The relationship between anogenital distance and the efficacy of varicocele repair

Anogenital distance is associated with semen quality but not reproductive hormones in 1106 young men from the general population

STUDY QUESTION

Is anogenital distance (AGD) associated with semen quality and reproductive hormones in men from the general population?

SUMMARY ANSWER

Short AGD measured from the anus to the base of scrotum (AGDAS) was associated with reduced sperm counts and morphology but not with sperm motility or reproductive hormones.

WHAT IS KNOWN ALREADY

AGD is longer in males than in females. In rodents, AGD is a well-established and sensitive marker of disruption during the masculinization programming window in utero and it has been suggested to be so in humans as well. Therefore, the average AGD would be expected to be shorter in men with poor semen quality, which some studies have confirmed while others have not.

STUDY DESIGN, SIZE, DURATION

This cross-sectional population-based study was of 1106 men included between 2012 and 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Men from the general Danish population (median age 19 years), unselected with regard to fertility status and semen quality, delivered a semen sample, had a blood sample drawn, which was analyzed for concentrations of reproductive hormones, and answered a comprehensive questionnaire. They also had a physical examination performed including determination of AGD measured as the distance between anus and scrotum (AGDAS) and penis (AGDAP). Odds ratios (OR) and 95% CI were estimated for a man having abnormal semen parameters according to the World Health Organization's reference values or a low/high concentration of reproductive hormones (defined as the lowest or highest 10%) depending on AGD. AGD was categorized in four strata: ≤10th percentile, 10th-30th percentile, 30th-50th percentile and >50th percentile.

MAIN RESULTS AND THE ROLE OF CHANCE

Men with the 10% shortest AGDAS had a more than doubled risk (OR: 2.19, 95% CI: 1.40-3.42) of being in the subfertile range for either sperm concentration (<15 million/mL) or sperm morphology (<4%) compared to men with AGDAS above the median (reference). Men in the 10th-30th percentile also had an increased OR of 1.48 (95% CI: 1.06-2.08) but not men in the 30th-50th percentile (OR: 1.14, 95% CI: 0.81-1.62). AGDAP was only weakly related to semen quality. AGD was not associated with testicular volume or any of the reproductive hormones.

LIMITATIONS, REASONS FOR CAUTION

Limitations include the potential non-differential misclassification of reproductive outcomes based on a single semen and blood sample and some between-examiner differences in AGD measurements which introduces noise and may result in an underestimation of observed associations.

WIDER IMPLICATIONS OF THE FINDINGS

Our study of men from the general population confirmed associations between AGD and semen quality, supporting the hypothesis that AGD in humans could be a marker of fetal testicular development. This suggests that the low semen quality in Danish men may partly be explained by prenatal factors.

STUDY FUNDING/COMPETING INTEREST(S)

The study has received financial support from the ReproUnion (L.P.); the Research fund of Rigshospitalet, Copenhagen University Hospital (N.J.); Grants R01ES016863-04 and R01ES016863-02S4; National Institute of Environmental Health Sciences (NIEHS) and National Institute of Environmental Health Sciences grant (P30ES023515) (S.S.); the European Union (Contract numbers BMH4-CT96-0314, QLK4-CT-1999-01422, QLK4-CT-2002-00603, FP7/2007-2013, DEER Grant agreement no. 212844); the Danish Ministry of Health; the Danish Environmental Protection Agency; A.P. Møller and wife Chastine McKinney Møllers foundation; and Svend Andersens Foundation. None of the funders had any role in the study design, collection, analysis or interpretation of data, writing of the paper or publication decisions. The authors have nothing to declare.

TRIAL REGISTRATION NUMBER

N/A.

Prevalence of varicocoele and its association with body mass index among 39,559 rural men in eastern China: a population-based cross-sectional study

Varicocoele is a common cause of male infertility. We undertook a population-based cross-sectional study to evaluate the prevalence of varicocoele among rural men in eastern China and its association with body mass index. A total of 39,559 rural men in six counties in Beijing, Guangdong and Shandong provinces were recruited from 2011 to 2012. The presence and severity of varicocoele were measured by physical examinations. Univariate and multivariate logistic regression models were constructed to assess the association between varicocoele and body mass index after adjusting for possible confounders. Varicocoele was diagnosed in 1911 of 39,559 participants with an overall prevalence of 4.83%. The prevalence of varicocoele was highest in underweight (6.29%) and lowest in obese patients (3.71%, p < 0.05). The prevalence also decreased as body mass index increased in all three varicocoele grades. In multivariate logistic regression analysis after adjusting for region, age, height, occupation, cigarette smoking and alcohol consumption, body mass index was still inversely and independently associated with varicocoele (p < 0.001). Compared with normal weight men, underweight men (OR = 1.34; 95% CI, 1.10-1.63) were more likely to have varicocoele, whereas overweight men (OR = 0.88; 95% CI, 0.79-0.99) and obese men (OR = 0.75; 95% CI, 0.58-0.97) were less likely to have varicocoele. This study revealed that the prevalence of varicocoele was 4.83% among rural men in eastern China; body mass index was inversely and independently associated with the presence of varicocoele. Future efforts should be made to validate the risk factors for varicocoele and strengthen the prevention and treatment of varicocoele, especially in underweight men.

Anogenital distance as a measure of human male fertility

PURPOSE

In humans, recent studies have correlated anogenital distance (AGD) in adult men to testicular function. While studies of a group of men suggest an association, the utility of AGD in an infertility evaluation remains uncertain. We sought to determine the utility of AGD to predict male fertility.

METHODS

Between 2010 and 2011, men were recruited at a urology clinic to participate. AGD was measured using digital calipers in men being evaluated at a urology clinic. ANOVA and ROC analyses were used to determine correlations between AGD, fatherhood status, and semen parameters.

RESULTS

In all, 473 men were included in the analysis with a mean age of 43 ± 13 years. Anogenital distance was significantly longer in men with higher sperm concentration, total sperm count, and total motile sperm count. In order to evaluate the discriminating ability of AGD, ROC curves were created comparing AGD and total testis volume. The area under the curve (AUC) was significantly larger for total testis volume compared to AGD when evaluating fertility (0.71 vs 0.63, p = 0.02). Similarly, there was a trend towards a higher AUC for testis volume compared to AGD for sperm concentration and total sperm count. Stratification of men with long/short AGD and large/small testes also did not improve the predictive value of AGD.

CONCLUSIONS

While AGD is associated with sperm production on a population level, at the individual level the distinction based AGD alone cannot accurately estimate the efficiency of spermatogenesis.

Evidence for sexually dimorphic associations between maternal characteristics and anogenital distance, a marker of reproductive development

Data from animal models, historical cohorts, and modern epidemiologic studies have suggested that maternal characteristics can affect reproductive health of offspring; however, distinguishing between prenatal and postnatal contributions is difficult. Anogenital distance (AGD), the distance from the anus to the genitals, is believed to be a biomarker of prenatal androgen exposure in many species, and in humans it has been associated with several adult reproductive health outcomes. We used data from a pregnancy cohort study conducted in 4 US cities from 1999-2005 to examine whether AGD measurements in infants were associated with maternal self-reported age at conception, age at menarche, age at first birth, parity, and gravidity. AGD was measured in 289 infants (140 male, 149 female) born to study participants. After adjustment for relevant covariates, in linear regression models stratified by infant sex, maternal age was positively associated with AGD in male infants (AGD, anus to penis: β = 0.50, P = 0.002; AGD, anus to scrotum: β = 0.29, P = 0.02) but not female infants. Parity was inversely associated with AGD (anus to scrotum; β = -1.68, P = 0.03) in male infants. No other maternal characteristic predicted AGD in either sex. The mechanism underlying the unexpected relationship between maternal characteristics and AGD is unknown; however, we suggest several possibilities for future study.

Maternal diet, prenatal exposure to dioxins and other persistent organic pollutants and anogenital distance in children

We investigated the potential endocrine disruptive effect of prenatal exposure to persistent organic pollutants (POPs) through maternal diet, by measuring anogenital distance in newborns and young children. We included 231 mothers and their newborns measured at birth from the Rhea study in Crete, Greece and the Hmar study in Barcelona, Spain and 476 mothers and their children measured between 1 and 2 years from the Rhea study. We used food frequency questionnaires to assess maternal diet and estimated plasma dioxin-like activity by the Dioxin-Responsive Chemically Activated LUciferase eXpression (DR-CALUX®) and other POPs in maternal samples. We defined a "high-fat diet" score, as a prenatal exposure estimate, that incorporated intakes of red meat, processed meat, fatty fish, seafood, eggs and high-fat dairy products during pregnancy. Increasing maternal "high-fat diet" score was related to increasing dioxin-like activity and serum concentrations of lipophilic persistent organic pollutants in maternal blood. An inverse dose-response association was found between "high-fat diet" score and anoscrotal distance in newborn males. The highest tertile of the maternal score was associated with -4.2 mm (95% CI -6.6 to -1.8) reduction in anoscrotal distance of newborn males, compared to the lowest tertile. A weak positive association was found between the "high-fat diet" score and anofourchetal distance in newborn females. In young children we found no association between maternal "high-fat diet" score and anogenital distances. In conclusion, maternal high-fat diet may be linked to high prenatal exposure to persistent organic pollutants and endocrine disruptive effects, resulting to phenotypic alterations of the reproductive system.

The relationship between anogenital distance and age

In humans, recent studies have correlated anogenital distance (AGD) in adult men to intrinsic testicular function. Although rodent studies suggest that AGD is determined in utero and remains constant in adult life, it is not certain if AGD remains constant across a man's adult life. We sought to determine if adult male AGD varies based on age. A cross-sectional study of men being evaluated at a men's health clinic. Anogenital distance (the distance from the posterior aspect of the scrotum to the anal verge) and penile length (PL) were measured using digital callipers. anova and linear regression were used to determine correlations between AGD, fatherhood status and age. In all, 473 men were included in the analysis with a mean age of 43 ± 13 years. The mean AGD for the group was 39 ± 13 mm. Anogenital distance did not vary between age categories for the entire group, for fathers, and for childless men. Moreover, penile length also remained constant across age categories. On adjusted analyses stratified by fatherhood status, there was no relationship between AGDp and age. The current cross-sectional study demonstrates that anogenital distance, defined as the distance from the posterior scrotum to the anal verge, is similar for men of different ages. As such, AGD may provide a measure for genital development and function throughout adult life. However, confirmation with longitudinal studies is needed.