Background: This is the first large-scale Russian study describing semen quality and reproductive hormone levels among young men. Objectives:The aim of the study was to compare semen quality and reproductive hormone levels in young men of four cities and three ethnic groups living in the Siberian region of Russia and to find out ethnic or environmental reasons for regional differences. Materials and methods:The study population consisted of 1291 young men from Novosibirsk, Kemerovo, Ulan-Ude, and Yakutsk, including 1013 men of three most numerous ethnic groups: Slavs, Buryats, and Yakuts. Each participant provided one sperm and blood sample, information about lifestyle and ethnicity. Anthropometric parameters, semen quality and reproductive hormone levels, were evaluated.Results: Significant regional and ethnic differences were detected for semen and reproductive hormone parameters. Median sperm concentrations in Novosibirsk,

Background.Sperm morphology defects are considered to indicate several spermiogenesis anomalies, resulting in decreased men fertility, causing not only poor sperm morphology but also increased DNA fragmentation, chromatin condensation defects, increased oxidative stress. Consequently, detailed assessment of sperm morphological abnormalities in additional to counting percentage of sperm with normal morphology may be useful for andrologists and reproductive biologists. However, a little attention is paid to studying a regional and especially ethnic variability in the incidence of the sperm morphology defects. The aim of this research was to estimate ethnic variability in percentages of the sperm morphology abnormalities in men from general population living in the Siberian region of the Russian Federation.Methods.Male volunteers of Buryat (n=195), Yakut (n=130), and Slavic (n=89) ethnicity from the general population from Ulan-Ude and Yakutsk at least 5 years were enrolled in the study. Percentages of sperm morphological defects (according to the classification provided by the WHO laboratory manual, 2010) are counted after staining native ejaculate smears by Diff-Quick kits. Results.Among sperm defect, amorphous (62.25±12.18%), elongated (10.61±8.62%), pyriform(8.61±9.17%), and vacuolated heads (10.31±6.77%), abnormal acrosome (20.43±12.67%), asymmetrical insertion neck (18.33±6,43%), thick midpiece (6.21±3,41%), bent head (5.94±4,02%) and coiled tail (10.8±6.79%) were most frequent. In comparison with Buryats, Slavs and Yakuts were characterized by the decreased proportion sperm with normal morphology, the increased proportion of pyriform, elongated heads, abnormal acrosome, asymmertical tail insertion, excessive residual cytoplasm and increased teratozoospermia index (TZI). It was shown that impared progressive sperm motility and concentration associated with decreased percentage of sperm with normal morphology and increased proportion most of sperm morphology defects and TZI. However, increasing TZI in men with oligoastenozoospermia compared to men with astenozoospermia was revealed for Buryats only, suggesting ethnic features in the relationships between sperm morphology and concentration.Conclusion.The present study showed significant coordinated ethnic variability in the percentages of several sperm morphological defects in men from the general population located in Eastern Siberia. Damaged spermiogenesis processes underlying sperm head elongation and tail formation is considered to be significant contributors to geographical and ethnic variability of sperm morphology in men from the studied populations.