Lærke Priskorn

Male Reproductive Disorders and Fertility Trends: Influences of Environment and Genetic Susceptibility.

It is predicted that Japan and European Union will soon experience appreciable decreases in their populations due to persistently low total fertility rates (TFR) below replacement level (2.1 child per woman). In the United States, where TFR has also declined, there are ethnic differences. Caucasians have rates below replacement, while TFRs among African-Americans and Hispanics are higher. We review possible links between TFR and trends in a range of male reproductive problems, including testicular cancer, disorders of sex development, cryptorchidism, hypospadias, low testosterone levels, poor semen quality, childlessness, changed sex ratio, and increasing demand for assisted reproductive techniques. We present evidence that several adult male reproductive problems arise in utero and are signs of testicular dysgenesis syndrome (TDS). Although TDS might result from genetic mutations, recent evidence suggests that it most often is related to environmental exposures of the fetal testis. However, environmental factors can also affect the adult endocrine system. Based on our review of genetic and environmental factors, we conclude that environmental exposures arising from modern lifestyle, rather than genetics, are the most important factors in the observed trends. These environmental factors might act either directly or via epigenetic mechanisms. In the latter case, the effects of exposures might have an impact for several generations post-exposure. In conclusion, there is an urgent need to prioritize research in reproductive physiology and pathophysiology, particularly in highly industrialized countries facing decreasing populations. We highlight a number of topics that need attention by researchers in human physiology, pathophysiology, environmental health sciences, and demography.

Habitual alcohol consumption associated with reduced semen quality and changes in reproductive hormones; a cross-sectional study among 1221 young Danish men.

Objective Study associations between three measures of alcohol consumption (recent, typical/habitual, binging), semen quality and serum reproductive hormones. Design Cross-sectional population based study. Setting and participants 1221 young Danish men, aged 18–28 years were recruited when they attended a compulsory medical examination to determine their fitness for military service from 2008 to 2012. Total alcohol consumption: (1) in the week preceding (habitual/typical) the visit (recent alcohol intake), (2) in a typical week and (3) frequency of ‘binge drinking’ (consuming more than 5 units/day)) in the past 30 days was estimated. Main outcome measures Semen quality (volume, sperm concentration, total sperm count, and percentages of motile and morphologically normal spermatozoa) and serum concentration of reproductive hormones (follicle-stimulating hormone, luteinising hormone, testosterone, sex hormone binding globulin, oestradiol, free testosterone and inhibin B). Results Sperm concentration, total sperm count and percentage of spermatozoa with normal morphology were negatively associated with increasing habitual alcohol intake. This association was observed in men reporting at least 5 units in a typical week but was most pronounced for men with a typical intake of more than 25 units/week. Men with a typical weekly intake above 40 units had a 33% (95% CI 11% to 59%) reduction in sperm concentration compared to men with an intake of 1–5 units/week. A significant increase in serum free testosterone with increasing alcohol consumption the week preceding the visit was found. Binging was not independently associated with semen quality. Conclusions Our study suggests that even modest habitual alcohol consumption of more than 5 units per week had adverse effects on semen quality although most pronounced associations were seen in men who consumed more than 25 units per week. Alcohol consumption was also linked to changes in testosterone and SHBG levels. Young men should be advised to avoid habitual alcohol intake.

Association Between Use of Marijuana and Male Reproductive Hormones and Semen Quality: A Study Among 1,215 Healthy Young Men

A total of 1,215 young Danish men aged 18-28 years were recruited between 2008 and 2012 when they attended a compulsory medical examination to determine their fitness for military service. The participants delivered a semen sample, had a blood sample drawn, and underwent a physical examination. They responded to questionnaires including information on marijuana and recreational drug use during the past 3 months (no use, use once per week or less, or use more than once per week). A total of 45% had smoked marijuana within the last 3 months. Regular marijuana smoking more than once per week was associated with a 28% (95% confidence interval (CI): -48, -1) lower sperm concentration and a 29% (95% CI: -46, -1) lower total sperm count after adjustment for confounders. The combined use of marijuana more than once per week and other recreational drugs reduced the sperm concentration by 52% (95% CI: -68, -27) and total sperm count by 55% (95% CI: -71, -31). Marijuana smokers had higher levels of testosterone within the same range as cigarette smokers. Our findings are of public interest as marijuana use is common and may be contributing to recent reports of poor semen quality.

Is Sedentary Lifestyle Associated With Testicular Function? A Cross-Sectional Study of 1,210 Men

Based on cross-sectional data on 1,210 healthy young Danish men, we investigated whether sedentary lifestyle was associated with testicular function (semen quality and reproductive hormones) independent of physical activity. The men were invited to participate in the study between 2008 and 2012, when they attended a compulsory medical examination to determine their fitness for military service. Information on sedentary behavior (television watching and computer time) and physical activity was obtained by questionnaire. The men had a physical examination, delivered a semen sample, and had a blood sample drawn. Time spent watching television, but not time sitting in front of a computer, was associated with lower sperm counts. Men who watched television more than 5 hours/day had an adjusted sperm concentration of 37 million/mL (95% confidence interval (CI): 30, 44) versus 52 million/mL (95% CI: 43, 62) among men who did not watch television; total sperm counts in those 2 groups were 104 million (95% CI: 84, 126) and 158 million (95% CI: 130, 189), respectively. Furthermore, an increase in follicle-stimulating hormone and decreases in testosterone and the testosterone/luteinizing hormone ratio were detected in men watching many hours of television. Self-rated physical fitness, but not time spent on physical activity, was positively associated with sperm counts.

Dynamic GnRH and hCG testing: establishment of new diagnostic reference levels

OBJECTIVE Gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) stimulation tests may be used to evaluate the pituitary and testicular capacity. Our aim was to evaluate changes in follicular-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone after GnRH and hCG stimulation in healthy men and assess the impact of six single nucleotide polymorphisms on the responses. DESIGN GnRH and hCG stimulation tests were performed on 77 healthy men, 18-40 years (reference group) at a specialized andrology referral center at a university hospital. The potential influence of the tests was illustrated by results from 45 patients suspected of disordered hypothalamic-pituitary-gonadal axis. METHODS Baseline, stimulated, relative and absolute changes in serum FSH and LH were determined by ultrasensitive TRIFMA, and testosterone was determined by LC-MS/MS. RESULTS For the reference group, LH and FSH increased almost 400% and 40% during GnRH testing, stimulated levels varied from 4.4 to 58.8 U/L and 0.2 to 11.8 U/L and FSH decreased in nine men. Testosterone increased approximately 110% (range: 18.7-67.6 nmol/L) during hCG testing. None of the polymorphisms had any major impact on the test results. Results from GnRH and hCG tests in patients compared with the reference group showed that the stimulated level and absolute increase in LH showed superior identification of patients compared with the relative increase, and the absolute change in testosterone was superior in identifying men with Leydig cell insufficiency, compared with the relative increase. CONCLUSIONS We provide novel reference ranges for GnRH and hCG test in healthy men, which allows future diagnostic evaluation of hypothalamic-pituitary-gonadal disorders in men.

Self-reported onset of puberty and subsequent semen quality and reproductive hormones in healthy young men

STUDY QUESTION Is there an association between pubertal onset and subsequent reproductive health in young men? SUMMARY ANSWER Self-reported later onset of puberty was associated with reduced semen quality and altered serum levels of reproductive hormones among 1068 healthy, young Danish men. WHAT IS KNOWN ALREADY The long-term effects of variations in the onset of male puberty on subsequent reproduction remain largely unstudied. STUDY DESIGN, SIZE, DURATION In a cross-sectional study, young healthy Danish men were approached when they attended a compulsory medical examination to determine their fitness for military service from 2008 to 2012. PARTICIPANTS/MATERIALS, SETTINGS, METHODS A total of 1068 healthy, young Danish men (mean age 19 years) participated. They were asked to assess whether onset of penile and testicular growth, development of pubic hair and voice break occurred earlier, at the same time as or later than their peers. Their semen quality (semen volume, sperm concentration, total sperm count and percentages of motile and morphologically normal spermatozoa) and serum concentrations of sex hormones (LH, FSH, total testosterone, SHBG, inhibin B) and testicular size were determined. MAIN RESULTS AND THE ROLE OF CHANCE The response rate was 29%. Of the 1068 men who then participated, 652 answered the questions about penile growth and pubic hair development and were therefore included in the analysis. Self-reported later onset of puberty was associated with a 25% reduction in sperm concentration (95% CI -41%; -4%), a 40% reduction in total sperm count (-55%; -21%), a 1.6% age point reduction in morphological normal spermatozoa (-2.9; -0.3) and a 1.6 ml reduction in testicular size (-2.4 and -0.8 ml), after adjustment for confounders. Self-reported later onset of puberty was also associated with a 9% (3%; 15%) reduction in free testosterone and a 16% (2%; 31%) increase in FSH, after adjustment for confounders. LIMITATIONS, REASON FOR CAUTION Our study was cross-sectional and reverse causality cannot be ruled out. In addition, we cannot rule out the possibility that the men with late puberty onset had not yet fully matured although most were in Tanner stage 5. WIDER IMPLICATIONS OF THE FINDINGS Approximately 15% of young Danish men have self-reported later onset of puberty than their peers. We found poorer testicular function in young men with a history of later pubertal development, suggesting that timing of pubertal onset may be a fundamental marker of male reproductive health. However, we cannot exclude the possibility that these men had not fully matured at the time of examination and therefore their semen quality may yet improve, which makes follow-up important. STUDY FUNDING/COMPETING INTERESTS This work was supported by the Danish Council for Strategic Research, Program Commission on Health, Food and Welfare (project number 2101-08-0058), Rigshospitalet (grants 961506336 and R42-A1326), European Union, DEER (grant agreement no 212844), the Danish Ministry of Health and the Danish Environmental Protection Agency and Kirsten and Freddy Johansens Foundation (grant 95-103-72087). There are no competing interests.

Temporal Trends in Fertility Rates: A Nationwide Registry Based Study from 1901 to 2014

Objective Increasing age at first childbirth has been suggested to increase the risk for infertility. Our objective is to determine whether women above thirty years of age historically have been able to sustain fertility rates above replacement level. Design A descriptive nationwide Danish study using birth registries from 1901–2014. Setting Information on women’s age at childbirth was obtained by using records from primary, secondary and tertiary institutions. Participants Mothers to 8,024,969 live births. Main outcome measures Mothers were stratified according to age at childbirth to determine total and age specific fertility rates. Results Total fertility rate (TFR) decreased from 4.1 to 1.8 children per woman and age specific fertility also decreased from 1901 to 2014. Women aged 30–34, 35–39 or 40–44 years in the first decade of the 20th century had higher fertility rates than the corresponding five year younger age groups (25–29, 30–34 and 35–39, respectively) have had for the last 65 years. On average, women gave birth to two children after the age of 30 and one or more child after 35 years of age in the beginning of the 1900s. Furthermore, women more than 40 years of age accounted for 10% of TFR in 1901 compared with 4% in 2014 despite usage of assisted reproduction. Conclusion This nationwide study shows that women above 30 years of age historically have been able to sustain fertility rates above replacement level. This implies that other factors besides age are strong determinants of fertility in women above 30 years of age.

Influence of marital status on testosterone levels–A ten year follow-up of 1113 men

Based on a large population of 1113 men aged 30-60 at baseline (mean: 44.1 years, standard deviation: 10.5), we investigated whether intra-individual changes in testosterone (T) and related reproductive hormones during a ten year period were dependent of marital status at baseline and follow-up. The studied men were part of a health survey in Denmark, conducted between 1982 and 1984 with a follow-up examination approximately ten years later. Data on reproductive hormones, measured in serum, and lifestyle and marital status were obtained at both time points. As expected, an age-related decline in testosterone was observed. However, independent of age and lifestyle, we observed that men who went from unmarried to married (n=81) during the study period experienced an accelerated age-related decline in testosterone (-6.6nmol/L) whereas men who went from married to unmarried (n=67) experienced an attenuated age-related decline (-2.3nmol/L). Men who were either married or unmarried at both time points (n=167, n=798, respectively) had a testosterone decline in between (-3.7nmol/L and -4.6nmol/L, respectively). Changes in T/LH ratio did not differ according to marital status indicating that the lowered T level is not compensated by increasing LH levels. This could suggest a modification of the gonadostat due to an adaptation to changing life circumstances.

Parental age at delivery and a man's semen quality

STUDY QUESTION Is parental age at delivery associated with a mans semen quality? SUMMARY ANSWER In this large register-based study both mothers and fathers age are found to have minimal effects on semen quality in men. WHAT IS KNOWN ALREADY Both maternal and paternal age have been associated with a range of adverse health effects in the offspring. Given the varied health effects of parental age upon offspring, and the sensitivity of genital development to external factors, it is plausible that the age of a mans mother and father at conception may impact his reproductive health. To our knowledge this is the first examination of the effects of parental age on semen quality. STUDY DESIGN, SIZE, DURATION A retrospective cohort study of 10 965 men with semen data and parental data. PARTICIPANTS/MATERIALS, SETTING, METHODS The study was based on Danish men referred to the Copenhagen Sperm Analysis Laboratory due to infertility in their partnership. Men born from 1960 and delivering a semen sample until year 2000 were included. The men were linked to the Danish Civil Registration System to obtain information on parents age at delivery. Logistic regression analyses were used to calculate odds ratios and 95% confidence intervals for impaired semen quality. Linear regression analyses were used to examine a relationship between semen parameters and paternal age. MAIN RESULTS AND THE ROLE OF CHANCE There were no convincing effect of either mothers or fathers age on a mans semen quality. As no trends were noted, the few statistically significant results are likely attributable to chance. LIMITATIONS, REASONS FOR CAUTION Information regarding individual subject characteristics which may impact sperm production (i.e. smoking, BMI) were not available. While our sample size was large, we cannot exclude the possibility that a trend may have been identified with a still larger sample. In addition, the Danish Civil Registration System is merely administrative and hence does not discriminate between biological and adopted children. However, the low rate of adoption (≈2%) suggests that misclassification would have a minimal impact. The men were all referred to the laboratory for infertility problems in their partnership and, therefore, do not represent the general population. We, however, compared semen quality among men within the cohort, and it is therefore less important whether they, in fact, represent the general population. WIDER IMPLICATIONS OF THE FINDINGS The current study found no link between parental age and a sons semen quality, suggesting other factors may explain recent impairments in mens reproductive health. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the Hans and Nora Buchards Fund and the Kirsten and Freddy Johansens Fund. No competing interests. TRIAL REGISTRATION NUMBER Not relevant.

Possible involvement of the glucocorticoid receptor (NR3C1) and selected NR3C1 gene variants in regulation of human testicular function

Perceived stress has been associated with decreased semen quality but the mechanisms have not been elucidated. It is not known whether cortisol, the major stress hormone in humans, can act directly via receptors in the testis, and whether variants in the gene encoding the glucocorticoid receptor (NR3C1) can possibly modulate the effect. To address these questions, we investigated the expression of the glucocorticoid receptor in human testicular tissue, including adult and fetal samples (n = 20) by immunohistochemical staining, and in silico analysis of publicly available datasets. In the adult testis NR3C1 protein was detected in peritubular cells, a subset of Leydig cells, Sertoli cells (weak), and spermatogonia, but not in spermatids. The NR3C1 expression pattern in fetal testis samples differed by a notably stronger reaction in Sertoli cells, lack of staining in gonocytes but the presence in a subset of pro‐spermatogonia, and the almost absent reaction in nascent peritubular cells. In parallel, we explored the association between adult testicular function and three single nucleotide NR3C1 polymorphisms (BcII [rs41423247], 9β [rs6198], and Tth111I [rs10052957]) affecting glucocorticoid sensitivity. Testicular function was determined by semen analysis and reproductive hormone profiling in 893 men from the general population. The NR3C1 SNP BclI was associated with semen quality in an over‐dominant manner with heterozygotes having better semen parameters compared to both homozygote constellations, and with sperm motility showing the strongest association. This association was supported by a higher inhibin B and inhibin B/FSH ratio, as well as a lower FSH in BclI heterozygotes. The SNPs 9β and Tth111I were not associated with semen parameters. Although the clinical impact of the findings is limited, the results substantiate a suggested link between stress and testicular function. Hence this investigation should be regarded as a discovery study generating hypotheses for future studies.