Testicular function in a birth cohort of young men

STUDY QUESTION By investigating a birth cohort with a high ongoing participation rate to derive an unbiased population, what are the parameters and influences upon testicular function for a population not selected with regard to fertility? SUMMARY ANSWER While varicocele, cryptorchidism and obesity may impact on human testicular function, most common drug exposures and the presence of epididymal cysts appear to have no or minimal adverse impact. WHAT IS KNOWN ALREADY The majority of previous attempts to develop valid reference populations for spermatogenesis have relied on potentially biased sources such as recruits from infertility clinics, self-selected volunteer sperm donors for research or artificial insemination or once-fertile men seeking vasectomy. It is well known that studies requiring semen analysis have low recruitment rates which consequently question their validity. However, there has been some concern that a surprisingly high proportion of young men may have semen variables that do not meet all the WHO reference range criteria for fertile men, with some studies reporting that up to one half of participants have not meet the reference range for fertile men. Reported median sperm concentrations have ranged from 40 to 60 million sperm/ml. STUDY DESIGN, SIZE AND DURATION The Western Australian Pregnancy Cohort (Raine) was established in 1989. At 20–22 years of age, members of the cohort were contacted to attend for a general follow-up, with 753 participating out of the 913 contactable men. Of these, 423 men (56% of participants in the 20–22 years cohort study, 46% of contactable men) participated in a testicular function study. Of the 423 men, 404 had a testicular ultrasound, 365 provided at least one semen sample, 287 provided a second semen sample and 384 provided a blood sample. PARTICIPANTS/MATERIALS, SETTING, METHODS Testicular ultrasound examinations were performed at King Edward Memorial Hospital, Subiaco, Perth, for testicular volume and presence of epididymal cysts and varicoceles. Semen samples were provided and analysed by standard semen assessment and a sperm chromatin structural assay (SCSA) at Fertility Specialists of Western Australia, Claremont, Perth. Serum blood samples were provided at the University of Western Australia, Crawley, Perth and were analysed for serum luteinizing hormone (LH), follicular stimulating hormone (FSH), inhibin B, testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), estradiol, estrone