Evidence check: SHBG in the context of fatigue

SHBG (sex hormone-binding globulin) is a carrier protein for sex hormones. Altered SHBG levels may indirectly relate to fatigue, e.g., by affecting free testosterone or estradiol availability. Low SHBG is often linked to insulin resistance, metabolic syndrome, and low free testosterone, which can contribute to fatigue. High SHBG may reduce free testosterone in men. However, evidence is mostly observational and not causal. SHBG alone is not a direct marker for fatigue; comprehensive hormone and metabolic workup is needed. Caution against overinterpreting single lab values.