Evidence check: BDNF in the context of fertility

The provided context contains no direct evidence linking BDNF (Brain-Derived Neurotrophic Factor) to fertility. BDNF is a neurotrophin primarily known for neuronal plasticity, but it is also expressed in reproductive tissues. Some studies suggest potential roles in oocyte maturation, sperm quality, and embryo development; however, the evidence is largely mechanistic and insufficient for clinical recommendations. No validated biomarkers for BDNF in fertility exist in routine practice. The context snippets (e.g., stress SNP rs4680, longevity rs2764264, microbiome test) are not relevant to BDNF and fertility. Therefore, any claim about BDNF testing for fertility would be speculative. Evidence level: mechanistic/unclear. Consumers should be cautious: direct-to-consumer tests claiming BDNF links to fertility lack robust scientific backing.