Reproductive function during summer and winter in Norwegian men living north and south of the Arctic circle

Light pollution: time to consider testicular effects

Technological advances have led to a modern-day lighting and smartphone revolution, with artificial light exposure at night increasing to levels never before seen in the evolutionary history of living systems on Earth. Light as a pollutant, however, remains largely unrecognized, and the reproductive effects of light pollution are mostly if not entirely unconsidered. This is despite the reproductive system being intricately linked to metabolism and the circadian system, both of which can be disturbed even by low levels of light. Here, we aim to change this perspective by reviewing the physiological and pathophysiological mechanisms by which light exposure alters the intricate hormonal, metabolic and reproductive networks that are relevant to reproductive toxicology. Nascent human studies have recently identified the photoreceptors responsible for the light dose relationship with melatonin suppression and circadian re-entrainment, directly shown the association between the alignment of light-dark cycles with activity-rest cycles on metabolic health and provided proof-of-principle that properly timed blue light-enriched and blue light-depleted delivery can accelerate circadian re-entrainment. With these advances, there is now a need to consider testicular effects of light pollution.

Fluctuations in Seminal Quality throughout the Year: How do Temperature, Humidity and Atmospheric Pressure Impact on Human Sperm Quality?

Background

Most studies evaluating the possible seasonal variation of semen quality have considered temperature as the only causal factor.

Aims

To assess possible seasonality in sperm quality and associations between semen parameters and several meteorological variables (temperature, humidity, apparent temperature and atmospheric pressure) in a large cohort of andrological patients.

Settings and Design

This was a retrospective, cross-sectional and correlational/descriptive study.

Materials and Methods

Patients (n: 15665) were categorised into four groups (summer, winter, spring and autumn) according to the date of assistance at the fertility centre. Daily values of temperature, apparent temperature, humidity and atmospheric pressure were provided by the National Weather System and were calculated as the average of the 74 days previous to semen collection (spermatogenic cycle).

Statistical Analysis Used

As appropriate, the results were analysed by analysis of variance/Kruskal-Wallis, Chi-square test, t-test/Mann-Whitney, forward conditional regression model and Spearman/Pearson's correlations.

Results

We detected seasonality effects on sperm count, total sperm count and total motile sperm count, with the highest values in winter and the lowest in summer. Correlation analysis showed that temperature, apparent temperature and humidity negatively correlated with semen parameters, being humidity the most powerful predictive meteorological variable.

Conclusion

Sperm quality is influenced by seasons; increased environmental temperature and humidity negatively affect semen quality.

Study of Semen Quality, Reproductive Hormone Levels, and Lipid Levels in Men From Arkhangelsk, a City in North of European Russia

Male populations in the European North of Russia have not previously been investigated for semen quality. The aim of this study was to evaluate semen parameters, reproductive hormone levels, and lipid levels in volunteers from the general urban population of the European North of Russia, to compare the data published for men from the neighboring Northern or Eastern European countries, and to evaluate associations between sperm quality and serum hormonal and lipid levels. Ninety-nine volunteers aged 23-63 years residing in the city of Archangelsk were enrolled in the study. All men had blood samples drawn and completed a questionnaire concerning their health status and lifestyle; 90 men delivered semen samples. The medians for semen volume, sperm concentration, progressive motility, and normal morphology were 3.0 ml, 42.12 million/ml, 43.8%, and 6.5%, respectively. Sperm parameters below normal threshold values were found in 38.9% of participants. It seems that the sperm quality in our study group was slightly worse than in men from Finland, Norway, Sweden, or Estonia, but very similar to that in men from Denmark or Poland. The significant negative correlations of luteinizing hormone levels and positive correlations of inhibin B levels with sperm concentration and progressive motility were revealed. Higher levels of luteinizing hormone and lower levels of inhibin B were found in participants with impaired compared to normal sperm quality. No reliable links were found between serum total cholesterol, triglyceride, high and low-density lipoprotein cholesterol, and semen parameters.

Association between meteorological variables and semen quality: a retrospective study

Spermatogenesis is a temperature-dependent process, and high summer temperatures have been linked to lower sperm concentration and count. However, reports describing the association between other meteorological variables and semen quality are scarce. This study evaluated the association between semen quality and temperature, humidity, pressure, apparent temperature (AT), temperature-humidity index (THI), simplified wet-bulb global temperature (sWBGT), and sunshine duration. Semen samples were obtained at the Laboratorio de Andrología y Reproducción (LAR, Argentina), from men undergoing routine andrology examination (n=11657) and computer-assisted sperm analysis (n=4705) following WHO 2010 criteria. Meteorological variables readings were obtained from the Sistema Meteorológico Nacional. Sperm quality parameters were negatively affected in summer when compared to winter. Additionally, there was a significant decrease in sperm kinematics between winter and spring. Branch and bound variable selection followed by multiple regression analysis revealed a significant association between semen quality and meteorological variables. Specifically, changes in sunshine duration and humidity reinforced the prognosis of semen quality. Highest/lowest sunshine duration and humidity quantiles resulted in decreased sperm concentration, count, motility, vitality and membrane competence, nuclear maturity, and sperm kinematics associated to highest sunshine duration and lowest humidity. Findings from this report highlight the relevance of environmental studies for predicting alterations in male reproductive health associated to variations in meteorological variables, especially considering the current climate changes around the planet due to global warming and its consequences for human health.

Sperm physiology varies according to ultradian and infradian rhythms

The spermatozoon must be physiologically prepared to fertilize the egg, process called capacitation. Human sperm samples are heterogeneous in their ability to capacitate themselves, which leads to variability between samples from the same or different donors, and even along the seasons. Here we studied sperm variation in the capacitation state according to the ability of capacitated spermatozoa to acrosome react upon stimulation (% ARi) and to be recruited by chemotaxis (% Chex). Both indirect indicators of sperm capacitation increased along the incubation time with fluctuations. Those capacitated sperm recruited by chemotaxis showed an ultradian rhythm with a cycle every 2 h, which might be influenced by unknown intrinsic sperm factors. Two infradian rhythms of 12 months for the % ARi and of 6 months for % Chex were observed, which are associated with the joint action of temperature and photoperiod. Thus, to avoid false negative results, human sperm samples are recommended to be incubated for a long period (e.g. 18 h) preferably in spring time. This innovative point of view would lead to better comprehend human reproductive biology and to think experimental designs in the light of sperm cyclicity or to improve sperm aptitude for clinical purposes.

Association between semen parameters and chance of fatherhood - a long-term follow-up study

BACKGROUND

Evaluation of male fertility includes standard semen analysis; however, there is uncertainty about the value of sperm parameters in predicting fertility.

OBJECTIVE

To evaluate the association between semen parameters and fatherhood during a long-time period.

MATERIALS AND METHODS

Semen parameters (total sperm count, concentration, motility, and morphology) and sperm DNA fragmentation Index (DFI) assessed on samples collected from 195 Norwegian men from the general population in 2001/2002 were matched with information about fatherhood until 2015, obtained from the Medical Birth Register. The parameters were dichotomized as normal vs. abnormal according to the WHO reference values from 1999 and 2010. Cut-offs at 20% and 30% were used for DFI.

RESULTS

Among men who had no children before 2003, those with normal progressive sperm motility had more often become fathers (WHO 1999, cut-off ≥50%, adjusted OR 2.8, 95% CI 1.3-6.1 and WHO 2010, cut-off ≥32%; aOR 4.2, 95% CI 1.1-15). Based on the WHO 1999 reference value, men with normal sperm concentration (≥20 × 10⁶ /mL) had more often become fathers (aOR 3.1, 95% CI 1.1-8.6). Men with progressive sperm motility ≥50% and concentration ≥20 × 10⁶ /mL did more often achieve fatherhood (aOR 8.4, 95% CI 2.1-34). For DFI, there was a borderline significance at cut-off 20% in the group of men who had ever been fathers (OR 2.7, 95% CI 1.0-7.0 p < 0.05).

DISCUSSION

The results indicate that sperm progressive motility, sperm concentration, and DFI are associated with fatherhood during a longer time period, with sperm motility being most consistent. Although the sample size is relatively small and our results should be replicated in larger studies, they may be of clinical relevance.

CONCLUSION

Semen parameters may have a diagnostic value not only in a short time frame but also for predicting future fertility potential.

Vitamin D and male reproductive system

Vitamin D deficiency is a highly prevalent worldwide condition and affects people of all ages. The most important role of vitamin D is the regulation of intestinal calcium absorption and metabolism of calcium and phosphorus to maintain muscle and bone homeostasis. Furthermore, in recent years it has been discovered that the vitamin D receptor (VDR) is widely distributed in many organs and tissues where vitamin D can perform other actions that include the modulation of the immune response, insulin secretion, anti-proliferative effect on cells of vascular smooth muscle, modulation of the renin-angiotensin-aldosterone system and regulates cell growth in several organs. The VDR is widely distributed in the male reproductive system. Vitamin D induces changes in the spermatozoa's calcium and cholesterol content and in protein phosphorylation to tyrosine/threonine residues. These changes could be involved in sperm capacitation. Vitamin D seems to regulate aromatase expression in different tissues. Studies analyzing seasonal variations of sex steroids in male populations yield conflicting results. This is probably due to the wide heterogeneity of the populations included according to age, systemic diseases and obesity.

Seasonal fluctuation in the secretion of the antioxidant melatonin is not associated with alterations in sperm DNA damage

A high sperm DNA fragmentation index (DFI) is associated with reduced fertility. DFI is influenced by the balance between reactive oxygen species and antioxidants. A circannual variation in melatonin, an antioxidant and free radical scavenger, could thus impact semen quality and fertility. The association between the major melatonin metabolite, urine 6-sulfatoxymelatonin (aMT6s), and DFI was analyzed in 110 Oslo men (south of the Arctic Circle) and 86 Tromsoe men (north of the Arctic Circle). Two semen analyses, summer and winter, and four urine samples (early/late summer; early/late winter), were analyzed. The associations between aMT6s in urine and DFI were characterized in a cross-sectional and longitudinal manner using correlation analysis and linear regression. Regardless of season and location, no significant correlations between aMT6s and DFI were observed. The correlation coefficients for associations between changes over time (early winter–early summer) in aMT6s and DFI were for the total cohort: rho = −0.08 (P = 0.322), for the Oslo cohort: rho = −0.07 (P = 0.485), and for the Tromsoe cohort: rho = −0.14 (P = 0.273), respectively. Similar results were seen when comparing late winter and late summer. There was no any statistically significant correlation between changes over time in aMT6s and DFI for men with DFI below and above the median value (10%), respectively. The seasonal variation in melatonin excretion seems not to have any impact on DFI.

CYP1A1, CYP3A5 and CYP3A7 polymorphisms and testicular cancer susceptibility

Testicular cancer (TC) incidence is increasing worldwide, but the aetiology remains largely unknown. An unbalanced level of oestrogens and androgens in utero is hypothesized to influence TC risk. Polymorphisms in genes encoding cytochrome P450 (CYP) enzymes involved in metabolism of reproductive hormones, such as CYP1A1, CYP3A5 and CYP3A7, may contribute to variability of an individual's susceptibility to TC. The aim of this case-control study was to investigate possible associations between different CYP genotypes and TC, as well as histological type of TC. The study comprised 652 TC cases and 199 controls of Norwegian Caucasian origin. Genotyping of the CYP1A1*2A (MspI), CYP1A1*2C (I462V), CYP1A1*4 (T461N), CYP3A5*3C (A6986G) and CYP3A7*2 (T409R) polymorphisms was performed using TaqMan allelic discrimination or sequencing. The CYP1A1*2A allele was associated with 44% reduced risk of TC with each polymorphic allele [odds ratio (OR) = 0.56, 95% confidence interval (CI) = 0.40-0.78, p(trend) = 0.001], whereas the CYP1A1*2C allele was associated with 56% reduced risk of TC with each polymorphic allele (OR = 0.44, 95% CI = 0.25-0.75, p(trend) = 0.003). The decreased risk per allele was significant for seminomas (OR = 0.46, 95% CI, 0.31-0.70, p(trend) < 0.001 and OR = 0.31, 95% CI = 0.14-0.66, p(trend) = 0.002, respectively), but only borderline significant for non-seminomas (OR = 0.65, 95% CI = 0.45-0.95, p(trend) = 0.027 and OR = 0.55, 95% CI = 0.30-1.01, p(trend) = 0.052, respectively). There were no statistically significant differences in the distribution of the CYP3A5*3C and CYP3A7*2 polymorphic alleles between TC cases and controls. This study suggests that polymorphisms in the CYP1A1 gene may contribute to variability of individual susceptibility to TC.

High risk of azoospermia in men treated for childhood cancer

Childhood cancer survivors (CCS) have an increased risk of impaired spermatogenesis, but data regarding the disease- and treatment-related risk factors of azoospermia are scarce. Such information is crucial both for counselling CCS and for selecting patients for testicular tissue cryopreservation. The proportion of azoospermic men in CCS was 18% [95% confidence interval (CI): 12-26], specifically for leukaemias (19%; 95% CI: 5.5-42), Hodgkin's disease (53%; 95% CI: 29-76), non-Hodgkin's lymphoma (11%; 95% CI: 0.28-48) and testicular cancer (11%; 95% CI: 0.28-48). In CCS treated with high doses of alkylating agents, the proportion of azoospermic men was 80% (95% CI: 28-99) and if radiotherapy was used additionally, the proportion was 64% (95% CI: 35-87). In CCS with subnormal Inhibin B levels, the proportion of azoospermic men was 66% (95% CI: 47-81) and for those with elevated follicle-stimulating hormone (FSH) levels, the proportion was 50% (95% CI: 35-67). Among CCS with subnormal testicular volume (≤ 24 mL), azoospermia was found in 61% (95% CI: 39-80) of the cases. Most childhood cancer diagnoses are associated with an increased risk of azoospermia, especially in CCS receiving testicular irradiation, high doses of alkylating drugs and other types of cytotoxic treatment, if combined with irradiation. Inhibin B, FSH and testicular volume can be used as predictors for the risk of azoospermia.

Are serum levels of vitamin D associated with semen quality? Results from a cross-sectional study in young healthy men

OBJECTIVE

To examine the association between low serum vitamin D concentration and estimates of male reproductive function.

DESIGN

Cross-sectional study.

SETTING

University hospital.

PATIENT(S)

From a Danish pregnancy cohort established in 1984-1987, 347 sons were selected for a study conducted in 2005-2006.

INTERVENTION(S)

Semen parameters and reproductive hormones were related to vitamin D concentrations in 307 men.

MAIN OUTCOME MEASURE(S)

Semen characteristics and reproductive hormones.

RESULT(S)

A high vitamin D level was unexpectedly associated with lower crude median total sperm count and percentage of normal morphology sperm and a high level of crude median sex hormone-binding globulin and FSH. After adjustment, the associations attenuated to nonsignificant associations, except for sex hormone-binding globulin. Additionally, adjusted free androgen index was lower at higher vitamin D levels, and men with high vitamin D had 11% (95% confidence interval, 1%-20%) lower free androgen index compared with men with low vitamin D.

CONCLUSION(S)

These results do not indicate that low vitamin D is a risk factor for poor semen quality in a population of young healthy men, but we may not have enough men with low vitamin D levels to detect an effect. New studies should include a larger proportion of vitamin D-deficient men.

Sperm DNA integrity in men treated for childhood cancer

PURPOSE

It is not known whether childhood cancer and its treatment are associated with sperm DNA damage, which subsequently affects fertility and might be transmitted to the offspring. The aim of this study is to assess DNA fragmentation index (DFI) as an indicator of sperm DNA integrity in childhood cancer survivors (CCS), with treatment regimen taken into account.

EXPERIMENTAL DESIGN

In 99 CCS and 193 age-matched healthy controls, DFI was assessed by using sperm chromatin structure assay.

RESULTS

In the whole group of CCS, DFI was increased compared with the controls, with borderline statistical significance [mean difference, 1.8%; 95% confidence interval (95% CI), -0.0088%-3.7%]. Those treated with radiotherapy only (mean difference, 6.0%; 95% CI, 1.6-10%) or surgery only (mean difference, 2.9%; 95% CI, 0.083-5.8%) had statistically significantly higher DFI than the controls. The odds ratio (OR) for having DFI >20%, which is associated with reduced fertility, was significantly increased in CCS compared with the control group (OR, 2.2; 95% CI, 1.1-4.4). For the radiotherapy-only group, the OR was even higher (OR, 4.9; 95% CI, 1.3-18). DFI was not associated with dose of scattered testicular irradiation or type of chemotherapy given.

CONCLUSIONS

DFI was increased in CCS, with those treated with chemotherapy being the only exception. This sperm DNA impairment may be associated with the disease per se rather than due to the treatment, and may have negative consequences in terms of fertility and risk of transmission to the offspring.

Single semen analysis as a predictor of semen quality: clinical and epidemiological implications

It is generally thought that a single ejaculate is a bad predictor of semen quality of a subject, because of significant intra-individual variation. Therefore, we investigated the degree to which the results of a first semen analysis differ from that of a second analysis among men from a general population in Norway. In addition, we analysed how the two different semen results mirrored the overall semen quality assessment. A total of 199 volunteers participated in the study and delivered two semen samples with an interval of 6 months. The semen parameters were determined according to the World Health Organization (WHO) 1999 guidelines, which were also used to determine whether semen quality was normal or abnormal. In addition, the DNA fragmentation index (DFI) was determined using the Sperm Chromatin Structure Assay. The two samples from each individual were very similar with regard to standard semen parameters and DFI (r(s:) 0.67-0.72), and there were no significant systematic differences between the two samples. The result of the first sample (normal/abnormal) was highly predictive of the overall conclusion based on the two samples (sperm concentration: in 93% of the cases (95% confidence interval [CI]: 89%-96%); sperm motility: in 85% of the cases (95% CI: 79%-89%); overall semen quality: in 85% of the cases (95% CI: 80%-90%). In epidemiological studies, one ejaculate is a sufficient indicator of semen quality in a group of subjects. In a clinical situation, when the question is whether the semen quality is normal or not, the first ejaculate will, in at least 85% of cases, give a correct overall conclusion.

Association between tobacco exposure and reproductive parameters in adolescent males

Cigarette smoking is quite prevalent in the general population but our knowledge of its effect on male reproductive function is still very limited. Therefore, we investigated the impact of tobacco exposure on reproductive characteristics in young males. Military conscripts, 217 non-smokers and 85 smokers, with a median age of 18 years were enrolled. Physical examination and semen analysis, including measurement of accessory sex gland markers and reproductive hormone levels, were performed. Lifestyle-associated factors, including maternal smoking during pregnancy and snuffing, were recorded. Non-smokers had 49% higher total sperm number than smokers (95% CI 4.5-112%, p = 0.01). In addition, sperm concentration was 37% higher among non-smokers (95% CI -4% to 95%, p = 0.08). Serum levels of follicle-stimulating hormone (FSH) were 17% higher among non-smokers (95% CI 3-33%, p = 0.02), whereas no significant differences between smokers and non-smokers were found for inhibin B, testosterone, sex hormone binding globulin, luteinizing hormone and oestradiol. Those who smoked >10 cigarettes per day exhibited 37% lower (95% CI 10-69%, p = 0.005) FSH levels than those who smoked less. Maternal smoking during pregnancy had a negative impact on epididymal and seminal vesicle marker secretion. Smoking seems to impair sperm production and epididymal as well as accessory sex gland function and could be one of the factors contributing to regional differences in sperm parameters.

Seasonal variation in serum concentrations of reproductive hormones and urinary excretion of 6-sulfatoxymelatonin in men living north and south of the Arctic Circle: a longitudinal study

OBJECTIVE

Seasonal variation in photoperiod or temperature may influence human reproductive biology. The present study evaluated whether seasonal changes occurred in the levels of reproductive hormones and the major melatonin metabolite, 6-sulfatoxymelatonin (aMT6s), in populations exposed to extreme variation in photoperiod and temperature.

DESIGN

Two separate cohorts of Norwegian men were recruited from the general population in either of two locations: Tromsø (69.5 degrees N, n = 92) or Oslo (60 degrees N, n = 112), located north and south of the Arctic Circle (66.5 degrees N), respectively.

MEASUREMENTS

Four blood and 12-h overnight urine samples were obtained on separate occasions over a 12-month period, including during the photoperiod maximum and minimum. Serum concentrations of FSH, LH, testosterone (T), oestradiol (E(2)), SHBG and the urinary excretion of aMT6s were assessed.

RESULTS

Statistical analysis using generalized estimating equations indicated that LH levels were lowest during early winter in both locations (both P = 0.01). In Tromsø, free T and E(2) concentrations peaked during early winter (P = 0.02 and 0.003, respectively). In Oslo, free T levels were lowest during early winter (P = 0.06) whereas E(2) levels were lowest during late summer (P < 0.001). Urinary aMT6s concentrations were lowest during early summer in Tromsø and Oslo. Concentrations peaked during early winter in Tromsø (P < 0.001) and during late winter in Oslo (P < 0.001).

CONCLUSIONS

LH levels exhibited similar changes in both locations, whereas the patterns of changes of the sex steroid concentrations differed, possibly indicating different underlying mechanisms. Excretion of aMT6s was lowest during early summer in both locations, indicating that the long natural photoperiod was sufficient to cause suppression of melatonin secretion. Whether these changes have any biological significance remains uncertain.

Longitudinal study of sperm DNA fragmentation as measured by terminal uridine nick end-labelling assay

BACKGROUND

One major limitation in the use of sperm DNA fragmentation as measured by the TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL) assay is the paucity of solid data on the stability of this parameter.

METHODS

The objective of our study was to evaluate variations in the degree of sperm DNA fragmentation, as measured by the TUNEL assay, over a 6 month period. Five donors provided semen samples (total 107) on the average three times per month, and 10 infertility patients provided semen samples every 4 weeks (total 58).

RESULTS

The mean percentage of sperm DNA fragmentation for donors was 13.18%, the within-donor standard deviation (SD(W) = 3.79%) was small compared to between-donor (SD(B) = 17.56%). For the group of patients, the mean percentage of sperm DNA fragmentation was 22.44%, with SD(W) of 4.43% within patients and SD(B) of 29.48% between patients. No seasonal rhythm was observed during the study. The intra-class correlation coefficient for all subjects combined was 0.83. Compared to sperm concentration, individual coefficients of variation for sperm DNA fragmentation indicated less variability in four subjects, but were similar in the others.

CONCLUSION

This longitudinal study shows that sperm DNA fragmentation is a parameter with good stability (repeatability) over time; it can be taken as a baseline both in healthy fertile men and in patients from infertility couples.