Testosterone action on erythropoiesis does not require its aromatization to estrogen: Insights from the testosterone and estrogen treatment of two aromatase-deficient men.

Androgens act on erythropoiesis, but the relative role of testosterone (T) and estradiol (E2) on erythropoieticparameters in men is a poorly investigated issue. In order to evaluate separately the effects onerythropoiesis of high-dose T administration alone and of physiological dose of E2 administration alonetwo adult men with aromatase deficiency were assessed before and during each treatment. Blood cellcount, hemoglobin (Hb), hematocrit (Hct), erythrocyte mean cell volume (MCV), erythrocyte mean corpuscularhemoglobin (MCH), erythrocyte mean corpuscular hemoglobin concentration (MCHC), serumferritin, iron and total iron-binding capacity (TIBC), serum erythropoietin, serum total testosterone andestradiolwere evaluated. Hb, Hct and red cell count rose during testosterone treatment, consistently withthe increase in circulating testosterone, but failed to increase during estradiol treatment. A decrease inHb, Hct and red cell count was recorded in one of the two subjects during estradiol treatment, with aconcomitant decrease in serum testosterone. Circulating T alone is capable of and sufficient to influenceerythropoiesis, especially at supraphysiological dosage, while circulating E2 have not the same effecton erythropoietic parameters, suggesting the hypothesis that the erythropoietic changes induced byandrogens are not mediated via its aromatization to estrogens.