Aromatase inhibitors are often used to treat hypogonadism related to obesity and male infertility as they blocks the conversion of androgens to estrogens, raise plasma T/E2 ratio, and increases serum levels of LH, FSH, and testosterone.


To assess the effects of sustained aromatase inhibition in older hypogonadal men.
In a 1-year randomized, double-blind, placebo-controlled trial, 88 men, aged 60 and older with testosterone levels between 5.2 and 10.4 nmol/L on a single measure or between 10.4 and 12.1 nmol/L on two consecutive measures, and symptoms of hypogonadism were recruited. Subjects received either anastrozole 1 mg daily or placebo.
Changes in gonadal steroid hormone levels, body composition (by computerized tomography (CT) and dual x-ray absorptiometry (DXA)), strength, prostate specific antigen (PSA), symptoms of benign prostatic hypertrophy (BPH), hematocrit and lipid levels were assessed.
Testosterone levels increased from 11.2 +/- 3.3 nmol/L at baseline to 18.2 +/- 4.8 nmol/L at month 3 (p < 0.0001 vs. placebo) while bioavailable testosterone levels increased from 2.7 +/- 0.8 nmol/L at baseline to 5.4 +/- 1.7 nmol/L at month 3 (p < 0.0001 vs. placebo). Testosterone and biotestosterone levels peaked at month 3 and then declined by month 12 (though they remained significantly higher than baseline and greater than placebo). Estradiol levels decreased from 55.8 +/- 15.4 pmol/L at baseline to 42.2 +/- 13.6 pmol/L at month 3 and then remained stable (p < 0.0001). Body composition and strength did not change, nor did PSA, BPH symptoms, hematocrit or lipid levels.
Anastrozole administration normalized androgen production in older hypogonadal men and decreased estradiol production modestly. These alterations did not improve body composition or strength.