Induction of male sexual behavior in the rat by 7 alpha-methyl-19-nortestosterone, an androgen that does not undergo 5 alpha-reduction

Androgen receptors and sociosexual behaviors in mammals: The limits of generalization

Circulating testosterone is easily aromatized to estradiol and reduced to dihydrotestosterone in target tissues and elsewhere in the body. Thus, the actions of testosterone can be mediated either by the estrogen receptors, the androgen receptor or by simultaneous action at both receptors. To determine the role of androgens acting at the androgen receptor, we need to eliminate actions at the estrogen receptors. Alternatively, actions at the androgen receptor itself can be eliminated. In the present review, I will analyze the specific role of androgen receptors in male and female sexual behavior as well as in aggression. Some comments about androgen receptors and social recognition are also made. It will be shown that there are important differences between species, even between strains within a species, concerning the actions of the androgen receptor on the behaviors mentioned. This fact makes generalizations from one species to another or from one strain to another very risky. The existence of important species differences is often ignored, leading to many misunderstandings and much confusion.

Hormone-dependent medial preoptic/lumbar spinal cord/autonomic coordination supporting male sexual behaviors

Testosterone (T) can act directly through neural androgen receptors (AR) to facilitate male sexual behavior; however, T's metabolites also can play complicated and interesting roles in the control of mating. One metabolite, dihydrotestosterone (DHT) binds to AR with significantly greater affinity than that of T. Is that important behaviorally? Another metabolite, estradiol (E), offers a potential alternative route of facilitating male mating behavior by acting through estradiol receptors (ER). In this review we explore the roles and relative importance of T as well as E and DHT at various levels of the neuroaxis for the activation of male sex behavior in common laboratory animals and, when relevant research findings are available, in man.

Comparison of 7α-methyl-19-nortestosterone effectiveness alone or combined with progestins on androgen receptor mediated-transactivation

7α-methyl-19-nortestosterone (MENT) is an androgen with potent gonadotropin inhibitory activity and prostate-sparing effects. These attributes give MENT advantages over testosterone as a male contraceptive, but, as in the case of testosterone, a partial dose-dependent suppression of spermatogenesis has been observed. Combination of testosterone or MENT with synthetic progestins improves the rate of azoospermia; however, it is unknown whether these combinations affect hormone androgenicity or exert synergistic effects via progestational or androgenic interaction. Herein, using transactivation assays, we examined the ability of MENT alone or combined with several 19-nor-derived synthetic progestins to activate androgen receptor (AR)-dependent gene transcription. In addition, the capability of 7α-methyl-estradiol (7α-methyl-E2), an aromatized metabolite of MENT, to transactivate gene transcription via estrogen receptor α (ERα; ESR1) or ERβ (ESR2) was also investigated. As expected, MENT induced gene transactivation through either the progesterone receptor (PGR) or the AR. MENT was as efficient as progesterone in activating PGR-mediated reporter gene expression, but it was ten times more potent than testosterone and dihydrotestoterone in activating of AR-driven gene expression. The addition of increasing concentrations of other 19-nortestosterone derivatives (norethisterone or levonorgestrel) did not affect, in a significant manner, the ability of MENT to activate AR-dependent reporter gene transcription. The same results were obtained with different cell lines. 7α-Methyl-E2 resulted in potent estrogen activity via both ER subtypes with efficiency similar to natural E2. These results suggest that the addition of 19-nortestosterone-derived progestins, as a hormonal adjuvant in male fertility strategies for effective spermatogenic suppression, does not display any detrimental effect that would interfere with MENT androgenic transcriptional activity.

Testostérone et contrôle central de l’érection

La testostérone orchestre l’organisation périnatale et l’activation adulte des structures nerveuses cérébrales et spinales impliquées dans l’expression du comportement sexuel mâle. Cette revue décrit brièvement les différents effets de la testostérone dans la régulation de la motivation sexuelle et de l’érection, et les modèles génétiques générés, jusqu’à présent, dans le but d’élucider ses mécanismes d’action centraux.

Protective actions of sex steroid hormones in Alzheimer's disease

Risk for Alzheimer's disease (AD) is associated with age-related loss of sex steroid hormones in both women and men. In post-menopausal women, the precipitous depletion of estrogens and progestogens is hypothesized to increase susceptibility to AD pathogenesis, a concept largely supported by epidemiological evidence but refuted by some clinical findings. Experimental evidence suggests that estrogens have numerous neuroprotective actions relevant to prevention of AD, in particular promotion of neuron viability and reduction of beta-amyloid accumulation, a critical factor in the initiation and progression of AD. Recent findings suggest neural responsiveness to estrogen can diminish with age, reducing neuroprotective actions of estrogen and, consequently, potentially limiting the utility of hormone therapies in aged women. In addition, estrogen neuroprotective actions are also modulated by progestogens. Specifically, continuous progestogen exposure is associated with inhibition of estrogen actions whereas cyclic delivery of progestogens may enhance neural benefits of estrogen. In recent years, emerging literature has begun to elucidate a parallel relationship of sex steroid hormones and AD risk in men. Normal age-related testosterone loss in men is associated with increased risk to several diseases including AD. Like estrogen, testosterone has been established as an endogenous neuroprotective factor that not only increases neuronal resilience against AD-related insults, but also reduces beta-amyloid accumulation. Androgen neuroprotective effects are mediated both directly by activation of androgen pathways and indirectly by aromatization to estradiol and initiation of protective estrogen signaling mechanisms. The successful use of hormone therapies in aging men and women to delay, prevent, and or treat AD will require additional research to optimize key parameters of hormone therapy and may benefit from the continuing development of selective estrogen and androgen receptor modulators.

Structural characteristics of anabolic androgenic steroids contributing to binding to the androgen receptor and to their anabolic and androgenic activities. Applied modifications in the steroidal structure

Anabolic androgenic steroids (AAS) are synthetic derivatives of testosterone introduced for therapeutic purposes providing enhanced anabolic potency with reduced androgenic effects. Androgens mediate their action through their binding to the androgen receptor (AR) which is mainly expressed in androgen target tissues, such as the prostate, skeletal muscle, liver and central nervous system. This paper reviews some of the wide spectrum of testosterone and synthetic AAS structure modifications related to the intended enhancement in anabolic activity. The structural features of steroids necessary for effective binding to the AR and those which contribute to the stipulation of the androgenic and anabolic activities are also presented.

Sexual dysfunction in men and women with endocrine disorders

Endocrine disease frequently interrupts sexual function, and sexual dysfunction may signal serious endocrine disease. Diabetic autonomic neuropathy and endothelial dysfunction impair erectile function, and phosphodiesterase inhibition produces only moderate benefit. The effect of diabetes on women's sexual function is complex: the most consistent finding is a correlation between sexual dysfunction and depression. Reductions in testosterone level in men are associated with low sexual desire and reduced nocturnal erections and ejaculate volume, all of which improve with testosterone supplementation. The age-dependent decline in testosterone production in men is not associated with precise sexual symptoms, and supplementation has not been shown to produce sexual benefit. In women, sexual dysfunction has not been associated with serum testosterone, but this may be confounded by limitations of assays at low concentrations and by the greater importance of intracellular production of testosterone in women than in men. Testosterone supplementation after menopause does improve some aspects of sexual function in women, but long-term outcome data are needed. More research on the sexual effects of abnormal adrenal and thyroid function, hyperprolactinaemia, and metabolic syndrome should also be prioritised. We have good data on local management of the genital consequences of oestrogen lack, but need to better understand the potential role of systemic oestrogen supplementation from menopause onwards in sexually symptomatic women.

Comparison of the growth-promoting effects of testosterone and 7-alpha-methyl-19-nor-testosterone (MENT) on the prostate and levator ani muscle of LPB-tag transgenic mice

BACKGROUND

7-alpha-methyl-19-nortestosterone (MENT) is being considered for androgen replacement in testosterone deficient men and as a male contraceptive. Because androgenic effects on the prostate are a major concern, we have evaluated MENT in a transgenic model of prostate cancer.

METHODS

LPB-Tag mice were castrated and infused with testosterone (T; 5 or 30 microg/day) or MENT (5 or 30 microg/day) for 4 weeks. Prostate, seminal vesicle, and levator ani muscle (LAM) weights were compared.

RESULTS

At an equivalent dose, MENT maintained or stimulated the mean weights of these organs more than T. However, the dorsolateral prostate/LAM ratio of weights did not favor MENT, but DNA/mg tissue and Ki 67 immunostaining suggested that MENT may increase DNA less than T.

CONCLUSIONS

MENT is more potent than T in maintaining or stimulating prostate, seminal vesicle, and LAM. Using doses that resulted in comparable stimulation of the levator ani muscle, MENT had similar effect on prostate weight, but increased DNA/mg prostate less than T in this transgenic mouse model of prostate cancer.

Pharmacological developments in male contraception

To date, the current methods of male contraception are limited to condoms, coitus interruptus and vasectomy, all of which are beset with difficulties. The condom is inconvenient, dulls sensation, and although somewhat effective against sexually transmitted disease, has an increased failure rate over time of usage. Coitus interruptus reduces the pleasurable aspects of intercourse and is plagued with a high failure rate. Vasectomy is virtually sterilisation. The current research into new forms of contraception is as diverse as the mechanisms controlling male fertility. The majority of effort has focused on antispermatogenic agents. Hormonal agents that suppress spermatogenesis appear nearest to final development and are primarily centred around various testosterone esters. These can be administered alone or in combination with progestogens. Another promising line of study centres on gonadotropin releasing hormone (GnRH) antagonism resulting in suppression of gonadotropins. Non-hormonal antispermatogenic agents include numerous phytochemicals, and testicular enzyme inhibitors. Post-testicular approaches to male contraception include agents that interfere with sperm metabolism, motility, maturation or transport. This review summarises recent clinical and animal studies on these compounds with emphasis on their mechanism of action, advantages and drawbacks.

Hormone-like behavioral effects of levonorgestrel and its metabolites in the male rat

Levonorgestrel (LNG), a contraceptive progestin, exhibits, besides its progestational activity, other hormone-like effects at the peripheral level. To assess whether LNG and its metabolites exert androgenic and/or estrogenic actions at the central nervous system (CNS), their effects on male sexual behavior in castrated rats were examined. LNG, 5alpha-dihydro LNG (5alphaLNG), and the 3alpha,5alpha- and 3beta,5alpha-tetrahydro derivatives of LNG (3alphaLNG and 3betaLNG, respectively) were administered for 3 weeks either alone (1000 microg/day) or in combination (300 microg/day) with 5alpha-dihydrotestosterone (DHT, 300 microg/day) or with estradiol-17beta (E(2), 5 microg/day). Copulatory behavior was assessed twice per week and sex accessory organs weights recorded at the end of treatments. LNG restored full copulatory behavior comparable to that of testosterone treated animals, although with a slight delay, whereas 5alphaLNG induced male sexual behavior in a significantly lower number of subjects. 3betaLNG and 3alphaLNG induced mounting but failed to restore intromission and ejaculation. Combined LNG+E(2) treatment fully activated mounting and intromission, but ejaculation was only partially restored. Combined 5alphaLNG+E(2) treatment and the combinations of 3alphaLNG or 3betaLNG with E(2) were significantly less effective, activating fewer intromissions and ejaculations. 3alphaLNG and 5alphaLNG, in combination with DHT, restored male sexual behavior. LNG, but not its metabolites, induced a significant increase on the weight of sex accessory organs. The overall results demonstrated that high doses of LNG induce a potent androgen agonistic behavioral effect and that its A-ring reduction diminishes this potency and enables a shift towards a weak estrogen-like effect.

7Alpha-methyl-19-nortestosterone maintains sexual behavior and mood in hypogonadal men

The synthetic steroid 7alpha-methyl-19-nortestosterone (MENT) is a potent androgen that is resistant to 5alpha-reductase. It thus has decreased activity at the prostate and may have advantages over testosterone-based regimens in long term treatment or as part of a male contraceptive. Administration to eugonadal men results in suppression of gonadotropins, but its ability to support androgen-dependent behavior has not been investigated. For sustained release administration, MENT acetate was used, because its diffusion characteristics were more suitable for use in implants. However, upon release the acetate is rapidly hydrolyzed, and MENT is the biologically active moiety in circulation. We studied the effects of MENT on sexual interest and activity, spontaneous erection, and mood states in comparison with testosterone enanthate (TE) in 20 Caucasian and Chinese hypogonadal men recruited in Edinburgh and Hong Kong (n = 10 in each center). Outcomes were measured using a combination of daily diaries, semistructured interviews, and questionnaires. Nocturnal penile tumescence (NPT) was also recorded in the Edinburgh group. After withdrawal of androgen replacement treatment (wash-out phase) for a minimum of 6 weeks, subjects were randomized to two groups in a cross-over design. Drug treatment regimens were of 6-week duration and consisted of two implants, each containing 115 mg MENT acetate, inserted s.c. into the upper arm and removed after 6 weeks and two injections of TE (200 mg, i.m.) 3 weeks apart. MENT treatment resulted in stable plasma MENT concentrations of 1.4 +/- 0.1 nmol/L after 3 weeks and 1.3 +/- 0.1 nmol/L after 6 weeks (mean +/- SEM; all men). Nadir testosterone concentrations were 3.6 +/- 0.6 nmol/L at the end of the wash-out phase and 9.4 +/- 0.6 nmol/L 3 weeks after each injection. There were no differences in hormone concentrations between centers. There were no adverse toxicological effects. There were only minor differences between the two treatments. Both MENT and TE treatment resulted in significant increases in sexual interest and activity, spontaneous erection (both by self-report and NPT measurement), and increases in positive moods, with decreases in negative moods in the Edinburgh group. In the Hong Kong group, both treatments increased waking erection, with a trend toward increased sexual interest and activity. Mood states appeared to be less affected during the wash-out phase than in Edinburgh men and showed no significant response to either treatment. These results demonstrate that MENT has similar effects on sexual activity and mood states as testosterone in hypogonadal men. As NPT is a physiological androgen-dependant outcome, these data provide further evidence for the androgenicity of MENT. The lack of detected effect of either androgen in Hong Kong men other than on waking erection illustrates the importance of the cultural context of symptomatology and its measurement. The appropriate dose of MENT remains to be determined, but these results support its development as a potential androgen replacement therapy.

Testosterone stimulation of the medial preoptic area and medial amygdala in the control of male hamster sexual behavior: redundancy without amplification

Receptors for gonadal steroids are present in an interconnected network of limbic nuclei. The existence of this network structure has important implications for how steroids control reproductive physiology and behavior. In 1986, Cottingham and Pfaff proposed that properties of a steroid-responsive neural network could include redundancy, amplification, stability and selective filtering. The present study tested the concept of steroid amplification, using male hamster sexual behavior as a model. In the male hamster, the medial amygdaloid nucleus (Me) and medial preoptic area (MPOA) are essential for mating behavior, and both nuclei transduce steroid cues to facilitate copulation. To determine if steroid action at multiple interconnected nuclei amplifies mating, the present study compared sexual behavior in castrated male hamsters bearing unilateral intracranial implants of testosterone in Me or MPOA with that of males with dual testosterone implants in Me and MPOA. Implants that stimulated androgen receptor-containing neurons in Me or MPOA stimulated copulatory behavior above castrate levels. However, behavior of males with dual implants was not significantly different from that of males with single implants. This suggests that steroid action at either MPOA or Me is sufficient to facilitate mating, but dual stimulation of these reciprocally-connected nuclei does not amplify sexual behavior.

Estrogenic and progestational activity of 7alpha-methyl-19-nortestosterone, a synthetic androgen

Synthetic androgens exhibit estrogenic/antiestrogenic and progestational activities in addition to their androgenic effects. To investigate the pharmacological action of the synthetic androgen, 7alpha-methyl-19-nortestosterone (MENT), we examined its action in female rodents. The criteria employed for estrogenic/antiestrogenic effects were, uterine weight increase, vaginal cornification, induction of progesterone receptors (PR) synthesis and stimulation of peroxidase activity in the uteri of ovariectomized rats and mice. MENT increased uterine weight in a dose dependent manner, but did not cause vaginal cornification or stimulate PR synthesis in the uterus. The uterotropic activity of MENT was 200-fold lower than that of estradiol. Estrogen receptor (ER) bound [3H]-E2 was displaced by E2 and MENT with ED50 values of 70 pg and 250 ng, respectively, a 3,500 fold difference in their binding affinity. The low binding of MENT to ER, in contrast to its relatively high uterotropic action, suggested that receptors other than ER may be involved in its action on the uterus. The progestational activity of MENT in immature rabbits using the McPhail index assay was comparable to that of progesterone. Binding affinities of MENT and progesterone to PR were also comparable. However, the action of MENT on the uterus does not seem to be a progestational effect since mifepristone, an antiprogestin, had no effect on MENT-induced uterine growth. Specific androgen receptors (AR) in uterine cytosol were demonstrated. The involvement of AR in MENT action was confirmed by using an antiandrogen (flutamide) and an antiestrogen (ICI-182) in ovariectomized mice. Although MENT did not block the uterotropic effect of E2, it inhibited the E2-induced cornification of vaginal epithelium, induction of uterine PR synthesis and increase in uterine peroxidase activity in ovariectomized rats. The antiestrogenic effect of MENT was also blocked by flutamide. These results suggest that the uterotropic and antiestrogenic effects of androgens are mediated via AR. It is concluded that the increase in uterine weight caused by MENT is attributable to its anabolic effects.

Androgens and male sexual behavior from mice to men

Exogenous androgenic hormones or drugs that affect endogenous androgen levels are now used in a variety of human applications [cf. Bardin et al. (1991)]. Therefore, an increasing number of well-controlled physiological, clinical, and psychological studies have examined the effects of androgens on muscle, prostate, lipids, and bone, as well as the cardiovascular, immune, and nervous systems. The increasing number of androgens and delivery systems that are currently available or under development should also increase the prevalence of androgen therapy (Table 1). As androgen use increases, a crucial area of research is the effect of androgens on sexual behavior, which encompasses sexual desire, motivation, performance, and satisfaction. There is a large body of animal data documenting hormonal regulation of male sexual behavior and the neural sites of action of these hormones. Clinical data on the effects of androgens on human male sexuality come from correlative studies of endogenous testosterone levels and sexual function, treatment of men who are testosterone deficient, and men using hormonal contraceptives.

Male pseudohermaphroditism due to primary 5 alpha-reductase deficiency: variation in gender identity reversal in seven Mexican patients from five different pedigrees

In the present study, we describe the clinical, endocrinological, psychosexual and biochemical features of 7 Mexican male pseudohermaphrodites with primary 5 alpha-reductase deficiency in whom heterogeneity in the pattern of gender identity change at puberty was observed. The patients belonged to 5 different pedigrees from diverse locations in Mexico. Six of them were admitted to the Hospital during or after puberty. The one prepubertal subject was the sibling of a previously studied patient. Basal serum gonadotropins were determined by double antibody radioimmunoassay. Basal and choriogonadotropin (CG)-stimulated concentrations of androstenedione (A), testosterone (T) and dihydrotestosterone (DHT) were determined by radioimmunoassay after extraction and separation by celite chromatography. Urinary aetiocholanolone, androsterone and C19 and C21 5 beta/5 alpha metabolite ratios were analyzed by capillary gas chromatography. Enzyme activity and androgen receptors were studied in fibroblasts cultured from genital skin. Psychological assessment was performed using the Bender-Gestalt Wechsler Adult Intelligence Scale, the Rorschach Ink Blot and the Thematic Apperception Tests. All 7 patients were unambiguously reared as females; three spontaneously changed their gender identity and role from female to male after puberty, another one changed during psychotherapy at the end of puberty. Two patients (one prepubertal and the other pubertal) have been under therapy during 1.5 years, but due to familial and social factors a female gender has prevailed. The remaining patient consulted at age 15 because of virilization; her female gender identity did not change after more than one year of treatment and due to the fact she was depressed and had suicidal tendencies, the penis and testes were removed.(ABSTRACT TRUNCATED AT 250 WORDS)

Aromatization of 7 alpha-methyl-19-nortestosterone by human placental microsomes in vitro

Part of the biological effects of testosterone (T) are mediated by its enzymatic reduction to 5 alpha-dihydrotestosterone (DHT) or aromatization to estradiol (E2). 7 alpha-Methyl-19-nortestosterone (MENT) is a synthetic androgen that is considerably more potent than T. Previous studies have shown that MENT is not 5 alpha-reduced. The studies reported here were undertaken to determine whether MENT undergoes enzymatic aromatization in vitro. Human placental microsomes were used as the source of the aromatase. Radioactive or nonradioactive T or MENT was incubated with the microsomes in the presence of NADPH and the metabolites extracted out with ethyl ether. Following evaporation of ether, the residue was dissolved in benzene-petroleum ether and extracted with 0.4 N NaOH which selectively removes phenolic metabolites of the androgens. When either radioactive T or MENT was incubated with the aromatase in the presence of NADPH, there was a 20-fold increase in the amount of radioactivity extracted with NaOH. In contrast, if the incubation was carried out in the absence of NADPH or in the presence of R76713, an aromatase inhibitor, most of the radioactivity remained in the benzene-petroleum ether phase. To further identify the enzymatic reaction products, thin layer chromatography (TLC) was performed. The Rf value for MENT was 0.22 while that of the major reaction product was 0.34, which corresponded with the RF value of the estrogen, 7 alpha-methyl-estradiol (MeE2). This was further verified by using a second solvent system for the chromatographic separation. In an effort to ascertain whether the metabolites bind to estrogen receptors (ER), rat uterine cytosol was used. NaOH extracts of medium following incubation of nonradioactive MENT with microsomes showed competitive inhibition of [3H]E2 binding to rat uterine ER. Furthermore, after [3H]MENT was incubated with microsomes, the radioactive metabolite extracted in NaOH showed specific binding to the ER which could readily be displaced with E2 or MeE2. These results indicate that like T, MENT undergoes enzymatic aromatization.