Sex hormone-binding globulin (SHBG) in plasma has been found to be significantly elevated in subjects with AD. We aimed to investigate whether plasma SHBG was associated with AD biomarkers and could predict neurodegeneration and clinical progression in prodromal AD. Methods: The study tested the cross-sectional relationship between plasma SHBG and CSF AD biomarkers in 707 non-demented adults. Next, the longitudinal influences of plasma SHBG at baseline on dynamic changes of CSF Aβ42,

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... volume, brain metabolism, and cognition were explored in 448 nondemented adults from the Alzheimer's disease Neuroimaging Initiative (ADNI). Finally, the influence of plasma SHBG on the risk of incident AD was explored. Results : This study included 707 participants (mean [SD] age, 62.5 [10.5] years, 416 [58.8%] female) from CABLE and 448 from ADNI-1 (mean [SD] age, 74.8 [7.2] years, 166 [37.5%] female). A positive correlation was found for SHBG levels in plasma and CSF (p = 2.12 × 10 -10, r = 0.44). Cross-sectional analyses indicated that individuals with higher plasma SHBG had lower levels of CSF Aβ42 (p < 0.005), after adjusting for age, gender, education, APOE4 allele, and cognitive scores. The longitudinal data showed that higher levels of plasma SHBG contribute to accelerated CSF Aβ42 decrease (p < 0.0005), brain metabolism decline (p < 0.05), hippocampus atrophy (p < 0.01), cognitive decline (p < 0.01), and higher risk of AD dementia (p < 0.05). Conclusions: Plasma SHBG is associated with CSF Aβ42 levels and could predict neurodegeneration and clinical progression in prodromal AD. This finding indicates plasma SHBG is a potentially useful, early biomarker for AD.