Aromatase Inhibitors (AIs)

Aromatase inhibitors (AIs) like anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin) are drugs that block the aromatase enzyme (CYP19A1), which normally converts androgens into estrogens. By inhibiting this conversion, AIs can sharply lower estrogen levels, which is why they’re a cornerstone therapy for estrogen-receptor–positive breast cancer, especially in postmenopausal women (1). This estrogen-deprivation effect commonly drives side effects that resemble an “artificial menopause,” including joint/muscle pain (AIMSS), hot flashes, vaginal dryness/sexual dysfunction, and bone loss (2).

Some people report that certain effects can be difficult to reverse or may persist even after stopping, and oncology references note that it’s not always clear whether sexual-function changes fully resolve after discontinuation in all patients (3). In online patient communities, you’ll also see the term “post-aromatase inhibitor syndrome” used to describe a persistent symptom pattern that people feel overlaps with PFS/PSSD/PAS (sexual dysfunction, mood/anhedonia changes, cognitive issues, etc.)—but this “post-AI syndrome” framing is largely anecdotal and not well defined in mainstream medical literature (4). For a PFS/PSSD/PAS audience, the practical takeaway is that AIs are high-impact hormone modulators and generally a high-risk category to avoid experimenting with, unless there’s a clear medical indication and close clinician oversight (5).

https://pmc.ncbi.nlm.nih.gov/articles/PMC4427607/

https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2021.713700/full

https://ascopubs.org/doi/10.14694/EdBook_AM.2015.35.e575

https://forum.propeciahelp.com/t/gents93-story-post-aromatase-inhibitor-syndrome/30804

https://pmc.ncbi.nlm.nih.gov/articles/PMC4427607/

Crash Anecdotes:

https://forum.propeciahelp.com/t/my-post-aromatase-inhibitor-syndrome-story/41990

https://forum.propeciahelp.com/t/another-possible-case-of-post-aromatase-inhibitor-syndrome/32700

My Personal Risk Ranking:

Moderate Risk of Permanent Worsening (for PFS/PSSD/PAS):

If you currently have PFS/PSSD/PAS, this substances may carry a moderate risk of worsening symptoms—potentially in a lasting way—and is best avoided due to AIs in rare cases resulting in a similar syndrome to PFS.