Changes in sex hormone levels in men may adversely affect hematocrit and contribute to an increased prevalence of thromboembolic stroke and anemia, according to researchers.

In a cross-sectional study of 1,273 men in the Third National Health and Nutrition Examination Survey (1988-1991), Adrian S. Dobs, MD, of the Johns Hopkins University School of Medicine in Baltimore, and colleagues found that men with low free testosterone levels had a significantly lower hematocrit than those with normal free testosterone levels.

The study, which was published in the Journal of Andrology (2012;33:1332-1341), found no association between total testosterone and hematocrit. Among men aged 20 and older, both low and high levels of sex hormone-binding globulin (SHBG) were associated with lower hematocrit. Among men aged 50 and older, only high SHBG levels were associated with lower hematocrit. In addition, high total and free estradiol levels were associated with higher hematocrit.

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Dr. Dobs’ team pointed out that both low and high hematocrit levels are associated with increased mortality and mortality, mediated via anemia and thromboembolic effects, respectively. Consequently, it is important to identify factors that influence hematocrit.