Notably, significant androgen-dependent differences in testosterone 6[alpha]- and 15[alpha]-hydroxylase activities were demonstrated, and the ratio of 6[alpha]- and 15[alpha]-hydroxylase activities proved to be an excellent indicator of the androgen status within the animal. The male or "masculinized" testosterone 6[alpha]/15[alpha]-hydroxylase ratio was significantly less than the female or "feminized" ratio. Male mice were exposed to both an antiandrogen, vinclozolin, and to a compound that modulates serum androgen levels, indole-3-carbinol, to test the utility of this ratio as a biomarker of androgen disruption. Treatment with the antiandrogen vinclozolin significantly increased the 6[alpha]/15[alpha]-hydroxylase ratio. Indole-3-carbinol treatment resulted in a dose-dependent, but highly variable, decrease in serum testosterone levels. The 6[alpha]/15[alpha]-hydroxylase ratio increased as serum testosterone levels decreased in these animals. However, the increase in the ratio was much less variable and more sensitive than serum testosterone levels. These investigations demonstrate that the 6[alpha]/15[alpha]-hydroxylase ratio is a powerful measure of androgen modulation and a sensitive indicator of exposure to androgen-disrupting chemicals in CD-1 mice.

Androgens↗

Testosterone stimulates growth of tibial epiphyseal growth plate and insulin-like growth factor-1 receptor abundance in hypophysectomized and castrated rats.

Puberty is associated with an increase in the plasma concentration of sex steroids, growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Gonadal steroid hormones are important for the normal pubertal growth spurt and skeletal growth. The mechanism by which gonadal steroids induces skeletal growth is still not fully understood. To study the GH-independent effect of testosterone on growth, we investigated the effect of testosterone injections on the tibial epiphyseal growth plate (EGP) in an in vivo model of hypophysectomized and castrated male rats. Four groups (six animals each) of 28-d-old male rats were studied. Groups A, B, and C were hypophysectomized and castrated and received 500 microg/(kg x d) of hydrocortisone and 15 microg/(kg x d) of levothyroxine sodium. Groups A and B were also treated with daily sc injections of 10 microg of testosterone/100 g of body wt and 100 microg of testosterone/100 g of body wt, respectively, for 7 d. Group C was injected with vehicle alone. Group D were intact animals injected with saline (controls). Animals were sacrificed on 8 d. As expected, serum GH levels were found to be very low (1.13+/-0.1 ng/mL) in the hypophysectomized animals (group C, hypopit), and testosterone treatment did not change them significantly. Serum IGF-1 decreased from 502.9+/-13 ng/mL in group D to 167+/-41.4 ng/mL in group C (p < 0.001). Testosterone therapy had no stimulatory effect on serum IGF-1 levels in the hypopit + low-dose group (A) (220+/-94.8 ng/mL) and had an inhibitory effect in the hypopit + high-dose group (B) (39.3+/-17.5). Histomorphometric determinations demonstrated an EGP width of 472.3+/-39 microm in the intact animals but only 336.9+/-1.6 microm in the hypopit group (C) (p < 0.01). High-dose testosterone treatment (group B) significantly increased the EGP width (to 438.8+/-27.8), (p < 0.001), whereas low-dose testosterone (group A) did not. Immunohistochemistry studies revealed that the levels of IGF-1 in the EGP of the control animals were almost negligible and that testosterone did not change them. However, testosterone increased in a dose-dependent manner the abundance of IGF-1 receptor EGP. We conclude that testosterone has a direct, local, GH-independent effect on the EGP growth and IGF-1 receptor abundance.

Animals↗

Testosterone and estradiol have specific differential modulatory effect on the proliferation of human thyroid papillary and follicular carcinoma cell lines independent of TSH action.

Differential effects of testosterone and estradiol on the proliferation of human thyroid papillary (NPA-87-1) and follicular (WRO-82-1) carcinoma cell lines were assessed by [(3)H]-thymidine incorporation and the cell number. Cells (2.5 x 10(5)) plated in 24-well culture plates in 400 microL RPMI-1640 medium/well, under 5% CO(2) and 95= air, at 37 degrees C were exposed to exponential concentrations of human thyroid-stimulating hormone (hTSH) (1.25-640 ng/mL), testosterone (1.25-640 ng/mL), or estradiol (1.25-640 pg/mL) for 24 h. Testosterone and estradiol increased the proliferation of NPA cell line in a dose-dependent manner; flutamide (an anti-androgen) and tamoxifen (an anti-estrogen) (10(-8), 10(-7), 10(-6), and 10(-5) mol/L) effectively inhibited the testosterone and estradiol-induced cell proliferation, respectively. While flutamide inhibited the stimulatory effect of testosterone on the WRO cell line, tamoxifen augmented the inhibitory effect of estradiol. TSH did not have any effect on the proliferation of NPA or WRO cell lines, and testosterone-estradiol had no impact on TSH binding to these cells. N-ethylmalemide (5alpha-reductase inhibitor) (10(-8)-10(-5) mol/L) did not modulate basal and testosterone-induced cell proliferation, indicating the direct effect of testosterone without getting converted into dihydrotestosterone (DHT). Both the cell lines tested positive for androgen and estrogen receptors and were up-regulated by the respective ligands. It is concluded that testosterone and estradiol modify the proliferation of thyroid cancer cells through homologous up-regulation of their own receptors, which is independent of TSH, and their effects may vary according to the cell type.

Androgen Antagonists↗

Testosterone restores testicular inhibin content in cryptorchid rats.

The effects of testosterone administration on testicular inhibin content and histology were studied in bilaterally cryptorchid rats, in which a marked decrease in testicular inhibin content had been observed. Mature male Wistar rats weighing approximately 300 g were made bilaterally cryptorchid by placing the testes in the abdominal cavity. Testosterone in oil, 0.1, 1.0 or 10 mg, was given i.m. each week. Testicular inhibin and testosterone content, histology and plasma LH, FSH and testosterone were studied 2 weeks later. Abnormally decreased testicular inhibin in cryptorchidism was restored toward normal by testosterone in a dose dependent manner in 2 weeks after surgery. Sertoli cell structure also recovered toward normal with increasing amount of testosterone. Decreased testicular testosterone content and Leydig cell atrophy were observed with suppressed plasma LH and FSH after testosterone. These results showed that the increased plasma concentration of testosterone had a stimulatory effect on the Sertoli cell function in cryptorchidism, in which compensated Leydig cell failure was demonstrated.

Animals↗

The interaction of testosterone and gonadotropins in stimulating estradiol and progesterone secretion by cultures of corpus luteum cells isolated from pigs in early and midluteal phase.

The first objective of this research was to define the capacity of corpora lutea of pig to secrete estradiol in the presence of an androgen substrate which was testosterone. The second objective was to define the synergism between gonadotropic hormones such as LH, FSH, and PRL and testosterone as measured by estradiol and progesterone secretion by two types of porcine luteal cells. Luteal cells were collected from newly forming corpora lutea (0-3 days after ovulation) and from mature corpora lutea (8-10 days after ovulation). After dispersion, luteal cells were suspended in medium M199 supplemented with 10% of calf serum and grown as monolayers at 37 degrees C. Control cultures were grown in medium alone while other cultures were supplemented with either testosterone alone at a concentration of 1 x 10(-7) M or with 10, 100, 500 ng LH plus testosterone, 10, 100, 500 ng FSH plus testosterone or 10, 100, 500 ng PRL plus testosterone. After 2 days of cultivation all cultures were terminated and media were frozen at 20 degrees C for further steroid analysis. Testosterone added to the culture medium in the absence of gonadotropins was without effect on estradiol and progesterone secretion by luteal cells collected in the corpora lutea of the early luteal phase. On the other hand testosterone added to the medium significantly increased progesterone and estradiol secretion by cultured luteal cells collected in the midluteal phase of the cycle. No additive stimulatory action of gonadotropins and testosterone on progesterone secretion was observed in cultures of luteal cells from the early luteal phase but this was not the case in cultures of luteal cells from the midluteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗