Association between follicle-stimulating hormone receptor polymorphisms and reproductive parameters in young men from the general population. Running head: FSH receptor polymorphisms in men

Objective Follicle-stimulating hormone (FSH) regulates gametogenesis through binding to its receptor (FSHR). In women, the Thr307Ala and Asn680Ser polymorphisms in the FSHR gene affect reproductive function, but it is not clear whether they have any impact on spermatogenesis and have mainly been investigated in infertile men of varying ages. The aim of the present study was therefore to examine whether these genetic variants of the FSHR influence reproductive parameters in men from the general population. Methods Men aged 17-20 years (n=313) were genotyped. All men provided a semen sample and a blood sample for hormonal measurements and DNA extraction. They underwent a medical examination and analyses of possible associations between Thr307Ala and Asn680Ser polymorphisms and hormonal and sperm parameters were subsequently carried out. Results Men homozygous for Thr307/Asn680 had a lower mean serum FSH concentration (3.07 vs. 3.65 IU/l, P=0.009), and higher mean serum estradiol (94.0 vs. 86.1 pmol/l, P=0.001), sex hormone-binding globulin (33.6 vs. 31.3 nmol/l, P<0.0001), and total testosterone (19.1 vs.17.9 nmol/l, P<0.0001) concentrations compared with men with other genotypes. In addition, sperm concentrations (71.9×10 6 vs. 70.8×10 6 /ml, P=0.040) and the total sperm counts were higher (212×10 6 vs. 206×10 6 , P<0.0001) and their testes volumes were larger (left: 11.5 vs. 11.0 ml, P<0.0001; right: 12.4 vs. 11.6 ml, P=0.002). Conclusion As in women, the results from the present study indicate that variants of the FSHR influence reproductive parameters in men.