Androgen insensitivity and male infertility

A Gly684Ala substitution in the androgen receptor is the cause for azoospermia in a Chinese family with mild androgen insensitivity syndrome and normal hormone levels

Androgen receptor gene (AR) is essential for male growth and fertility. Its mutations are responsible for androgen insensitivity syndrome (AIS) that usually shows the phenotype of azoospermia resulting in male infertility. This study reported the first case of mild AIS with complete normal serum hormones in a Chinese family. The proband referred for infertility because of azoospermia. His uncle and two cousins are both infertile and have azoospermia. Whole-exome sequencing in the genetic analyses showed that the proband carries a novel hemizygous AR missense mutation, NM_000044.6: c.2051G>C (p.Gly684Ala), in exon four within the ligand-binding domain. His mother and maternal aunt are heterozygous carriers, while his father and brother are wildtype, indicating that the mutation in the proband was inherited from his mother. This pattern is consistent with the genetic model of the X-linked recessive inheritance of AR in AIS pathogenesis. HOPE predicts that p.Gly684Ala increases the hydrophobicity of AR but does not change the AR conformation. PolyPhen-2 predicts that p.Gly684Ala is harmful. This study provides the new knowledge to understand the AR gene mutations in MAIS.

Leydig and Sertoli cell function in individuals with genital ambiguity, 46,XY karyotype, palpable gonads and normal testosterone secretion: a case-control study

BACKGROUND

Because normal male sexual differentiation is more complex than normal female sexual differentiation, there are more cases of disorders of sex development (DSDs) with 46,XY karyotype that have unclear etiology. However, Leydig and Sertoli cell markers are rarely used in distinguishing such individuals.

OBJECTIVES

To evaluate the function of Leydig and Sertoli cells in individuals with genital ambiguity, 46,XY karyotype, palpable gonads and normal testosterone secretion.

STUDY DESIGN AND SETTING

Case-control study with 77 patients, including eight with partial androgen insensitivity syndrome, eight with 5α-reductase deficiency type 2 (5ARD2) and 19 with idiopathic 46,XY DSD, and 42 healthy controls, from the Interdisciplinary Study Group for Sex Determination and Differentiation (GIEDDS), at the State University of Campinas (UNICAMP), Campinas, Brazil.

METHODS

Baseline levels of gonadotropins, anti-Müllerian hormone (AMH), inhibin B, insulin-like 3 (INSL3), testosterone and dihydrotestosterone in cases, and AMH, inhibin B, and INSL3 levels in controls, were assessed.

RESULTS

There was no significant difference in age between cases and controls (P = 0.595). AMH and inhibin B levels were significantly lower in cases than in controls (P = 0.031 and P < 0.001, respectively). INSL3 levels were significantly higher in cases than in controls (P = 0.003). Inhibin B levels were lower in 5ARD2 patients (P = 0.045) and idiopathic patients (P = 0.001), in separate comparisons with the controls.

CONCLUSION

According to our findings, we can speculate that inhibin B levels may be used to differentiate among DSD cases.

Antioxidant-Based Therapies in Male Infertility: Do We Have Sufficient Evidence Supporting Their Effectiveness?

Under physiological conditions, reactive oxygen species (ROS) play pivotal roles in various processes of human spermatozoa. Indeed, semen requires the intervention of ROS to accomplish different stages of its maturation. However, ROS overproduction is a well-documented phenomenon occurring in the semen of infertile males, potentially causing permanent oxidative damages to a vast number of biological molecules (proteins, nucleic acids, polyunsaturated fatty acids of biological membrane lipids), negatively affecting the functionality and vitality of spermatozoa. ROS overproduction may concomitantly occur to the excess generation of reactive nitrogen species (RNS), leading to oxidative/nitrosative stress and frequently encountered in various human pathologies. Under different conditions of male infertility, very frequently accompanied by morpho-functional anomalies in the sperm analysis, several studies have provided evidence for clear biochemical signs of damages to biomolecules caused by oxidative/nitrosative stress. In the last decades, various studies aimed to verify whether antioxidant-based therapies may be beneficial to treat male infertility have been carried out. This review analyzed the results of the studies published during the last ten years on the administration of low-molecular-weight antioxidants to treat male infertility in order to establish whether there is a sufficient number of data to justify antioxidant administration to infertile males. An analysis of the literature showed that only 30 clinical studies tested the effects of the administration of low-molecular-weight antioxidants (administered as a single antioxidant or as a combination of different antioxidants with the addition of vitamins and/or micronutrients) to infertile males. Of these studies, only 33.3% included pregnancy and/or live birth rates as an outcome measure to determine the effects of the therapy. Of these studies, only 4 were case–control studies, and only 2 of them found improvement of the pregnancy rate in the group of antioxidant-treated patients. Additionally, of the 30 studies considered in this review, only 43.3% were case–control studies, 66.7% enrolled a number of patients higher than 40, and 40% carried out the administration of a single antioxidant. Therefore, it appears that further studies are needed to clearly define the usefulness of antioxidant-based therapies to treat male infertility.

Possible Protective Effects of Curcumin via Modulating of Androgen Receptor (AR) and Oct2 Gene Alterations in Cisplatin-Induced Testicular Toxicity in Rat

BACKGROUND

Cisplatin is a chemotherapeutic drug used to treat testicular cancer that induces testicular toxicity. This study aimed to investigate the possible role of androgens, androgen receptor, and organic cation transporter 2 (OCT2) in the protective effects of curcumin on cisplatininduced testicular toxicity.

METHODS

Thirty male Wistar rats were divided into five groups: 1- control (normal saline, 0.5 ml ip, daily for 10 consecutive days); 2- cisplatin (10 mg/kg ip, single dose at the first day); 3- cisplatin + curcumin (10 mg/kg ip, dissolved in 5% DMSO, daily for 10 consecutive days); 4- cisplatin + vehicle (DMSO 5%, 0.3 ml ip); and 5- curcumin (10 mg/kg ip). At the end of the study, a blood sample was obtained for testosterone measurement. The left testis was kept at -80. to measure androgen receptor (AR) and type 2 organic cation transporter (OCT2) gene expression and the right testis were kept in 10% formalin for histological analysis.

RESULTS

Cisplatin significantly decreased serum testosterone, declined testis AR gene expression, and increased OCT2 gene expression in testis (p<0.01). Curcumin treatment significantly prevented these alterations in testosterone and gene expressions (p<0.01). Moreover, curcumin significantly reversed the cisplatin-induced kidney tissue injury and increased spermatid and spermatozoa.

CONCLUSION

It is concluded that the ameliorative effect of curcumin in cisplatin-induced reproductive disorders was due to the modulation of testosterone and androgen receptors.

Long-term consequences of androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is one of the most common sexual developmental disorders. According to the grade of the remaining androgen receptor (AR) function, AIS is classified as complete (CAIS), partial (PAIS) or mild (MAIS). In CAIS, the prevalence of germ cell tumours is increased compared with the general population. Although patients with CAIS used to undergo gonadectomy before puberty, nowadays a gonadectomy is recommended after spontaneous puberty, and up to 15% of patients retain their gonads. Nevertheless, the risk of germ cell tumour increases gradually after puberty. Annual follow-up with ultrasound or magnetic resonance imaging (MRI) is recommended. Unfortunately, these imaging methods are not sensitive enough for the diagnosis of an in situ germ cell tumour. In PAIS, the risk of germ cell tumour is higher than in CAIS; therefore, an early gonadectomy or an orchidopexy is indicated. Optimal hormone replacement therapy (HRT) is necessary for long-term health. The risks of osteopenia and of regimen osteoporosis are higher, ESPECIALLY in patients with early gonadectomy. Infertility is the rule in CAIS and PAIS. A few mutations do not affect fertility detrimentally, and these are responsible for MAIS. In PAIS leading to a predominantly male phenotype or ambiguous genitalia, multiple surgical procedures for gynaecomastia and/or hypospadias are required. Some small studies have found a higher risk of obesity, hyperlipidaemia and impaired insulin sensitivity. Psychological support is essential, as the prevalence of psychiatric disorders is increased. In conclusion, the diagnosis of AIS has long-term consequences for which shared decision-making (physicians, patients, parents) is appropriate.

Cordycepin, an Active Constituent of Nutrient Powerhouse and Potential Medicinal Mushroom Cordyceps militaris Linn., Ameliorates Age-Related Testicular Dysfunction in Rats

Age-related male sexual dysfunction covers a wide variety of issues, together with spermatogenic and testicular impairment. In the present work, the effects of cordycepin (COR), an active constituent of a nutrient powerhouse Cordyceps militaris Linn, on senile testicular dysfunction in rats was investigated. The sperm kinematics, antioxidant enzymes, spermatogenic factors, sex hormone receptors, histone deacetylating sirtuin 1 (SIRT1), and autophagy-related mammalian target of rapamycin complex 1 (mTORC1) expression in aged rat testes were evaluated. Sprague Dawley rats were divided into young control (2-month-old; YC), aged control (12-month-old; AC), and aged plus COR-treated groups (5 (COR-5), 10 (COR-10), and 20 (COR-20) mg/kg). The AC group showed reduced sperm kinematics and altered testicular histomorphology compared with the YC group (p < 0.05). However, compared with the AC group, the COR-treated group exhibited improved sperm motility, progressiveness, and average path/straight line velocity (p < 0.05–0.01). Alterations in spermatogenesis-related protein and mRNA expression were significantly ameliorated (p < 0.05) in the COR-20 group compared with the AC group. The altered histone deacetylating SIRT1 and autophagy-related mTORC1 molecular expression in aged rats were restored in the COR-20 group (p < 0.05). In conclusion, the results suggest that COR holds immense nutritional potential and therapeutic value in ameliorating age-related male sexual dysfunctions.

Fertility Issues in Pediatric Urology

Improved understanding of the pathogenesis and natural history of many urologic disorders, as well as advances in fertility preservation techniques, has increased the awareness of and options for management of fertility threats in pediatric patients. In children, fertility may be altered by oncologic conditions, by differences in sexual differentiation, by gonadotoxic drugs and other side effects of treatment for nonurologic disorders, and by urologic conditions, such as varicocele and cryptorchidism. Although fertility concerns are best addressed in a multidisciplinary setting, pediatric urologists should be aware of the underlying pathophysiology and management options to properly counsel and advocate for patients.

Androgen insensitivity syndrome: a review

Androgenic insensitivity syndrome is the most common cause of disorders of sexual differentiation in 46,XY individuals. It results from alterations in the androgen receptor gene, leading to a frame of hormonal resistance, which may present clinically under 3 phenotypes: complete (CAIS), partial (PAIS) or mild (MAIS). The androgen receptor gene has 8 exons and 3 domains, and allelic variants in this gene occur in all domains and exons, regardless of phenotype, providing a poor genotype - phenotype correlation in this syndrome. Typically, laboratory diagnosis is made through elevated levels of LH and testosterone, with little or no virilization. Treatment depends on the phenotype and social sex of the individual. Open issues in the management of androgen insensitivity syndromes includes decisions on sex assignment, timing of gonadectomy, fertility, physcological outcomes and genetic counseling.

Fertility outcome and information on fertility issues in individuals with different forms of disorders of sex development: findings from the dsd-LIFE study

OBJECTIVE

To investigate fertility outcome in individuals with different forms of disorders of sex development (DSD), if assisted reproductive technology (ART) was used, and the patients' satisfaction with the information they had received.

DESIGN

A cross-sectional multicenter study, dsd-LIFE.

SETTING

Not applicable.

PATIENT(S)

A total of 1,040 patients aged ≥16 years with different DSD diagnoses participated.

INTERVENTION(S)

A web-based questionnaire was filled out by all participants. The participants could chose to take part in somatic investigations including ultrasonography.

MAIN OUTCOME MEASURE(S)

Information on partner, number of children, ART, adoption and step-children, general health, presence of gonads and uterus, current education and economic situation, received information on fertility issues, and satisfaction with the information, was collected.

RESULT(S)

In the total cohort, mean age 32 years, 33% lived with a partner, but only 14% reported having at least one child including 7% with ART, 4% adopted. Only 3.5% of the total cohort had been able to reproduce without ART, most frequently women with congenital adrenal hyperplasia, and only 0.7% of participants with other diagnoses. Of the participants, 72% had received information on fertility, but 17% were not satisfied with the information.

CONCLUSION(S)

Fertility outcome is significantly reduced in all types of DSD; however, fertility potential should be assessed individually. The satisfaction with how fertility problems have been discussed can be improved. The care of patients with DSD is complex, should be individualized, and new treatment possibilities incorporated. A close collaboration in multidisciplinary teams is therefore essential to improve the situation for individuals with DSD.

Fertility in disorders of sex development: A review

INTRODUCTION

Disorders of sex development (DSD) are a heterogeneous group of complex conditions that can affect chromosomal, gonadal, and/or phenotypical sex. In addition to impacts on internal and external genitalia,these conditions can affect fertility potentialto various degrees. In this review we discuss fertility issues including gonadalpreservation and reproductive outcomes based on specific DSD conditions.

METHODS AND MATERIALS

A systematic literature review was performed on Embase^™, PubMed^®, and Google Scholar^™ for disordersof sex development and infertility. Original research articles and relevant reviews were examinedand a synopsis of these data was generated for a comprehensive review of fertility potential in disorders of sex development.

RESULTS

While patients with some DSDs may have functioning gonads with viable germ cells but an inability to achieve natural fertility secondary to incongruent internal or external genitalia, other patients may have phenotypically normal genitalia but infertility due to abnormal gonad development. Fertility rates in females with congenital adrenal hyperplasia (CAH) depend on phenotype and are inversely proportionalto the severity of the disease. Men with classic CAH have reduced fertility and due to the presence of testicular adrenal rest tumors and to suppression of the hypothalamic-pituitary-gonadal axis by high systemic levels of androgens. Infertility is seen in complete androgen insensitivity and subfertility is common in partial cases. Fertility is rare in pure or mixed gonadal dysgenesis, ovotesticular disorder, Klinefelter syndrome, and XX males.

CONCLUSION

Fertility potential appears to be the highest in patientswith XX or XY CAH, especially non-classic forms. Advancements in assisted reproduction techniques has in rare cases produced offspring in some diagnoses thought to be universally infertile. Discussion of fertility issues with the patient and family is essential to the optimal treatment of each patient and an important part of the multi-disciplinary approach to evaluating and counseling these families.

Effects of ginseng on two main sex steroid hormone receptors: estrogen and androgen receptors

Ginseng has been used in China for at least two millennia and is now popular in over 35 countries. It is one of the world's popular herbs for complementary and alternative medicine and has been shown to have helpful effects on cognition and blood circulation, as well as anti-aging, anti-cancer, and anti-diabetic effects, among many others. The pharmacological activities of ginseng are dependent mainly on ginsenosides. Ginsenosides have a cholesterol-like four trans-ring steroid skeleton with a variety of sugar moieties. Nuclear receptors are one of the most important molecular targets of ginseng, and reports have shown that members of the nuclear receptor superfamily are regulated by a variety of ginsenosides. Here, we review the published literature on the effects of ginseng and its constituents on two main sex steroid hormone receptors: estrogen and androgen receptors. Furthermore, we discuss applications for sex steroid hormone receptor modulation and their therapeutic efficacy.

Up-regulation of SOX9 in sertoli cells from testiculopathic patients accounts for increasing anti-mullerian hormone expression via impaired androgen receptor signaling

Background

Testosterone provokes Sertoli cell maturation and represses AMH production. In adult patients with Sertoli-cells-only syndrome (SCOS) and androgen insensitivity syndrome (AIS), high level of AMH expression is detected in Sertoli cells due to defect of androgen/AR signaling.

Objective

We postulated that up-regulation of SOX9 due to impairment of androgen/AR signaling in Sertoli cells might explain why high level of anti-Mullerian hormone (AMH) expression occur in these testiculopathic patients.

Methods

Biological research of testicular specimens from men with azoospermia or mouse. The serum hormone levels were studied in 23 men with obstructive azoospermia, 33 men with SCOS azoospermia and 21 volunteers with normal seminograms during a period of 4 years.

Immunohistochemical staining and reverse-transcription PCR were used to examine the relationships among AR, SOX9 and AMH expression in adult human and mouse testes. The ability of AR to repress the expression of SOX9 and AMH was evaluated in vitro in TM4 Sertoli cells and C3H10T1/2 cells.

Results

SCOS specimens showed up-regulation of SOX9 and AMH proteins but down-regulation of AR proteins in Sertoli cells. The mRNA levels of AR were significantly lower and the SOX9, AMH mRNA levels higher in all SCOS patients compared to controls (P< 0.05). The testosterone levels in the SCOS patients were within the normal range, but most were below the median of the controls. Furthermore, our invitro cell line experiments demonstrated that androgen/AR signaling suppressed the gene and protein levels of AMH via repression of SOX9.

Conclusions

Our data show that the functional androgen/AR signaling to repress SOX9 and AMH expression is essential for Sertoli cell maturation. Impairment of androgen/AR signaling promotes SOX9-mediated AMH production, accounts for impairments of Sertoli cells in SCOS azoospermic patients.

Effect of methanol extract of Basella alba L. (Basellaceae) on the fecundity and testosterone level in male rats exposed to flutamide in utero

We evaluated the effect of the methanol extract of Basella alba (MEBa) on testosterone level and fecundity/fertility in male rats exposed in utero to flutamide - an androgen receptor antagonist. For this purpose, 1.5- and 2.5 -month-old male rats exposed in utero to flutamide were treated with the MEBa (1 mg kg(-1) ) for 2 and 1 month respectively. Five days before the end of treatment, rats were housed with females to assess their fecundity/fertility. Thereafter, rats were sacrificed and blood collected for the quantification of testosterone. Flutamide-exposed male rats showed a decrease in their ano-genital distance (AGD, P < 0.05) and were infertile. In normal (methylcellulose-exposed) animals, MEBa provoked an increase in testosterone level in 1.5- (P < 0.008) and 2.5 -month-old rats (P < 0.01) concomitantly with the improvement in their fecundity by 25%. In flutamide-exposed male rats, MEBa increased testosterone level in 1.5 -month-old rats (P < 0.001) without any effect on their fecundity; while in 2.5- month-old rats, MEBa did not affect the testosterone level but improved fecundity (by 25%) and fertility (P < 0.001). This study demonstrated the positive effect of MEBa to enhance fecundity/fertility in normal male rats and in rats exposed to the antiandrogen flutamide during their foetal life.

Androgens and spermatogenesis: lessons from transgenic mouse models

Transgenic mouse models have contributed considerably to our understanding of the cellular and molecular mechanisms by which androgens control spermatogenesis. Cell-selective ablation of the androgen receptor (AR) in Sertoli cells (SC) results in a complete block in meiosis and unambiguously identifies the SC as the main cellular mediator of the effects of androgens on spermatogenesis. This conclusion is corroborated by similar knockouts in other potential testicular target cells. Mutations resulting in diminished expression of the AR or in alleles with increased length of the CAG repeat mimick specific human forms of disturbed fertility that are not accompanied by defects in male sexual development. Transcriptional profiling studies in mice with cell-selective and general knockouts of the AR, searching for androgen-regulated genes relevant to the control of spermatogenesis, have identified many candidate target genes. However, with the exception of Rhox5, the identified subsets of genes show little overlap. Genes related to tubular restructuring, cell junction dynamics, the cytoskeleton, solute transportation and vitamin A metabolism are prominently present. Further research will be needed to decide which of these genes are physiologically relevant and to identify genes that can be used as diagnostic tools or targets to modulate the effects of androgens in spermatogenesis.

Male infertility and the involvement of the X chromosome

BACKGROUND

Male infertility is a worldwide problem, keeping many researchers puzzled. Besides environmental factors, much attention is paid to single gene defects. In this view, the sex chromosomes are particularly interesting since men only have a single copy of these chromosomes. The involvement of the Y chromosome in male infertility is obvious since the detection of Yq microdeletions. The role of the X chromosome, however, remains less understood.

METHODS

Articles were obtained by searching PubMed until December 2008. A first search attempted to identify genes located on the X chromosome potentially important for spermatogenesis. A second part of the study was focused on those genes for which the role has already been studied in infertile patients.

RESULTS

Multiple genes located on the X chromosome are expressed in testicular tissues. The function of many genes, especially the cancer-testis genes, has not been studied so far. There were striking differences between mouse and human genes. In the second part of the study, the results of mutation analyses of seven genes (AR, SOX3, USP26, NXF2, TAF7L, FATE and AKAP4) are described. Except for AR, no infertility causing mutations have, thus far, been described. It cannot be excluded that some of the observed changes should be considered as risk factors for impaired spermatogenesis.

CONCLUSIONS

It can be concluded that, so far, the mutation analysis of X-linked genes in humans, presumed to be crucial for spermatogenesis or sperm quality, has been disappointing. Other approaches to learn more about male infertility are necessary.

Gender role behavior in children with XY karyotype and disorders of sex development

Children exhibit gender-typical preferences in play, toys, activities and interests, and playmates. Several studies suggest that high concentrations of pre- and postnatal androgens contribute to male-typical behavior development, whereas female-typical behavior develops in the absence of high androgens levels. This study aims to explore the consequences of hypoandrogenization on gender-typical behavior in children who have an XY karyotype and disorder of sex development (DSD). Participants included 33 children (ages 2-12 years) with an XY karyotype and DSD; 21 reared as girls and 12 reared as boys. Children's preferred activities and interests and playmate preferences were assessed with parent report questionnaires, a structured free-play task, and choice of a toy to keep as a gift. Participant's responses were compared to those of children recruited in a pre-school and elementary school survey (N=166). In this study, the degree of hypoandrogenization as indicated by genital stage and diagnosis showed a significant relationship to nearly all of the gender-related behaviors assessed, supporting the hypothesis that masculinization of gender role behavior is a function of prenatal androgen exposure. Despite the fact that children with partial androgen effects reared as girls showed increased "boyish" behaviors, they did not show increased signs of gender identity confusion or instability on a group level. We conclude that androgen exposure plays a decisive role in the development of gender-typical behavior in children with XY karyotype and DSD conditions.

Male infertility and androgen receptor gene mutations: clinical features and identification of seven novel mutations

OBJECTIVE

Androgens and a functioning androgen receptor (AR) are essential for development and maintenance of the male phenotype and spermatogenesis. Consistent with this, mutations in the AR gene cause a variety of defects related to androgen insensitivity, ranging from complete feminization to phenotypic males with infertility. The aim of his study was to analyse the prevalence of AR gene mutations in male infertility and to clarify the genotype-phenotype relation.

DESIGN

Males with infertility were recruited consecutively at the Centre for Male Gamete Cryopreservation at the University of Padova from January 1996 to January 2005.

PATIENTS

One thousand five hundred and seventeen men with < 10 million sperm/ml and 310 age-matched normozoospermic controls.

METHODS

Screening for AR gene mutation was done by DHPLC and sequencing, and reproductive hormone concentrations were measured.

RESULTS

We found 20 mutations in 26 of 1517 patients (1.7%) and no mutations in controls. A high number of mutations localized in exon 1 of the AR gene coding for the transactivation domain of the protein. Of 20 mutations, 7 represent novel mutations. With respect to men without AR mutations, subjects with AR mutations have lower ejaculate volume, higher testosterone levels, higher oestradiol levels, and higher androgen sensitivity index. However, the ranges for these variables were highly overlapping between men with and without AR gene mutations. Also clinical manifestations of AR mutations are not unique and 22 men had only spermatogenic impairment.

CONCLUSIONS

AR gene mutations are quite frequent in unselected infertile men but no specific hormonal or clinical data could be used to preselect patients at risk of mutations.

CAG repeat length in an infertile male population of Irish origin

The androgen receptor (AR) gene, located on the X chromosome, is an important regulator of human spermatogenesis. In the past decade, the link between the CAG polyglutamine tract, situated on exon one of the AR gene, and reduced spermatogenesis has become a controversial one. Alterations in the length of the CAG polyglutamine tract have been associated with prostate cancer at a reduced intrinsic length and neuromuscular diseases at a CAG repeat length of > or = 40. Minimal intermediate increases have been linked with depressed spermatogenesis in infertile males. Asian and Australian groups have published an association between increased CAG repeat length and reduced spermatogenesis while many European studies have found no such association. The aim of this study was to document the association between increased CAG repeat length and reduced spermatogenesis in a group of Irish infertile males and controls known to have fathered at least one child. The study employed the ABI 377 DNA sequencer to size the CAG repeat region of exon one of the AR gene in each group. Statistical analysis revealed no actual link between the length of the CAG tract and a reduction of spermatogenesis in a cohort of infertile patients (n = 66) of Irish ethnic origin when compared to a fertile control group (n = 77) (p = 0.599).

Molecular pathology of the androgen receptor in male (in)fertility

Idiopathic male infertility, accounting for 40% of all male infertility cases, is postulated to have a genetic basis. The androgen receptor (AR) plays a crucial post-meiotic role during male germ cell differentiation, which includes terminal differentiation of spermatids and their release from the seminiferous epithelium. Mutations in the AR gene result in a condition known as androgen insensitivity syndrome (AIS) affecting normal male morphogenesis. Depending on the severity of the syndrome, the external phenotype can range from normal female to normal male. In almost all cases affected individuals are infertile. In seven reported cases individuals appeared to suffer primarily or solely from male infertility, suggesting these AR mutations specifically cause male infertility. Three of these mutations are possibly population specific. Longer CAG repeats present in exon 1 of the AR have been studied as a possible risk factor for male infertility. Results are contradictory, with a trend to significance (Asian populations) and non-significance (European populations). Recent advances in protein modelling techniques may result in a much better understanding of the mechanism of action of the known infertility mutations. The determination of the significance of longer CAG repeats is likely to require studies that examine CAG repeat lengths in spermatozoa as well as patients' blood.

Testosterone metabolism, dose-response relationships and receptor polymorphisms: selected pharmacological/toxicological considerations on benefits versus risks of testosterone therapy in men

In this review selected toxicological problems related to testosterone therapy in hypogonadal men are discussed. Applying "classical" pharmacological/toxicological findings (e.g. animal studies on short- and long-term toxicity) to clinical situations is not very helpful. Molecular biological knowledge and especially evaluation of epidemiological studies, as well as intervention studies, on testosterone therapy in hypogonadal men are more useful. Potential risks include overdosage for lifestyle reasons, e.g. excessive muscle building and reduction of visceral obesity, when erythrocytosis occurs concomitantly. Modern galenic formulations of testosterone administration (e.g. transdermal gel, suitable testosterone esters for intramuscular application and newer oral preparations) avoid supraphysiological serum concentrations, therefore significantly reducing the toxicological risk. A hypothetical model of the toxicological risks of testosterone therapy is given that is based on the influence of testosterone metabolism (aromatization vs. reduction) of the respective parameter/target chosen. Finally, the great influence of polymorphisms of the androgen receptor on the assessment of toxicological risk and on the individualization of androgen therapy is shown. Already existing national, continental and international guidelines or recommendations for the testosterone therapy should be harmonized.