Anastrozole

Anastrozole is FDA-approved only for postmenopausal women with hormone-receptor-positive breast cancer. Use in men (to raise testosterone by blocking its conversion to estrogen) is entirely off-label — real trial data exists for this use, but it's outside the approved indication.

Human RCT (n=37 elderly men, 62-74 years, 12 weeks, testosterone <350 ng/dL): anastrozole (1mg daily or 1mg twice-weekly) raised total testosterone from a baseline of 343-397 ng/dL to 520-572 ng/dL (P<0.001 vs. placebo), with estradiol dropping from 26-27 to 17 pg/mL. Leder et al., J Clin Endocrinol Metab, 2004

Important honest finding: despite the substantial hormone changes, this same trial found no significant improvement in quality of life or sexual function — raising testosterone numbers didn't translate into how the men reported feeling or functioning over the 12-week period. The authors' own conclusion was that the physiological consequences of the hormonal changes "remain to be determined."

The human trial used 1mg daily or 1mg twice-weekly, orally — both raised testosterone significantly vs. placebo, and twice-weekly dosing achieved a similar effect to daily dosing with a lower cumulative dose.

In the same 12-week trial: hematocrit was unchanged, BPH symptom scores didn't change, but PSA increased in the twice-weekly group specifically (1.7 to 2.2 ng/mL, P=0.031 vs. placebo) — a real, specific safety signal worth noting rather than a generic "well tolerated" claim.