Father–Son Comparison of Reproductive Traits

ABSTRACT Background Little is known about the relative contribution of genetic and environmental factors on male reproductive function. Objectives We studied in a cross‐sectional setting, whether testicular function and genital size correlate in father–son pairs. The study included young men from a prospective Finnish–Danish Boy cohort study and their fathers. Materials and Methods We collected data on young men born between 1997 and 2002 at Turku University Hospital, Finland, and at the University Hospital of Copenhagen, Denmark. These young men were invited for an adult follow‐up visit at 18–23 years together with their fathers. Altogether 38 Finnish and 79 Danish father–son pairs participated in the study. The study visits included analysis of a semen sample, measurement of serum reproductive hormones and genital size (testes, penis, anogenital distance [AGD]). Intraclass correlation coefficients (ICCs) were used to evaluate familial resemblance between fathers and sons. Results In the adjusted analyses, weak significant positive correlations between fathers and sons were observed in testicular volume measured by ultrasonography (ICC 0.30), concentrations of inhibin B (ICC 0.25), FSH (ICC 0.24), LH (ICC 0.22), and SHBG (ICC 0.26), sperm concentration (ICC 0.21), and anopenile distance (ICC 0.19). Penile width (ICC 0.23) showed significant father–son correlation, but it was of borderline statistical significance when pairs with cryptorchidism that had required surgical correction ( n = 5) were excluded. Father–son correlation for testicular size based on orchidometer (ICC 0.16) was statistically significant only when excluding pairs with a history of cryptorchidism (ICC 0.18). Conclusion In conclusion, while genetics contributes to reproductive health, the studied reproductive variables showed rather weak correlations between fathers and sons.