Sex-hormones and brain volumes in middle-age men

Authors

• M Elbejjani
• P Schreiner
• D Siscovick
• S Sidney
• CE Lewis
• N Bryan
• LJ Launer

Abstract

Experimental research suggests that sex-hormones influence brain processes and that testosterone has neuro-protective actions in the brain. In older men, declining testosterone levels have been linked to neurocognitive and brain pathology. However, little is known on the relationships between sex-hormones and brain measures in middle age. We examined the relationships of testosterone (T) and sex hormone-binding globulin (SHBG) levels with global and regional brain volumes in 267 middle-age men participating in the Coronary Artery Risk Development in Young Adults CARDIA-brain magnetic resonance imaging sub-study. Sex-hormone levels were measured at the ages of 24 and 41 and brain volumes were measured at the ages of 42 to 56. Adjusted for potential confounders, higher SHBG levels were associated with larger total WM volumes (+3.15 cm3 (95% CI=0.01, 6.28)) for each z-score increase in SHBG level). There was a pattern of marginally non-statistically significant associations between higher total T and SHBG levels and smaller total GM volume. Some associations were more pronounced in certain regions: higher SHBG levels were associated with smaller GM volume in the parietal lobe (-1 cm3 (95%CI=-1.75, -0.24) and showed associations with larger frontal and temporal WM volumes and with smaller occipital GM volume. There were no indications of non-linear relations between hormones levels and brain volumes. Results support the hypothesized links between sex-hormones and brain outcomes and suggest associations in middle-age men between SHBG levels -which might reflect differential regulation of sex-hormones- and brain WM and GM volumes in regions linked to behavioral and neurocognitive outcomes.

Scientific Focus Area: Epidemiology

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