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Most circulating estradiol in men is derived from aromatized testosterone; thus, testosterone deficiency begets estradiol deficiency. In a U.S. study that involved 400 healthy male volunteers (age range, 20–50) with normal serum testosterone levels, researchers teased apart the effects of androgen and estrogen deficiencies.
First, participants received goserelin (Zoladex; the gonadotropin-releasing hormone analog), which lowered mean endogenous testosterone levels to <50 ng/dL. Next, participants were randomized to receive topical testosterone gel at doses of 1.25, 2.5, 5.0, or 10.0 g or placebo gel daily for 16 weeks. Half the men also received the aromatase inhibitor anastrozole, which created estradiol deficiency. Thus, the researchers cr…