Burnett-Bowie SA et al. (2008) Effects of aromatase inhibition in hypogonadal older men: a randomized, double-blind, placebo-controlled trial. Clin Endocrinol (Oxf) [doi:10.1111/j.1365-2265.2008.03327.x]

Aromatase inhibition could be an alternative to testosterone administration to mitigate declining androgen production in hypogonadal older men. Unlike testosterone replacement, aromatase inhibition lowers circulating estradiol levels, which potentially prevents adverse effects of testosterone supplementation. Burnett-Bowie et al. investigated the efficacy and safety of the synthetic aromatase inhibitor anastrozole to treat hypogonadism in aging men.

The study enrolled 88 men (60 years or older) with symptoms of hypogonadism and low testosterone levels (5.2–10.4 nmol/l in a single measure or 10.4–12.1 nmol/l in two consecutive measures). Participants were randomly assigned to receive either anastrozole 1 mg daily or placebo for 12 months; 11 men from the anastrozole group and 8 from the placebo withdrew from the study. Changes in gonadal steroid hormone levels, lower extremity strength, body composition (fat and muscle), lipid levels, prostate-specific antigen levels, and symptoms of urinary obstruction were all recorded at baseline and every 3 months thereafter.

Compared with placebo and baseline measurements, aromatase inhibition increased mean serum testosterone levels by 50% at 3 months. However, mean androgen levels decreased between months 3 and 12 (but remained significantly higher than baseline), which indicated an acquired resistance to anastrozole. Conversely, anastrozole therapy lowered estradiol levels, which did not revert to baseline between months 3 and 12; no such change was observed in the placebo group.

Aromatase inhibition improved testosterone levels to the mid-normal range and did not alter prostate-specific antigen levels or urinary-obstructive symptoms, but failed to improve body composition or strength.