How are Selen and fertility related?

Selenium is an essential trace element that, via selenoproteins (e.g., glutathione peroxidases), supports antioxidant defense and thyroid metabolism – both relevant to fertility. In men, selenium deficiency can impair sperm quality (motility, morphology); some RCTs show improvement with supplementation in subfertile men. In women, selenium is linked to follicle maturation, oocyte quality, and pregnancy maintenance, but effects are smaller and evidence more heterogeneous. Excess selenium is toxic and can also impair fertility. Evidence is mostly from observational studies and a few RCTs; effect sizes are moderate. Genetic variants in selenoprotein genes (e.g., GPX1) may modulate selenium status and individual response. A genetic test for such variants provides clues but does not replace blood selenium measurement. For the general population without proven deficiency, selenium supplementation to boost fertility is not recommended.