Testosterone, SHBG and differential white blood cell count in middle-aged and older men.

OBJECTIVE

Low-grade chronic inflammation is increasingly being implicated in cardiovascular disease (CVD) etiology and may represent an alternative pathway through which testosterone and sex hormone-binding globulin (SHBG) influence CVD risk. We examined the associations between endogenous testosterone, SHBG and total and differential white blood cell (WBC) counts in men.

METHODS

Cross-sectional study of 2418 men aged 40-78 years from the Norfolk population of European Prospective Investigation into Cancer (EPIC-Norfolk) who had no history of CVD or cancer and complete data on sex hormones (total testosterone (TT), SHBG and free testosterone (FT)) and WBC counts. Associations between sex hormones and WBC counts were assessed using linear regression models.

RESULTS

Higher SHBG and TT levels were associated with lower WBC counts. After adjustment for age, BMI, smoking, physical activity and diabetes status, total WBC count decreased by 0.163 (95% CI -0.236; -0.091) and 0.102 (-0.170; -0.034) per standard deviation (SD) increase in SHBG and TT respectively. Associations of SHBG and TT with total WBC count were mainly accounted for by a lower granulocyte count (β coefficient=-0.132 (-0.194; -0.070) per SD increase in SHBG and β coefficient=-0.104 (-0.161; -0.046) per SD increase in TT). No associations between FT and total and differential WBC counts were found.

CONCLUSIONS

Endogenous TT and SHBG levels are inversely associated with total WBC and granulocyte count in middle-aged and older men. Even though the underlying mechanism and causal directionality requires further exploration, these results support a link between hormonal status and low-grade inflammation.