In a recent study published in journal Andrology, researchers compared reproductive traits in father-son pairs from Denmark and Finland, investigating familial resemblance patterns. Total fertility rates substantially declined in several countries, while previous research documented deteriorating semen quality in some populations, longitudinal analyses indicate decline in Finland.
No persistent trends in Denmark in recent decades, lifestyle, genetic, and environmental factors among possible contributors to changes in semen quality observed globally.
Genetic contribution to reproductive health remains poorly understood, with some evidence suggesting reproductive hormone levels in males are heritable, prompting father-son comparison investigation.
Cross-Sectional Comparison Of Father-Son Pairs From 1997-2002 Cohort
Researchers conducted cross-sectional comparison of father-son pairs, young males from Finnish-Danish Boy birth cohort, born in Finland or Denmark during 1997-2002, attended follow-up visit. The visit occurred with fathers at age 18-23 years during 2017-21, researchers evaluated height, weight, spermatic cord palpation, testicular size and position, penile width and length.
Anopenile distance APD, and anoscrotal distance ASD also measured, testicular size measured using ultrasonography USG and orchidometer for accuracy and comparison. APD, ASD, penile width measured using caliper, penile length measured using ruler, questionnaires administered before visit collecting information on general health and habits. Information included three-month smoking habits, alcohol intake, fever, history of gonorrhea, chlamydia, cryptorchidism, and maternal smoking during pregnancy for confounding adjustment.
Hormones Measured In Fasting Serum Samples
Reproductive hormones measured in fasting serum samples, assessed hormones were testosterone, inhibin B, luteinizing hormone LH, follicle-stimulating hormone FSH, and sex hormone-binding globulin SHBG. Hormone concentrations determined using immunoassays, while free testosterone calculated using Vermeulen equation, inhibin B/FSH, testosterone/LH, free testosterone/LH ratios calculated for analysis.
Participants instructed to abstain from ejaculation for two to seven days before providing semen samples, but some reported shorter intervals affecting motility.
Researchers assessed semen volume, sperm motility, sperm count, and morphology, Wilcoxon signed-rank test used to examine paired differences between sons and fathers statistically. Spearman correlation performed to examine relationships among reproductive traits between sons and fathers, linear mixed models used to assess familial resemblance adjusting for explanatory factors.
Models adjusted for various factors including height, weight, body mass index BMI, nationality, history of cryptorchidism, age, varicocele, smoking, abstinence time, examiner depending on outcome. Time from ejaculation to semen analysis considered for sperm motility, in sensitivity analyses five pairs with history of surgically corrected cryptorchidism excluded for robustness.
Findings
117 Father-Son Pairs Included
Study included 117 father-son pairs: 79 from Denmark and 38 from Finland, median age of fathers and sons was 52.2 and 19.6 years respectively.
Fathers had higher BMI 26.1 kg/m2 vs 21.5 kg/m2 and reported median weekly alcohol consumption six units, compared with one among sons. In addition, fathers more often rated health as excellent or good than sons, daily smoking in past three months more prevalent among sons.
Sperm concentration below 1 million/mL for five participants and below 15 million/mL for 23 additional subjects, indicating low counts in subset.
Fathers had higher FSH and SHBG levels, lower free and total testosterone levels, larger testes, and lower inhibin B/FSH, testosterone/LH, free testosterone/LH ratios than sons.
There were no significant generational differences in inhibin B or LH levels, fathers had higher total sperm counts and sperm concentrations, whereas sons greater proportion progressively motile sperm.
Proportion of sperm with normal morphology and semen volume did not differ between sons and fathers, fathers had larger APD, while sons had larger ASD.
Sensitivity analyses yielded similar results, familial resemblance analysis revealed significant correlations between sons and fathers for ultrasound-measured testicular size, LH levels, SHBG levels, inhibin B levels.
Correlations included FSH levels, sperm concentration, penile width, inhibin B/FSH ratio, free testosterone/LH ratio, testosterone/LH ratio, and APD, associations weak with adjusted intraclass correlation coefficients ranging 0.17 to 0.30.
In adjusted analyses, researchers observed no significant familial resemblance for total or free testosterone, total sperm count, sperm motility, semen volume, normal morphology, penile length, or ASD.
In sensitivity analyses, correlations for penile width and free testosterone/LH ratio became borderline significant, while orchidometer-measured testicular size became statistically significant and noteworthy.
Limited Familial Resemblance Identified
Study identified limited familial resemblance in reproductive traits, such as testicular size, sperm concentration, penile width, select hormones, and APD, in father-son pairs.
Researchers could not distinguish genetic influences from shared environmental or other familial factors, limitations include small sample size particularly from Finland and low participation rates.
Substantial age differences between fathers and sons, reliance on single semen sample, and self-reported information on cryptorchidism among fathers limit interpretation and generalizability. Sample too small to establish generational trends in semen quality, and fathers had demonstrated fertility, potentially affecting comparisons with sons and introducing selection bias.
Q&A
Q: What did Andrology study of father-son pairs from Denmark and Finland find about familial resemblance in reproductive traits?
A: Study of 117 pairs found limited weak familial resemblance for ultrasound testicular size, LH, SHBG, inhibin B, FSH, sperm concentration, penile width, hormone ratios, APD, ICC 0.17-0.30.
Q: How were reproductive traits like testicular size, APD, ASD, penile measurements and hormones assessed in father-son study?
A: Height weight palpation testicular size position measured via USG orchidometer, APD ASD width caliper length ruler, fasting serum testosterone inhibin B LH FSH SHBG immunoassays, free testosterone Vermeulen equation.
Q: Did study find significant differences between fathers and sons in testosterone, sperm counts, motility, and health behaviors?
A: Fathers higher FSH SHBG BMI alcohol consumption larger testes total sperm counts concentration, lower free total testosterone ratios, sons greater progressive motility daily smoking, similar morphology volume inhibin B LH.
FAQ
Q: Why is genetic contribution to male reproductive health poorly understood despite evidence hormone levels heritable?
A: Total fertility rates declined, semen quality deteriorating some populations, lifestyle genetic environmental factors possible contributors, but genetic contribution remains poorly understood, some evidence hormone levels heritable prompting further research.
Q: What is Finnish-Danish Boy birth cohort and when did father-son follow-up visits occur?
A: Young males from cohort born Finland or Denmark 1997-2002 attended follow-up visit with fathers at age 18-23 years during 2017-21 for evaluation of reproductive traits and questionnaires.
Q: What limitations affect Andrology father-son study including sample size and reliance on single semen sample?
A: Limitations include small sample particularly Finland, low participation rates, substantial age differences 52.2 versus 19.6 years, single semen sample, self-reported cryptorchidism fathers, demonstrated fertility fathers affecting comparisons, too small for generational trends.
Q: Which reproductive traits showed no significant familial resemblance between fathers and sons in adjusted analyses?
A: No significant resemblance for total or free testosterone, total sperm count, sperm motility, semen volume, normal sperm morphology, penile length, ASD, indicating limited inheritance for those traits.
Q: Could researchers distinguish genetic influences from shared environmental or familial factors in father-son resemblance?
A: No, researchers could not distinguish genetic influences from shared environmental or other familial factors, associations weak, indicating need for larger studies controlling lifestyle and environmental exposures more comprehensively.
Disclaimer: This article provides educational information based on study published in journal Andrology examining father-son reproductive traits and does not constitute professional medical, urological, or fertility advice, diagnosis, or treatment recommendation.
