High prevalence of hypogonadism and associated impaired metabolic and bone mineral status in subfertile men.

OBJECTIVE: It is yet unknown to which degree young subfertile men present with signs of hypogonadism and whether low testosterone concentration, like in older men, is associated with risk of osteoporosis and metabolic derangements in those subjects. The objective was therefore to investigate the prevalence of hypogonadism and its association with metabolic and bone parameters in young subfertile men. DESIGN: Cross-sectional case-control study. PATIENTS: Men from infertile couples (n = 192); 18-50 years; sperm concentration <20 × 10(6) /ml and population-based age-matched controls (n = 199). MEASUREMENTS: Blood sampling, anthropometrics, blood pressure, ankle-brachial index and assessment by dual-energy X-ray absorptiometry were undertaken. Odds ratios of biochemical hypogonadism (total testosterone <8·0 nmol/l and/or luteinizing hormone ≥8·6 IU/l and/or ongoing androgen replacement therapy) were calculated. Serum concentrations of sex hormones, lipids, glucose, insulin and HbA1c were assessed and bone mineral density (BMD) evaluated. RESULTS: Compared to controls, the risk of hypogonadism was increased among subfertile men (OR 10; 95% CI, 5·1, 22), being highest in those with nonobstructive azoospermia. Hypogonadal men had higher HbA1c concentration (mean diff. 2·8 mmol/mol; 95% CI, 0·64, 4·9; P = 0·011) and lower lumbar spine BMD (mean diff. 0·05 g/cm(2) ; 95% CI, 0·01, 0·10; P = 0·032) compared to eugonadal subfertile men, even more pronounced in subfertile men with subnormal testosterone levels. CONCLUSION: Young subfertile men have 10 times increased OR of hypogonadism, which is linked to increased HbA1c and decreased bone mineralization. Endocrine assessment and, if needed, measures to prevent metabolic sequelae and osteoporosis should be included in the routine management of men from infertile couples.

Serum miR-155 as a potential biomarker of male fertility.

STUDY QUESTION: Are serum levels of micro-RNAs miR-155 and miR-146a associated with male fertility, low-grade systemic inflammation (LGSI) and androgens? SUMMARY ANSWER: miR-155 was associated with male subfertility independent of LGSI or androgens while miR-146a was only weakly associated with subfertility and LGSI. WHAT IS KNOWN ALREADY: Male subfertility has been associated with LGSI as well as with androgen deficiency. miR-155 and miR-146a are central regulators of inflammation and their level in cells and in the serum has been associated with several inflammatory conditions. STUDY DESIGN, SIZE, DURATION: In this case-control study, two independent groups of 60 subjects each (exploratory and confirmatory cohort) were randomly selected from an ongoing study on subfertile men (in total: hypogonadal; n = 40, eugonadal; n = 40 and control group n = 39) at a University Hospital Reproductive Medicine Centre. Individuals were matched for age. PARTICIPANTS/MATERIALS, SETTING, METHODS: Total RNA was isolated from cell-free serum. As internal control a synthetic miRNA, UniSp6, was added to each sample prior to extraction. miRNA expression levels were measured by real-time RT-PCR and presented as fold difference (arbitrary units, U) from control. Sera from these individuals had been previously analyzed for hormone and cytokine levels. MAIN RESULTS AND THE ROLE OF CHANCE: Serum levels of miR-155 were associated with levels of miR-146a (P < 0.0001), but only miR-146a was associated with inflammatory markers. miR-155 was strongly associated with subfertility (for subfertile group 1.88 U, 95% confidence interval (CI) 1.6-2.1 U versus 1.15, 95% CI 1.0-1.2 U in controls; P = 0.001). Receiver operating characteristic curve analysis indicated that miR-155 but not miR-146a can be used as a marker of subfertility. MiR-155 with a cutoff value of 1.77 had 47% sensitivity and 95% specificity for identifying subfertility and a positive predictive value (PPV) and negative predictive value (NPV) of 95 and 47%, respectively. When used in combination with FSH, sensitivity and specificity were 80 and 100%, respectively, while PPV and NPV were 100 and 71%, respectively, those values being higher than for the FSH alone. Repeating the results obtained in the exploratory cohort in an independent confirmatory cohort reduced the risk of a chance finding. LIMITATIONS, REASONS FOR CAUTION: Although the results from the exploratory cohort were confirmed in the confirmatory cohort, studies from other centers are needed to establish the role of miR-155 as a new biomarker of male fertility. Furthermore, the role of this marker in distinguishing between different groups of male subfertility is to be elucidated. WIDER IMPLICATIONS OF THE FINDINGS: Association of the inflammatory miRNA miR-155 with male fertility contributes to our understanding of the pathophysiology of subfertility and suggests a novel biomarker. Serum miR-155 in combination with FSH has higher diagnostic specificity and sensitivity compared with FSH alone. STUDY FUNDING/COMPETING INTERESTS: This work was supported by grants from Swedish Governmental Grant (ALF), Skane county council research and development foundation, Skane University Hospital Fonds and by the EU and Greek funds under the action 'Education and lifelong learning' program THALIS-FAT-VESSEL (No 379527). The authors have no competing interests to disclose.

Estrogen receptor alpha single nucleotide polymorphism as predictor of diabetes type 2 risk in hypogonadal men.

Estradiol (E2) is, apart from its role as a reproductive hormone, also important for cardiac function and bone maturation in both genders. It has also been shown to play a role in insulin production, energy expenditure and in inducing lipolysis. The aim of the study was to investigate if low circulating testosterone or E2 levels in combination with variants in the estrogen receptor alpha (ESR1) and estrogen receptor beta (ESR2) genes were of importance for the risk of type-2 diabetes. The single nucleotide polymorphisms rs2207396 and rs1256049, in ESR1 and ESR2, respectively, were analysed by allele specific PCR in 172 elderly men from the population-based Tromsø study. The results were adjusted for age. In individuals with low total (≤11 nmol/L) or free testosterone (≤0.18 nmol/L) being carriers of the variant A-allele in ESR1 was associated with 7.3 and 15.9 times, respectively, increased odds ratio of being diagnosed with diabetes mellitus type 2 (p = 0.025 and p = 0.018, respectively). Lower concentrations of E2 did not seem to increase the risk of being diagnosed with diabetes. In conclusion, in hypogonadal men, the rs2207396 variant in ESR1 predicts the risk of type 2 diabetes.

Non-reproductive effects of follicle-stimulating hormone in young men.

OBJECTIVE: Follicle-stimulating hormone (FSH) receptor expression has been reported in many extra-gonadal tissues, raising the question of non-reproductive effects of FSH. Because of increasing usage of FSH in treatment of male infertility, deeper knowledge of possible harmful off-target effects of FSH is warranted. METHODS: In total, 33 healthy young men (mean age 30 years) were included in the study. All received an s.c. injection of gonadotropin-releasing hormone (GnRH) antagonist and n = 16 were randomized to 300 IU recombinant FSH (300 IE 3 times/week) for 5 weeks at first visit (V1) whereas n = 17 served as controls. Blood samples were taken at (V1), after 3 weeks (V2), and after 5 weeks (V3), when the study ended. At V2, all subjects received 1000 mg testosterone undecanoate i.m. A standard set of bio- and inflammatory markers were compared between the groups using the Mann-Whitney test adjusted for multiple testing. RESULTS: As compared to controls, the FSH treated men had higher SHBG and albumin concentrations at V2 (p = 0.024 and 0.027, respectively), and lower levels of alanine aminotransferase (p = 0.026) and magnesium (p = 0.028) at V3. However, none of the results remained statistically significant after Bonferroni correction (p > 0.0011). CONCLUSIONS: FSH had no significant effects on non-reproductive organs when given in standard therapeutic doses to young men for 5 weeks. Therefore, the FSH treatment can be considered safe in otherwise healthy young men, constituting candidates for the infertility treatment with FSH.

Impact of add-back FSH on human and mouse prostate following gonadotropin ablation by GnRH antagonist treatment.

Objective: During androgen ablation in prostate cancer by the standard gonadotropin-releasing hormone (GnRH) agonist treatment, only luteinizing hormone (LH) is permanently suppressed while circulating follicle-stimulating hormone (FSH) rebounds. We explored direct prostatic effects of add-back FSH, after androgen ablation with GnRH antagonist, permanently suppressing both gonadotropins. Methods: The effects of recombinant human (rFSH) were examined in mice treated with vehicle (controls), GnRH antagonist degarelix (dgx), dgx + rFSH, dgx + flutamide, or dgx + rFSH + flutamide for 4 weeks. Prostates and testes size and expression of prostate-specific and/or androgen-responsive genes were measured. Additionally, 33 young men underwent dgx-treatment. Seventeen were supplemented with rFSH (weeks 1-5), and all with testosterone (weeks 4-5). Testosterone, gondotropins, prostate-specific antigen (PSA), and inhibin B were measured. Results: In dgx and dgx + flutamide treated mice, prostate weight/body weight was 91% lower than in controls, but 41 and 11%, respectively, was regained by rFSH treatment (P = 0.02). The levels of seminal vesicle secretion 6, Pbsn, Nkx3.1, beta-microseminoprotein, and inhibin b were elevated in dgx + rFSH-treated animals compared with only dgx treated (all P < 0.05). In men, serum inhibin B rose after dgx treatment but was subsequently suppressed by testosterone. rFSH add-back had no effect on PSA levels. Conclusions: These data provide novel evidence for the direct effects of FSH on prostate size and gene expression in chemically castrated mice. However, in chemically castrated men, FSH had no effect on PSA production. Whether FSH effects on the prostate in humans also require suppression of the residual adrenal-derived androgens and/or a longer period of rFSH stimulation, remains to be explored.

Estrogen receptor α single nucleotide polymorphism modifies the risk of azoospermia in childhood cancer survivors.

OBJECTIVE: Cancer treatment in childhood leads to permanent azoospermia in a significant number of boys and those who are diagnosed with cancer before puberty do not have the option of pretreatment cryopreservation of spermatozoa. However, there is an interindividual variation in the sensitivity to gonadotoxic effects of cancer therapy, which probably is due to genetic factors. Identification of genetic markers for the risk of azoospermia in childhood cancer survivors may help in identifying boys to whom testicular cryopreservation should be offered. METHODS: Fifty-one single nucleotide polymorphisms (SNPs) being markers of 12 different haplotype blocks in the androgen receptor, estrogen receptor (ER) α and ER ß genes were examined in 127 adult childhood cancer survivors. RESULTS: In ERα, markers of one specific haplotype block (rs2207396, rs9340958, rs9340978) were associated with an increased risk of azoospermia. Compared with those with the GG genotype, patients being heterozygous for the A allele in rs2207396 had a significantly increased risk of azoospermia [odds ratio (OR): 3.8; 95% confidence interval: 1.5-9.5; P=0.008], this OR being even higher in the subgroup treated with alkylating drugs (OR: 8.8; 95% confidence interval: 2.1-36; P=0.004). In this subgroup, 48% of the patients carried the A allele of rs2207396, this proportion being 70% among the azoospermic patients. CONCLUSION: Use of genetic markers of high risk of posttreatment azoospermia may, in the future, prove an important clinical tool in selection of boys to whom preservation of testicular tissue before cancer therapy should be offered.

RUBIC (ReproUnion Biobank and Infertility Cohort): A binational clinical foundation to study risk factors, life course, and treatment of infertility and infertility-related morbidity.

BACKGROUND: Infertility affects 15%-25% of all couples during their reproductive life span. It is a significant societal and public health problem with potential psychological, social, and economic consequences. Furthermore, infertility has been linked to adverse long-term health outcomes. Despite the advanced diagnostic and therapeutic techniques available, approximately 30% of infertile couples do not obtain a live birth after fertility treatment. For these couples, there are no further options to increase their chances of a successful pregnancy and live birth. OBJECTIVES: Three overall questions will be studied: (1) What are the risk factors and natural life courses of infertility, early embryonic loss, and adverse pregnancy outcomes? (2) Can we develop new diagnostic and prognostic biomarkers for fecundity and treatment success? And (3) what are the health characteristics of women and men in infertile couples at the time of fertility treatment and during long-term follow-up? MATERIAL AND METHODS: ReproUnion Biobank and Infertility Cohort (RUBIC) is established as an add-on to the routine fertility management at Copenhagen University Hospital Departments in the Capital Region of Denmark and Reproductive Medicine Centre at Skåne University Hospital in Sweden. The aim is to include a total of 5000 couples equally distributed between Denmark and Sweden. The first patients were enrolled in June 2020. All eligible infertile couples are prospectively asked to participate in the project. Participants complete an extensive questionnaire and undergo a physical examination and collection of biospecimens (blood, urine, hair, saliva, rectal swabs, feces, semen, endometrial biopsies, and vaginal swabs). After the cohort is established, the couples will be linked to the Danish and Swedish national registers to obtain information on parental, perinatal, childhood, and adult life histories, including disease and medication history. This will enable us to understand the causes of infertility and identify novel therapeutic options for this important societal problem.

Testosterone replacement therapy in men who conceived with intracytoplasmic sperm injection: nationwide register study.

OBJECTIVES: Male hypogonadism is associated with higher risk of co-morbidity and premature mortality. It is, therefore, of utmost importance to identify young men who are at the highest risk of testosterone deficiency and who may benefit from preventive measures. In this context, infertile men constitute a high-risk group. The extent of testosterone replacement therapy (TRT) among infertile men, defined as men who have to undergo assisted reproduction for fatherhood, is currently unknown. Therefore, we evaluated the pattern of prescription of TRT in the years following child conception among men who have fathered children with the help of intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF). DESIGN: By sourcing data from national population registries, hazard ratio (HR) for subsequent TRT was assessed for IVF and ICSI-treated men and compared to those who conceived spontaneously with age Cox regression analysis adjusted for age, educational level and previous intake of medicines for metabolic diseases. RESULTS: ICSI and IVF fathers had increased incidence of newly prescribed TRT compared to fathers conceiving spontaneously (ICSI: HR = 3.81, 95% CI = 3.09-4.69, P < 0.001; IVF: HR = 1.54, 95% CI = 1.15-2.05, P = 0.003). After adjustment for prescription of medication for one or more components of the MetS prior to TRT, the risk estimates attenuated but remained robust both for ICSI-treated (HR = 3.17 (95% CI: 2.56-3.9) and IVF-treated men (HR = 1.06 (95% CI: 1.05-1.07). CONCLUSION: Men who have to utilise powerful techniques, such as ICSI for fathering children, may be at risk for testosterone deficiency. Routine endocrine evaluation of men seeking fertility treatment is hence warranted.

[Androgen insensitivity syndrome]. / Androgeninsensitivitetssyndrom.

BACKGROUND: Androgen insensitivity is caused by mutations in the androgen receptor gene, and is a common etiological factor to ambiguous genitalia in the newborn. This article discusses the role of androgens in sex differentiation, the structure and function of the androgen receptor, the genetic background to androgen insensitivity as well as clinical aspects. MATERIAL AND METHODS: The article is based on literature retrieved from PubMed, the androgen receptor mutation database and the authors' own research and clinical experience. RESULTS AND DISCUSSION: Androgen insensitivity encompasses a wide spectrum of clinical manifestations. Besides exclusion of possible differential diagnosis, the diagnostic work-up includes a clinical assessment of the androgen receptor's susceptibility to androgen stimulation as well as molecular genetic analysis of the androgen receptor gene. The condition should be managed with a multidisciplinary approach by teams competent to treat children with disorders of sexual development.

Androgen receptor gene CAG and GGN repeat lengths as predictors of recovery of spermatogenesis following testicular germ cell cancer treatment.

Spermatogenesis is an androgen-regulated process that depends on the action of androgen receptor (AR). Sperm production may be affected in men treated for testicular cancer (TC), and it is important to identify the factors influencing the timing of spermatogenesis recovery following cancer treatment. It is known that the CAG and GGN repeat numbers affect the activity of the AR; therefore, the aim of this study is to investigate if the CAG and GGN polymorphisms in the AR gene predict recovery of sperm production after TC treatment. TC patients (n = 130) delivered ejaculates at the following time points: postorchiectomy and at 6, 12, 24, 36, and 60 months posttherapy (T0, T6, T12, T24, T36, and T60). The CAG lengths were categorized into three groups, <22 CAG, 22-23 CAG, and >23 CAG, and the GGN tracts were also categorized into three groups, <23 GGN, 23 GGN, and >23 GGN. At T12, men with 22-23 CAG presented with a statistically significantly (P = 0.045) lower sperm concentration than those with other CAG numbers (8.4 × 106 ml-1 vs 16 × 106 ml-1 ; 95% CI: 1.01-2.65). This association was robust to omitting adjustment for treatment type and sperm concentration at T0 (P = 0.021; 3.7 × 106 ml-1 vs 10 × 106 ml-1 ; 95% CI: 1.13-4.90). The same trends were observed for total sperm number. The least active AR variant seems to be associated with a more rapid recovery of spermatogenesis. This finding adds to our understanding of the biology of postcancer therapy recovery of fertility in males and has clinical implications.

Impact of PCB and p,p'-DDE contaminants on human sperm Y:X chromosome ratio: studies in three European populations and the Inuit population in Greenland.

OBJECTIVE: Recent studies indicate that persistent organohalogen pollutants (POPs) may contribute to sex ratio changes in offspring of exposed populations. Our aim in the present study was to investigate whether exposure to 2,2 ,4,4 ,5,5 -hexachlorobiphenyl (PCB-153) and dichlorodiphenyldichloroethene (p,p -DDE) affects sperm Y:X chromosome distribution. SUBJECTS AND METHODS: We obtained semen and blood for analysis of PCB-153 and p,p -DDE levels from 547 men from Sweden, Greenland, Poland (Warsaw), and Ukraine (Kharkiv), with regionally different levels of POP exposure. The proportion of Y- and X-chromosome-bearing sperm in the semen samples was determined by two-color fluorescence in situ hybridization analysis. RESULTS: Swedish and Greenlandic men had on average significantly higher proportions of Y sperm (in both cohorts, 51.2%) and correspondingly higher lipid-adjusted concentrations of PCB-153 (260 ng/g and 350 ng/g, respectively) compared with men from Warsaw (50.3% and 22 ng/g) and Kharkiv (50.7% and 54 ng/g). In the Swedish cohort, log-transformed PCB-153 and log-transformed p,p -DDE variables were significantly positively associated with Y-chromosome fractions (p-values 0.04 and <0.001, respectively). On the contrary, in the Polish cohort PCB-153 correlated negatively with the proportion of Y-bearing fraction of spermatozoa (p=0.008). CONCLUSIONS: The present study indicates that POP exposure might be involved in changing the proportion of ejaculated Y-bearing spermatozoa in human populations. Intercountry differences, with different exposure situations and doses, may contribute to varying Y:X chromosome ratios.

Cadmium may impair prostate function as measured by prostate specific antigen in semen: A cross-sectional study among European and Inuit men.

We investigated the association between cadmium in blood and the concentration of the prostate specific antigen (PSA) in semen, including the modifying effects of zinc or the CAG polymorphism in the androgen receptor (AR). Blood and semen samples were collected from 504 partners of pregnant women in Greenland, Poland and Ukraine. We found an inverse trend between cadmium and PSA (log(ß) = -0.121, 95% confidence interval (CI): -0.213; -0.029, P = 0.0103) in Greenlandic men. Similar results were observed in men with a high number of CAG repeats (CAG 24) (log(ß) = -0.231, 95% CI: -0.363; -0.098, P = 0.0009). Inverse trends between cadmium and PSA were found when semen zinc concentrations were below the median value for men from Ukraine and Greenland. These outcomes suggest that cadmium may impair prostate function, as measured by PSA in semen, while high zinc levels and a low number of CAG repeats protects against this action.

An androgen receptor gene mutation (E653K) in a family with congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency as well as in partial androgen insensitivity.

An androgen receptor (AR) variant (E653K) was found in two unrelated Swedish families. One family had two girls affected with congenital adrenal hyperplasia (CAH) due to steroid 21-hydroxylase deficiency. The girls, who showed mild virilization in relation to their CYP21 genotype, had inherited the AR gene mutation from their father, who showed no symptoms of androgen insensitivity. The other family had a boy with partial androgen insensitivity and ambiguous genitalia, and he had inherited the AR gene mutation from his mother. The mutant receptor showed a transactivating capacity in the same range as the normal receptor at high concentrations of ligand (1 and 10 nM dihydrotestosterone), but absent or reduced transactivation at low levels (0.01 and 0.1 nM). The receptor variant was not found among 250 additional unselected Swedish men. Sequencing of the AR gene in five unrelated CAH girls with the I172N mutation in CYP21 and minimal virilization did not reveal any additional deviations from the normal reference sequence. In addition, there was no difference in lengths of the polymorphic CAG repeat in the AR gene between CAH girls with the I172N mutation who showed minimal and severe virilization, and we found no evidence of skewed X-inactivation. We conclude that AR gene mutations or polymorphisms are not a common factor influencing the degree of hyperandrogenic symptoms displayed by CAH girls, and that the AR E653K mutation is compatible with normal genital development, although it can cause genital malformations in susceptible individuals.

Linkage between androgen receptor gene CAG trinucleotide repeat length and testicular germ cell cancer histological type and clinical stage.

Sex hormones and/or gonadotropins may play a crucial role in the development of testicular germ cell cancer (TGCC). A direct link between this malignancy and endocrine factors has not been confirmed. We tested whether CAG and GGN repeats of the androgen receptor gene (AR) play a role in the aetiology or pathogenesis of TGCC. Eighty-three TGCC patients and 220 controls were included. Mean CAG or GGN lengths did not differ between the TGCC cases and controls. The proportion of males with CAG lengths above 25, indicative of reduced androgen sensitivity, was significantly lower among patients with pure seminomas and in the combined group of seminomas and mixed tumours compared with non-seminomas and controls. The median CAG length was higher if the tumour was metastasing at diagnosis. This is the first study showing an association between the AR polymorphism and histological type as well as the progression rate of TGCC.

Gene-environment interactions in male reproductive health: special reference to the aryl hydrocarbon receptor signaling pathway.

Over the last few decades, there have been numerous reports of adverse effects on the reproductive health of wildlife and laboratory animals caused by exposure to endocrine disrupting chemicals (EDCs). The increasing trends in human male reproductive disorders and the mounting evidence for causative environmental factors have therefore sparked growing interest in the health threat posed to humans by EDCs, which are substances in our food, environment and consumer items that interfere with hormone action, biosynthesis or metabolism, resulting in disrupted tissue homeostasis or reproductive function. The mechanisms of EDCs involve a wide array of actions and pathways. Examples include the estrogenic, androgenic, thyroid and retinoid pathways, in which the EDCs may act directly as agonists or antagonists, or indirectly via other nuclear receptors. Dioxins and dioxin-like EDCs exert their biological and toxicological actions through activation of the aryl hydrocarbon-receptor, which besides inducing transcription of detoxifying enzymes also regulates transcriptional activity of other nuclear receptors. There is increasing evidence that genetic predispositions may modify the susceptibility to adverse effects of toxic chemicals. In this review, potential consequences of hereditary predisposition and EDCs are discussed, with a special focus on the currently available publications on interactions between dioxin and androgen signaling.

Androgen receptor CAG repeat length modifies the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on receptor activity in human prostate cells.

Increased incidence of prostate cancer has been reported in men exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD acts through the aryl hydrocarbon receptor (AhR), which interacts with the androgen receptor (AR). The AR gene contains a polymorphic CAG repeat that influences its transcriptional activity. We investigated the influence of TCDD on prostate cancer cells (PC-3) and non-tumor prostate cells (PNT1A) on 5α-dihydrotestosterone-activated ARs containing CAG repeats within normal length range (16, 22, and 28). The AhR target gene CYP1A1 mRNA expression was induced by TCDD, but was not affected by the AR CAG length. TCDD had no effect on AR activity in PC-3 cells, whereas the shortest AR variant was induced by TCDD in PNT1A cells. In conclusion, the CAG length dependent effect of TCDD on AR activity in PNT1A, but not in PC-3 cells, indicates as a cell-specific effect of TCDD on AR activity.

Serum levels of perfluorinated compounds and sperm Y:X chromosome ratio in two European populations and in Inuit from Greenland.

This study investigated whether perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), which exhibit reproductive toxicity in experimental animals, affect sperm sex chromosome ratio. The Y:X ratio was determined by fluorescence in situ hybridization. Serum concentrations of PFOA and PFOS were measured in 607 men from Greenland, Poland and Ukraine using liquid chromatography-tandem mass spectrometry. Data was analyzed by linear and nonlinear regression. We observed no associations between PFOA and Y:X ratio (p=0.845 in a linear model, p=0.296 in a nonlinear model). A positive nonlinear association between PFOS and Y:X ratio was observed (p=0.016), with no association in a linear model (p=0.118). Analyzing the populations separately, a negative trend between categorized PFOS exposure and Y:X ratio was observed for the Inuit (B=-0.002, p=0.044). In conclusion, there was a negative trend between Y:X ratio and PFOS in the Inuit, while there was no association between PFOA and the Y:X ratio in adult men.

Environmental factors and testicular function.

Over the last decades there has been a dramatic increase in the incidence of some diseases associated with the male reproductive system, including poor semen quality, testicular cancer and congenital developmental abnormalities such as cryptorchidism and hypospadias, malformations of the urethra and scrotum respectively. Based on these observations one recurring theme is the concern that certain environmental chemicals and lifestyle related factors may play a role. Early fetal life is a particularly critical time period, when the endocrine system is established and organs are developing. Although available data does not yet allow recommending, evidence based, prophylactic and/or therapeutic measures to eliminate or reduce the possible negative impact of environment/lifestyle on the male reproductive capacity, it is prudent to limit exposures of people to hormonally active chemicals.

Persistent organic pollutants have dose and CAG repeat length dependent effects on androgen receptor activity in vitro.

Recently, the effect of exposure to persistent organic pollutants (POPs) on sperm concentration was only seen in men with a short androgen receptor (AR) gene CAG repeat. In order to investigate whether these effects could be observed also in vitro, we tested the impact of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (4,4'-DDE) on 5α-dihydrotestosterone activated ARs containing 16, 22 and 28 CAG repeats, respectively. Single exposure to 4,4'-DDE had the most pronounced effect on the AR activity containing 16 CAG repeats, whereas 28 CAG was the most sensitive variant when a mixture of the two compounds was added. Thus, our in vitro results have confirmed the in vivo data indicating a CAG repeat length dependent effect of endocrine disrupters on the AR activity.