How are FTO and fertility related?

The FTO gene (Fat Mass and Obesity Associated) is best known for its strong link to obesity. Obesity itself significantly impacts fertility: in women it can cause hormonal imbalances, ovulatory dysfunction, and PCOS-like conditions; in men it is associated with reduced sperm quality and lower testosterone. Some studies suggest FTO variants may directly affect reproductive hormones (e.g., SHBG, testosterone) independent of BMI, but the evidence is mixed and not robust. Consumer DNA tests like MyBody-X can report FTO SNPs (e.g., rs9939609), but the predictive value for fertility is low. Fertility is multifactorial – age, lifestyle, hormonal status, and underlying medical conditions play far larger roles. Under German law (GenDG), these tests are lifestyle products, not diagnostic tools, and cannot replace medical evaluation. Anyone experiencing infertility should consult a reproductive specialist rather than rely on genetic test results. Evidence grade: human-moderate (GWAS for obesity, limited fertility studies).