Could anastrozole indirectly harm parasites by changing hormone levels?

The short version: anastrozole could indirectly harm some parasites by lowering estrogen, but the evidence is limited to one tapeworm species in mice.

The 2002 study on Taenia crassiceps cysticercosis in mice is the only direct evidence in this retrieval [8]. It tested a different aromatase inhibitor (fadrozole, not anastrozole) and found that lowering estrogen shifted the immune response from a parasite-friendly TH2 profile toward a protective TH1 profile, reduced parasite burden, and reversed the feminization that the infection causes in male mice [8]. The effect was not direct: fadrozole did not kill cysticerci in a dish even at high doses [8]. It worked by changing the host's hormone environment and immune balance.

Anastrozole is the same class of drug as fadrozole (both are aromatase inhibitors that lower estrogen) [6]. The mechanism that helped against Taenia crassiceps would apply to any aromatase inhibitor. But the evidence stops there. No study in this retrieval tests anastrozole against any parasite. No study tests any aromatase inhibitor against human tapeworm infections, schistosomes, or other parasites that might depend on host estrogen.

The confidence is limited by the single species, the single drug, and the mouse model. The mechanism is plausible for any parasite whose survival depends on host estrogen or a TH2-skewed immune environment. But that is a long list of "ifs."

My call: anastrozole could indirectly harm some parasites by lowering host estrogen and shifting immunity, but the evidence is one mouse study of a related drug against one tapeworm species. Confidence: low.