Association Between Sex Steroid Hormones and Hematocrit in a Nationally Representative Sample of Men
Low or high hematocrit levels are associated with increased morbidity and mortality, mediated via anemia or thromboembolic events, respectively. It is therefore important to identify factors that influence hematocrit. Although androgens are known to stimulate ...
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We did not have a hypothesis about the association between estradiol and hematocrit because to our knowledge, there is no direct mechanistic link between estradiol and erythropoiesis. Yet, we found that men with higher concentrations of total and free estradiol were less likely to have low hematocrits and more likely to have high hematocrits, even after adjustments for total testosterone level and percent body fat. We adjusted for testosterone, which is converted to estradiol via catalysis by aromatase in fat, to be able to determine the independent association for estradiol. Our results for estradiol are compatible with a clinical study of testosterone supplementation in hypogonadal men that found that 12 of 14 men with an elevated hematocrit also had elevated estradiol levels (Dobs et al, 1999). As previously mentioned, estradiol blunts the effects of hypoxia on erythropoietin production in women but has unclear significance in men and would not explain our findings; thus, another possibility is that these findings occurred by chance.
We scratched this topic, @FunkOdyssey, and @madman posted articles that explain the mechanism by which estradiol can influence hematocrit.
The open question is to what extent estrogens can increase hematocrit, and whether controlling estrogen levels can avoid or reduce high hematocrit levels.
Pathophysiology of testosterone therapy-associated erythrocytosis
The mechanisms underlying testosterone therapy-associated erythrocytosis are poorly understood.
Testosterone therapy has been associated with:
Dose-dependent decrease in hepcidin, which is hypothesized to increase absorption of iron, iron availability and erythropoiesis.
Increased erythropoietin levels.
Increased levels of estradiol, a breakdown product of testosterone via aromatase, which increases hematopoietic telomerase, resulting in increased hematopoietic stem cell proliferation and survival.
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