What role does Homocystein play in fertility?

Homocysteine is a sulfur-containing amino acid produced during methionine metabolism. Elevated homocysteine levels (hyperhomocysteinemia) have been associated with fertility issues, including recurrent pregnancy loss, preeclampsia, and poorer outcomes in assisted reproduction. In men, high homocysteine may impair sperm quality (motility, DNA integrity). The mechanisms are not fully understood but likely involve oxidative stress, endothelial dysfunction, and altered DNA methylation. Importantly, homocysteine is a modifiable risk factor: supplementation with folic acid, vitamin B12, and B6 can lower levels. However, supplementation should be medically supervised, as excessive folic acid may carry its own risks. The evidence comes mainly from observational studies and small trials; large randomized controlled trials are lacking. Thus, homocysteine is a useful biomarker but not a proven direct cause of infertility. Testing may be considered in the context of a comprehensive fertility workup, but it should not replace standard diagnostic procedures.